enh: MDS FreeBSD: detect software mitigation as OK unless --paranoid (#503)

built from commit f5c42098c3
 dated 2026-04-06 00:17:32 +0200
 by Stéphane Lesimple (speed47_github@speed47.net)

.github/workflows/autoupdate.yml

@@ -5,6 +5,9 @@ on:
   schedule:
     - cron: '42 9 * * *'
 
+permissions:
+  pull-requests: write
+
 jobs:
   autoupdate:
     runs-on: ubuntu-latest
@@ -25,7 +28,6 @@ jobs:
         if: steps.diff.outputs.nbdiff != '0'
         uses: peter-evans/create-pull-request@v7
         with:
-          token: ${{ secrets.SMC_PR_PAT }}
           branch: autoupdate-fwdb
           commit-message: "update: fwdb from ${{ steps.diff.outputs.change }}, ${{ steps.diff.outputs.nbdiff }} microcode changes"
           title: "[Auto] Update fwdb from ${{ steps.diff.outputs.change }}"

.github/workflows/build.yml

@@ -0,0 +1,114 @@
+name: build
+
+on:
+  push:
+    branches:
+      - test
+      - source
+
+jobs:
+  build:
+
+    runs-on: ubuntu-latest
+
+    steps:
+    - uses: actions/checkout@v6
+      with:
+        persist-credentials: true
+    - name: install prerequisites
+      run: sudo apt-get update && sudo apt-get install -y shellcheck shfmt jq sqlite3 iucode-tool make
+    - name: update Intel model list
+      run: ./scripts/update_intel_models.sh
+    - name: build and check
+      run: |
+        make build fmt-check shellcheck
+        mv spectre-meltdown-checker.sh dist/
+    - name: check direct execution
+      run: |
+        expected=$(cat .github/workflows/expected_cve_count)
+        cd dist
+        nb=$(sudo ./spectre-meltdown-checker.sh --batch json | jq '.[]|.CVE' | wc -l)
+        if [ "$nb" -ne "$expected" ]; then
+          echo "Invalid number of CVEs reported: $nb instead of $expected"
+          exit 1
+        else
+          echo "OK $nb CVEs reported"
+        fi
+    - name: check docker compose run execution
+      run: |
+        expected=$(cat .github/workflows/expected_cve_count)
+        cd dist
+        docker compose build
+        nb=$(docker compose run --rm spectre-meltdown-checker --batch json | jq '.[]|.CVE' | wc -l)
+        if [ "$nb" -ne "$expected" ]; then
+          echo "Invalid number of CVEs reported: $nb instead of $expected"
+          exit 1
+        else
+          echo "OK $nb CVEs reported"
+        fi
+    - name: check docker run execution
+      run: |
+        expected=$(cat .github/workflows/expected_cve_count)
+        cd dist
+        docker build -t spectre-meltdown-checker .
+        nb=$(docker run --rm --privileged -v /boot:/boot:ro -v /dev/cpu:/dev/cpu:ro -v /lib/modules:/lib/modules:ro spectre-meltdown-checker --batch json | jq '.[]|.CVE' | wc -l)
+        if [ "$nb" -ne "$expected" ]; then
+          echo "Invalid number of CVEs reported: $nb instead of $expected"
+          exit 1
+        else
+          echo "OK $nb CVEs reported"
+        fi
+    - name: check fwdb update (separated)
+      run: |
+        cd dist
+        nbtmp1=$(find /tmp 2>/dev/null | wc -l)
+        ./spectre-meltdown-checker.sh --update-fwdb; ret=$?
+        if [ "$ret" != 0 ]; then
+          echo "Non-zero return value: $ret"
+          exit 1
+        fi
+        nbtmp2=$(find /tmp 2>/dev/null | wc -l)
+        if [ "$nbtmp1" != "$nbtmp2" ]; then
+          echo "Left temporary files!"
+          exit 1
+        fi
+        if ! [ -e ~/.mcedb ]; then
+          echo "No .mcedb file found after updating fwdb"
+          exit 1
+        fi
+    - name: check fwdb update (builtin)
+      run: |
+        cd dist
+        nbtmp1=$(find /tmp 2>/dev/null | wc -l)
+        ./spectre-meltdown-checker.sh --update-builtin-fwdb; ret=$?
+        if [ "$ret" != 0 ]; then
+          echo "Non-zero return value: $ret"
+          exit 1
+        fi
+        nbtmp2=$(find /tmp 2>/dev/null | wc -l)
+        if [ "$nbtmp1" != "$nbtmp2" ]; then
+          echo "Left temporary files!"
+          exit 1
+        fi
+    - name: create a pull request to ${{ github.ref_name }}-build
+      run: |
+        tmpdir=$(mktemp -d)
+        mv ./dist/* .github $tmpdir/
+        rm -rf ./dist
+        git fetch origin ${{ github.ref_name }}-build
+        git checkout -f ${{ github.ref_name }}-build
+        mv $tmpdir/* .
+        rm -rf src/
+        mkdir -p .github
+        rsync -vaP --delete $tmpdir/.github/ .github/
+        git add --all
+        echo =#=#= DIFF CACHED
+        git diff --cached
+        echo =#=#= STATUS
+        git status
+        echo =#=#= COMMIT
+        git config --global user.name "github-actions[bot]"
+        git config --global user.email "41898282+github-actions[bot]@users.noreply.github.com"
+        git log ${{ github.ref }} -1 --format=format:'%s%n%n built from commit %H%n dated %ai%n by %an (%ae)%n%n %b'
+        git log ${{ github.ref }} -1 --format=format:'%s%n%n built from commit %H%n dated %ai%n by %an (%ae)%n%n %b' | git commit -F -
+        git push

.github/workflows/expected_cve_count

@@ -0,0 +1 @@
+27

.github/workflows/stale.yml

@@ -0,0 +1,33 @@
+name: 'Manage stale issues and PRs'
+
+on:
+  schedule:
+    - cron: '37 7 * * *'
+  workflow_dispatch:
+    inputs:
+      action:
+        description: "dry-run"
+        required: true
+        default: "dryrun"
+        type: choice
+        options:
+          - dryrun
+          - apply
+
+permissions:
+  issues: write
+  pull-requests: write
+
+jobs:
+  stale:
+    runs-on: ubuntu-latest
+    steps:
+      - uses: actions/stale@v10
+        with:
+          any-of-labels: 'needs-more-info,answered'
+          labels-to-remove-when-unstale: 'needs-more-info,answered'
+          days-before-stale: 30
+          days-before-close: 7
+          stale-issue-label: stale
+          remove-stale-when-updated: true
+          debug-only: ${{ case(inputs.action == 'dryrun', true, false) }}

README.md

@@ -16,18 +16,24 @@ CVE | Name | Aliases
 [CVE-2018-3620](https://cve.mitre.org/cgi-bin/cvename.cgi?name=CVE-2018-3620) | L1 Terminal Fault | Foreshadow-NG (OS/SMM)
 [CVE-2018-3646](https://cve.mitre.org/cgi-bin/cvename.cgi?name=CVE-2018-3646) | L1 Terminal Fault | Foreshadow-NG (VMM)
 [CVE-2018-12126](https://cve.mitre.org/cgi-bin/cvename.cgi?name=CVE-2018-12126) | Microarchitectural Store Buffer Data Sampling | MSBDS, Fallout
-[CVE-2018-12130](https://cve.mitre.org/cgi-bin/cvename.cgi?name=CVE-2018-12130) | Microarchitectural Fill Buffer Data Sampling | MFBDS, ZombieLoad
 [CVE-2018-12127](https://cve.mitre.org/cgi-bin/cvename.cgi?name=CVE-2018-12127) | Microarchitectural Load Port Data Sampling | MLPDS, RIDL
+[CVE-2018-12130](https://cve.mitre.org/cgi-bin/cvename.cgi?name=CVE-2018-12130) | Microarchitectural Fill Buffer Data Sampling | MFBDS, ZombieLoad
+[CVE-2018-12207](https://cve.mitre.org/cgi-bin/cvename.cgi?name=CVE-2018-12207) | Machine Check Exception on Page Size Changes | iTLB Multihit, No eXcuses
 [CVE-2019-11091](https://cve.mitre.org/cgi-bin/cvename.cgi?name=CVE-2019-11091) | Microarchitectural Data Sampling Uncacheable Memory | MDSUM, RIDL
 [CVE-2019-11135](https://cve.mitre.org/cgi-bin/cvename.cgi?name=CVE-2019-11135) | TSX Asynchronous Abort | TAA, ZombieLoad V2
-[CVE-2018-12207](https://cve.mitre.org/cgi-bin/cvename.cgi?name=CVE-2018-12207) | Machine Check Exception on Page Size Changes | iTLB Multihit, No eXcuses
 [CVE-2020-0543](https://cve.mitre.org/cgi-bin/cvename.cgi?name=CVE-2020-0543) | Special Register Buffer Data Sampling | SRBDS, CROSSTalk
+[CVE-2022-29900](https://cve.mitre.org/cgi-bin/cvename.cgi?name=CVE-2022-29900) | Arbitrary Speculative Code Execution with Return Instructions | Retbleed (AMD)
+[CVE-2022-29901](https://cve.mitre.org/cgi-bin/cvename.cgi?name=CVE-2022-29901) | Arbitrary Speculative Code Execution with Return Instructions | Retbleed (Intel), RSBA
 [CVE-2022-40982](https://cve.mitre.org/cgi-bin/cvename.cgi?name=CVE-2022-40982) | Gather Data Sampling | Downfall, GDS
 [CVE-2023-20569](https://cve.mitre.org/cgi-bin/cvename.cgi?name=CVE-2023-20569) | Return Address Security | Inception, SRSO
 [CVE-2023-20593](https://cve.mitre.org/cgi-bin/cvename.cgi?name=CVE-2023-20593) | Cross-Process Information Leak | Zenbleed
 [CVE-2023-23583](https://cve.mitre.org/cgi-bin/cvename.cgi?name=CVE-2023-23583) | Redundant Prefix Issue | Reptar
+[CVE-2023-28746](https://cve.mitre.org/cgi-bin/cvename.cgi?name=CVE-2023-28746) | Register File Data Sampling | RFDS
+[CVE-2024-28956](https://cve.mitre.org/cgi-bin/cvename.cgi?name=CVE-2024-28956) | Indirect Target Selection | ITS
 [CVE-2024-36350](https://cve.mitre.org/cgi-bin/cvename.cgi?name=CVE-2024-36350) | Transient Scheduler Attack, Store Queue | TSA-SQ
 [CVE-2024-36357](https://cve.mitre.org/cgi-bin/cvename.cgi?name=CVE-2024-36357) | Transient Scheduler Attack, L1 | TSA-L1
+[CVE-2025-40300](https://cve.mitre.org/cgi-bin/cvename.cgi?name=CVE-2025-40300) | VM-Exit Stale Branch Prediction | VMScape
+[CVE-2024-45332](https://cve.mitre.org/cgi-bin/cvename.cgi?name=CVE-2024-45332) | Branch Privilege Injection | BPI
 
 ## Am I at risk?
 
@@ -45,18 +51,24 @@ CVE-2018-3615 (Foreshadow, SGX) | ✅ (3) | ✅ (3) | ✅ (3) | ✅ (3) | Microc
 CVE-2018-3620 (Foreshadow-NG, OS/SMM) | 💥 | ✅ | ✅ | ✅ | Kernel update
 CVE-2018-3646 (Foreshadow-NG, VMM) | ✅ | ✅ | 💥 | 💥 | Kernel update (or disable EPT/SMT)
 CVE-2018-12126 (MSBDS, Fallout) | 💥 | 💥 (1) | 💥 | 💥 (1) | Microcode + kernel update
-CVE-2018-12130 (MFBDS, ZombieLoad) | 💥 | 💥 (1) | 💥 | 💥 (1) | Microcode + kernel update
 CVE-2018-12127 (MLPDS, RIDL) | 💥 | 💥 (1) | 💥 | 💥 (1) | Microcode + kernel update
+CVE-2018-12130 (MFBDS, ZombieLoad) | 💥 | 💥 (1) | 💥 | 💥 (1) | Microcode + kernel update
+CVE-2018-12207 (iTLB Multihit, No eXcuses) | ✅ | ✅ | ☠️ | ✅ | Hypervisor update (or disable hugepages)
 CVE-2019-11091 (MDSUM, RIDL) | 💥 | 💥 (1) | 💥 | 💥 (1) | Microcode + kernel update
 CVE-2019-11135 (TAA, ZombieLoad V2) | 💥 | 💥 (1) | 💥 | 💥 (1) | Microcode + kernel update
-CVE-2018-12207 (iTLB Multihit, No eXcuses) | ✅ | ✅ | ☠️ | ✅ | Hypervisor update (or disable hugepages)
 CVE-2020-0543 (SRBDS, CROSSTalk) | 💥 (2) | 💥 (2) | 💥 (2) | 💥 (2) | Microcode + kernel update
+CVE-2022-29900 (Retbleed AMD) | 💥 | ✅ | 💥 | ✅ | Kernel update (+ microcode for IBPB)
+CVE-2022-29901 (Retbleed Intel, RSBA) | 💥 | ✅ | 💥 | ✅ | Microcode + kernel update (eIBRS or IBRS)
 CVE-2022-40982 (Downfall, GDS) | 💥 | 💥 | 💥 | 💥 | Microcode update (or disable AVX)
 CVE-2023-20569 (Inception, SRSO) | 💥 | ✅ | 💥 | ✅ | Microcode + kernel update
 CVE-2023-20593 (Zenbleed) | 💥 | 💥 | 💥 | 💥 | Microcode update (or kernel workaround)
 CVE-2023-23583 (Reptar) | ☠️ | ☠️ | ☠️ | ☠️ | Microcode update
+CVE-2023-28746 (RFDS) | 💥 | ✅ | 💥 | ✅ | Microcode + kernel update
+CVE-2024-28956 (ITS) | 💥 | ✅ | 💥 (4) | ✅ | Microcode + kernel update
 CVE-2024-36350 (TSA-SQ) | 💥 | 💥 (1) | 💥 | 💥 (1) | Microcode + kernel update
 CVE-2024-36357 (TSA-L1) | 💥 | 💥 (1) | 💥 | 💥 (1) | Microcode + kernel update
+CVE-2025-40300 (VMScape) | ✅ | ✅ | 💥 | ✅ | Kernel update (IBPB on VM-exit)
+CVE-2024-45332 (BPI) | 💥 | ✅ | 💥 | ✅ | Microcode update
 
 > 💥 Data can be leaked across this boundary.
 
@@ -70,6 +82,8 @@ CVE-2024-36357 (TSA-L1) | 💥 | 💥 (1) | 💥 | 💥 (1) | Microcode + kernel
 
 > (3) CVE-2018-3615 (Foreshadow SGX) inverts the normal trust model: the OS reads SGX enclave data. It is irrelevant unless the system runs SGX enclaves, and the attacker must already have OS-level access.
 
+> (4) VM→Host leakage applies only to certain affected CPU models (Skylake-X, Kaby Lake, Comet Lake). Ice Lake, Tiger Lake, and Rocket Lake are only affected for native (user-to-kernel) attacks, not guest-to-host.
+
 ## Detailed CVE descriptions
 
 <details>
@@ -109,26 +123,34 @@ A guest VM can exploit L1TF to read memory belonging to the host or other guests
 
 **CVE-2018-12126 — Microarchitectural Store Buffer Data Sampling (MSBDS, Fallout)**
 
-**CVE-2018-12130 — Microarchitectural Fill Buffer Data Sampling (MFBDS, ZombieLoad)**
-
 **CVE-2018-12127 — Microarchitectural Load Port Data Sampling (MLPDS, RIDL)**
 
+**CVE-2018-12130 — Microarchitectural Fill Buffer Data Sampling (MFBDS, ZombieLoad)**
+
 **CVE-2019-11091 — Microarchitectural Data Sampling Uncacheable Memory (MDSUM, RIDL)**
 
 These four CVEs are collectively known as "MDS" (Microarchitectural Data Sampling) vulnerabilities. They exploit different CPU internal buffers — store buffer, fill buffer, load ports, and uncacheable memory paths — that can leak recently accessed data across privilege boundaries during speculative execution. An unprivileged attacker can observe data recently processed by the kernel or other processes. Mitigation requires a microcode update (providing the MD_CLEAR mechanism) plus a kernel update that uses VERW to clear affected buffers on privilege transitions. Disabling Hyper-Threading (SMT) provides additional protection because sibling threads share these buffers. The performance impact is low to significant, depending on the frequency of kernel transitions and whether SMT is disabled.
 
-**CVE-2019-11135 — TSX Asynchronous Abort (TAA, ZombieLoad V2)**
-
-On CPUs with Intel TSX, a transactional abort can leave data from the line fill buffers in a state observable through side channels, similar to the MDS vulnerabilities but triggered through TSX. Mitigation requires a microcode update plus kernel support to either clear affected buffers or disable TSX entirely (via the TSX_CTRL MSR). The performance impact is low to significant, similar to MDS, with the option to eliminate the attack surface entirely by disabling TSX at the cost of losing transactional memory support.
-
 **CVE-2018-12207 — Machine Check Exception on Page Size Changes (iTLB Multihit, No eXcuses)**
 
 A malicious guest VM can trigger a machine check exception (MCE) — crashing the entire host — by creating specific conditions in the instruction TLB involving page size changes. This is a denial-of-service vulnerability affecting hypervisors running untrusted guests. Mitigation requires either disabling hugepage use in the hypervisor or updating the hypervisor to avoid the problematic iTLB configurations. The performance impact ranges from low to significant depending on the approach: disabling hugepages can substantially impact memory-intensive workloads.
 
+**CVE-2019-11135 — TSX Asynchronous Abort (TAA, ZombieLoad V2)**
+
+On CPUs with Intel TSX, a transactional abort can leave data from the line fill buffers in a state observable through side channels, similar to the MDS vulnerabilities but triggered through TSX. Mitigation requires a microcode update plus kernel support to either clear affected buffers or disable TSX entirely (via the TSX_CTRL MSR). The performance impact is low to significant, similar to MDS, with the option to eliminate the attack surface entirely by disabling TSX at the cost of losing transactional memory support.
+
 **CVE-2020-0543 — Special Register Buffer Data Sampling (SRBDS, CROSSTalk)**
 
 Certain special CPU instructions (RDRAND, RDSEED, EGETKEY) read data through a shared staging buffer that is accessible across all cores via speculative execution. An attacker running code on any core can observe the output of these instructions from a victim on a different core, including extracting cryptographic keys from SGX enclaves (a complete ECDSA key was demonstrated). This is notable as one of the first cross-core speculative execution attacks. Mitigation requires a microcode update that serializes access to the staging buffer, plus a kernel update to manage the mitigation. Performance impact is low, mainly affecting workloads that heavily use RDRAND/RDSEED.
 
+**CVE-2022-29900 — Arbitrary Speculative Code Execution with Return Instructions (Retbleed AMD)**
+
+On AMD processors from families 0x15 through 0x17 (Bulldozer through Zen 2) and Hygon family 0x18, an attacker can exploit return instructions to redirect speculative execution and leak kernel memory, bypassing retpoline mitigations that were effective against Spectre V2. Unlike Spectre V2 which targets indirect jumps and calls, Retbleed specifically targets return instructions, which were previously considered safe. Mitigation requires a kernel update providing either the untrained return thunk (safe RET) or IBPB-on-entry mechanism, plus a microcode update providing IBPB support on Zen 1/2. On Zen 1/2, SMT should be disabled for full protection when using IBPB-based mitigation. Performance impact is medium.
+
+**CVE-2022-29901 — Arbitrary Speculative Code Execution with Return Instructions (Retbleed Intel, RSBA)**
+
+On Intel Skylake through Rocket Lake processors with RSB Alternate Behavior (RSBA), return instructions can be speculatively redirected via the Branch Target Buffer when the Return Stack Buffer underflows, bypassing retpoline mitigations. Mitigation requires either Enhanced IBRS (eIBRS, via microcode update) or a kernel compiled with IBRS-on-entry support (Linux 5.19+). Call depth tracking (stuffing) is an alternative mitigation available from Linux 6.2+. Plain retpoline does NOT mitigate this vulnerability on RSBA-capable CPUs. Performance impact is medium to high.
+
 **CVE-2022-40982 — Gather Data Sampling (GDS, Downfall)**
 
 The AVX GATHER instructions can leak data from previously used vector registers across privilege boundaries through the shared gather data buffer. This affects any software using AVX2 or AVX-512 on vulnerable Intel processors. Mitigation is provided by a microcode update that clears the gather buffer, or alternatively by disabling the AVX feature entirely. Performance impact is negligible for most workloads but can be significant (up to 50%) for AVX-heavy applications such as HPC and AI inference.
@@ -145,6 +167,14 @@ A bug in AMD Zen 2 processors causes the VZEROUPPER instruction to incorrectly z
 
 A bug in Intel processors causes unexpected behavior when executing instructions with specific redundant REX prefixes. Depending on the circumstances, this can result in a system crash (MCE), unpredictable behavior, or potentially privilege escalation. Any software running on an affected CPU can trigger the bug. Mitigation requires a microcode update. Performance impact is low.
 
+**CVE-2023-28746 — Register File Data Sampling (RFDS)**
+
+On certain Intel Atom and hybrid processors (Goldmont, Goldmont Plus, Tremont, Gracemont, and the Atom cores of Alder Lake and Raptor Lake), the register file can retain stale data from previous operations that is accessible via speculative execution, allowing an attacker to infer data across privilege boundaries. Mitigation requires both a microcode update (providing the RFDS_CLEAR capability) and a kernel update (CONFIG_MITIGATION_RFDS, Linux 6.9+) that uses the VERW instruction to clear the register file on privilege transitions. CPUs with the RFDS_NO capability bit are not affected. Performance impact is low.
+
+**CVE-2024-28956 — Indirect Target Selection (ITS)**
+
+On certain Intel processors (Skylake-X stepping 6+, Kaby Lake, Comet Lake, Ice Lake, Tiger Lake, Rocket Lake), an attacker can train the indirect branch predictor to speculatively execute a targeted gadget in the kernel, bypassing eIBRS protections. The Branch Target Buffer (BTB) uses only partial address bits to index indirect branch targets, allowing user-space code to influence kernel-space speculative execution. Some affected CPUs (Ice Lake, Tiger Lake, Rocket Lake) are only vulnerable to native user-to-kernel attacks, not guest-to-host (VMX) attacks. Mitigation requires both a microcode update (IPU 2025.1 / microcode-20250512+, which fixes IBPB to fully flush indirect branch predictions) and a kernel update (CONFIG_MITIGATION_ITS, Linux 6.15+) that aligns branch/return thunks or uses RSB stuffing. Performance impact is low.
+
 **CVE-2024-36350 — Transient Scheduler Attack, Store Queue (TSA-SQ)**
 
 On AMD Zen 3 and Zen 4 processors, the CPU's transient scheduler may speculatively retrieve stale data from the store queue during certain timing windows, allowing an attacker to infer data from previous store operations across privilege boundaries. The attack can also leak data between SMT sibling threads. Mitigation requires both a microcode update (exposing the VERW_CLEAR capability) and a kernel update (CONFIG_MITIGATION_TSA, Linux 6.16+) that uses the VERW instruction to clear CPU buffers on user/kernel transitions and before VMRUN. The kernel also clears buffers on idle when SMT is active. Performance impact is low to medium.
@@ -153,8 +183,23 @@ On AMD Zen 3 and Zen 4 processors, the CPU's transient scheduler may speculative
 
 On AMD Zen 3 and Zen 4 processors, the CPU's transient scheduler may speculatively retrieve stale data from the L1 data cache during certain timing windows, allowing an attacker to infer data in the L1D cache across privilege boundaries. Mitigation requires the same microcode and kernel updates as TSA-SQ: a microcode update exposing VERW_CLEAR and a kernel update (CONFIG_MITIGATION_TSA, Linux 6.16+) that clears CPU buffers via VERW on privilege transitions. Performance impact is low to medium.
 
+**CVE-2025-40300 — VM-Exit Stale Branch Prediction (VMScape)**
+
+After a guest VM exits to the host, stale branch predictions from the guest can influence host-side speculative execution before the kernel returns to userspace, allowing a local attacker to leak host kernel memory. This affects Intel processors from Sandy Bridge through Arrow Lake/Lunar Lake, AMD Zen 1 through Zen 5 families, and Hygon family 0x18. Only systems running a hypervisor with untrusted guests are at risk. Mitigation requires a kernel update (CONFIG_MITIGATION_VMSCAPE, Linux 6.18+) that issues IBPB before returning to userspace after a VM exit. No specific microcode update is required beyond existing IBPB support. Performance impact is low.
+
+**CVE-2024-45332 — Branch Privilege Injection (BPI)**
+
+A race condition in the branch predictor update mechanism of Intel processors (Coffee Lake through Raptor Lake, plus some server and Atom parts) allows user-space branch predictions to briefly influence kernel-space speculative execution, undermining eIBRS and IBPB protections. This means systems relying solely on eIBRS for Spectre V2 mitigation may not be fully protected without the microcode fix. Mitigation requires a microcode update (intel-microcode 20250512+) that fixes the asynchronous branch predictor update timing so that eIBRS and IBPB work as originally intended. No kernel changes are required. Performance impact is negligible.
+
 </details>
 
+## Unsupported CVEs
+
+Several transient execution CVEs are not covered by this tool, for various reasons (duplicates, only
+affecting non-supported hardware or OS, theoretical with no known exploitation, etc.).
+The complete list along with the reason for each exclusion is available in the
+[UNSUPPORTED_CVE_LIST.md](https://github.com/speed47/spectre-meltdown-checker/blob/source/UNSUPPORTED_CVE_LIST.md) file.
+
 ## Scope
 
 Supported operating systems: