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CVE-2026-63940

CRITICAL 9.3 ALL-YEARS

Published 2026-07-19 · Last modified 2026-10-21 · Linux · NVD: Undergoing Analysis

In the Linux kernel, the following vulnerability has been resolved: KVM: SEV: Ignore Port I/O requests of length '0' Explicitly ignore Port I/O requests of length '0' (or count '0'), so that setting up the software scratch area (and other code) doesn't have to worry about underflowing the length, and to allow for WARNing on trying to configure the scratch area with len==0.

ELEVATED IMPACT

Severe if exploited (CVSS 9.3), but no confirmed exploitation. Patch on a normal cadence.

Exploitation likelihood

0.2%chance of exploitation in 30 days · 8th percentile

○ In CISA KEV○ Catalogued PoC◆ SSVC: exploitation none, automatable no

Impact if exploited

9.3CVSS 3.1 · CRITICAL · CNA

  • ConfidentialityHigh
  • IntegrityHigh
  • AvailabilityHigh

What an attacker needs

  • ⚠Access: Requires local access to the host
  • ✓Privileges: No account or privileges required
  • ✓User interaction: No user interaction needed
  • ✓Complexity: No special conditions — reliably repeatable

✓ lowers the bar for an attacker · ⚠ raises it

Proof of concept

No public PoC is currently catalogued.

Search for new PoCs

Search GitHub now — results may be empty or unverified.

Tracked sources are checked weekly for the full archive, including PoCs published after the original disclosure. A later release appears after a tracked source lists it and a refresh succeeds.

Affected

Vendors Linux

Products Linux

Weakness (CWE)

  • CWE-190: Integer Overflow or Wraparound

CVSS vector

CVSS:3.1/AV:L/AC:L/PR:N/UI:N/S:C/C:H/I:H/A:H

References and research data (JSON)

Vendor product assessments

Showing 32 of 274 vendor product statements; 242 omitted. Read the full vendor advisory.

  • kernel as a component of Red Hat Enterprise Linux 10 · known affected

    Vendor assessment for this product only.

    pkg:rpm/redhat/kernel

    • none available: Affected
    Red Hat · CVE-2026-63940 · Updated 2026-08-05T14:21:14+00:00
  • kernel-abi-stablelists as a component of Red Hat Enterprise Linux 10 · known affected

    Vendor assessment for this product only.

    pkg:rpm/redhat/kernel-abi-stablelists

    • none available: Affected
    Red Hat · CVE-2026-63940 · Updated 2026-08-05T14:21:14+00:00
  • kernel-modules-extra-matched as a component of Red Hat Enterprise Linux 10 · known affected

    Vendor assessment for this product only.

    pkg:rpm/redhat/kernel-modules-extra-matched

    • none available: Affected
    Red Hat · CVE-2026-63940 · Updated 2026-08-05T14:21:14+00:00
  • kernel-rt-debug as a component of Red Hat Enterprise Linux 10 · known affected

    Vendor assessment for this product only.

    pkg:rpm/redhat/kernel-rt-debug

    • none available: Affected
    Red Hat · CVE-2026-63940 · Updated 2026-08-05T14:21:14+00:00
  • kernel-uki-virt-addons as a component of Red Hat Enterprise Linux 10 · known affected

    Vendor assessment for this product only.

    pkg:rpm/redhat/kernel-uki-virt-addons

    • none available: Affected
    Red Hat · CVE-2026-63940 · Updated 2026-08-05T14:21:14+00:00
  • kernel as a component of Red Hat Enterprise Linux 8 · known affected

    Vendor assessment for this product only.

    pkg:rpm/redhat/kernel

    • none available: Affected
    Red Hat · CVE-2026-63940 · Updated 2026-08-05T14:21:14+00:00
  • kernel-modules as a component of Red Hat Enterprise Linux 8 · known affected

    Vendor assessment for this product only.

    pkg:rpm/redhat/kernel-modules

    • none available: Affected
    Red Hat · CVE-2026-63940 · Updated 2026-08-05T14:21:14+00:00
  • kernel-rt-modules-internal as a component of Red Hat Enterprise Linux 8 · known affected

    Vendor assessment for this product only.

    pkg:rpm/redhat/kernel-rt-modules-internal

    • none available: Affected
    Red Hat · CVE-2026-63940 · Updated 2026-08-05T14:21:14+00:00
  • python3-perf as a component of Red Hat Enterprise Linux 8 · known affected

    Vendor assessment for this product only.

    pkg:rpm/redhat/python3-perf

    • none available: Affected
    Red Hat · CVE-2026-63940 · Updated 2026-08-05T14:21:14+00:00
  • kernel-64k-modules as a component of Red Hat Enterprise Linux 9 · known affected

    Vendor assessment for this product only.

    pkg:rpm/redhat/kernel-64k-modules

    • none available: Affected
    Red Hat · CVE-2026-63940 · Updated 2026-08-05T14:21:14+00:00
  • kernel-debug-modules-internal as a component of Red Hat Enterprise Linux 9 · known affected

    Vendor assessment for this product only.

    pkg:rpm/redhat/kernel-debug-modules-internal

    • none available: Affected
    Red Hat · CVE-2026-63940 · Updated 2026-08-05T14:21:14+00:00
  • kernel-rt-64k as a component of Red Hat Enterprise Linux 9 · known affected

    Vendor assessment for this product only.

    pkg:rpm/redhat/kernel-rt-64k

    • none available: Affected
    Red Hat · CVE-2026-63940 · Updated 2026-08-05T14:21:14+00:00
  • kernel-rt-64k-modules-core as a component of Red Hat Enterprise Linux 9 · known affected

    Vendor assessment for this product only.

    pkg:rpm/redhat/kernel-rt-64k-modules-core

    • none available: Affected
    Red Hat · CVE-2026-63940 · Updated 2026-08-05T14:21:14+00:00
  • kernel-rt-devel as a component of Red Hat Enterprise Linux 9 · known affected

    Vendor assessment for this product only.

    pkg:rpm/redhat/kernel-rt-devel

    • none available: Affected
    Red Hat · CVE-2026-63940 · Updated 2026-08-05T14:21:14+00:00
  • kernel-zfcpdump as a component of Red Hat Enterprise Linux 9 · known affected

    Vendor assessment for this product only.

    pkg:rpm/redhat/kernel-zfcpdump

    • none available: Affected
    Red Hat · CVE-2026-63940 · Updated 2026-08-05T14:21:14+00:00
  • rv as a component of Red Hat Enterprise Linux 9 · known affected

    Vendor assessment for this product only.

    pkg:rpm/redhat/rv

    • none available: Affected
    Red Hat · CVE-2026-63940 · Updated 2026-08-05T14:21:14+00:00
  • kernel as a component of Red Hat Enterprise Linux 6 · known not affected

    Vendor assessment for this product only.

    Reason: vulnerable code not present

    pkg:rpm/redhat/kernel

    Red Hat · CVE-2026-63940 · Updated 2026-08-05T14:21:14+00:00
  • kernel-debug as a component of Red Hat Enterprise Linux 6 · known not affected

    Vendor assessment for this product only.

    Reason: vulnerable code not present

    pkg:rpm/redhat/kernel-debug

    Red Hat · CVE-2026-63940 · Updated 2026-08-05T14:21:14+00:00
  • kernel-devel as a component of Red Hat Enterprise Linux 6 · known not affected

    Vendor assessment for this product only.

    Reason: vulnerable code not present

    pkg:rpm/redhat/kernel-devel

    Red Hat · CVE-2026-63940 · Updated 2026-08-05T14:21:14+00:00
  • kernel-headers as a component of Red Hat Enterprise Linux 6 · known not affected

    Vendor assessment for this product only.

    Reason: vulnerable code not present

    pkg:rpm/redhat/kernel-headers

    Red Hat · CVE-2026-63940 · Updated 2026-08-05T14:21:14+00:00
  • kernel.src as a component of Red Hat Enterprise Linux 6 · known not affected

    Vendor assessment for this product only.

    Reason: vulnerable code not present

    pkg:rpm/redhat/kernel?arch=src

    Red Hat · CVE-2026-63940 · Updated 2026-08-05T14:21:14+00:00
  • bpftool as a component of Red Hat Enterprise Linux 7 · known not affected

    Vendor assessment for this product only.

    Reason: vulnerable code not present

    pkg:rpm/redhat/bpftool

    Red Hat · CVE-2026-63940 · Updated 2026-08-05T14:21:14+00:00
  • kernel-abi-whitelists as a component of Red Hat Enterprise Linux 7 · known not affected

    Vendor assessment for this product only.

    Reason: vulnerable code not present

    pkg:rpm/redhat/kernel-abi-whitelists

    Red Hat · CVE-2026-63940 · Updated 2026-08-05T14:21:14+00:00
  • kernel-debug-devel as a component of Red Hat Enterprise Linux 7 · known not affected

    Vendor assessment for this product only.

    Reason: vulnerable code not present

    pkg:rpm/redhat/kernel-debug-devel

    Red Hat · CVE-2026-63940 · Updated 2026-08-05T14:21:14+00:00
  • kernel-headers as a component of Red Hat Enterprise Linux 7 · known not affected

    Vendor assessment for this product only.

    Reason: vulnerable code not present

    pkg:rpm/redhat/kernel-headers

    Red Hat · CVE-2026-63940 · Updated 2026-08-05T14:21:14+00:00
  • kernel-rt as a component of Red Hat Enterprise Linux 7 · known not affected

    Vendor assessment for this product only.

    Reason: vulnerable code not present

    pkg:rpm/redhat/kernel-rt

    Red Hat · CVE-2026-63940 · Updated 2026-08-05T14:21:14+00:00
  • kernel-rt-debug-devel as a component of Red Hat Enterprise Linux 7 · known not affected

    Vendor assessment for this product only.

    Reason: vulnerable code not present

    pkg:rpm/redhat/kernel-rt-debug-devel

    Red Hat · CVE-2026-63940 · Updated 2026-08-05T14:21:14+00:00
  • kernel-rt-doc as a component of Red Hat Enterprise Linux 7 · known not affected

    Vendor assessment for this product only.

    Reason: vulnerable code not present

    pkg:rpm/redhat/kernel-rt-doc

    Red Hat · CVE-2026-63940 · Updated 2026-08-05T14:21:14+00:00
  • kernel-rt-trace-devel as a component of Red Hat Enterprise Linux 7 · known not affected

    Vendor assessment for this product only.

    Reason: vulnerable code not present

    pkg:rpm/redhat/kernel-rt-trace-devel

    Red Hat · CVE-2026-63940 · Updated 2026-08-05T14:21:14+00:00
  • kernel-tools as a component of Red Hat Enterprise Linux 7 · known not affected

    Vendor assessment for this product only.

    Reason: vulnerable code not present

    pkg:rpm/redhat/kernel-tools

    Red Hat · CVE-2026-63940 · Updated 2026-08-05T14:21:14+00:00
  • kernel-tools-libs-devel as a component of Red Hat Enterprise Linux 7 · known not affected

    Vendor assessment for this product only.

    Reason: vulnerable code not present

    pkg:rpm/redhat/kernel-tools-libs-devel

    Red Hat · CVE-2026-63940 · Updated 2026-08-05T14:21:14+00:00
  • python-perf as a component of Red Hat Enterprise Linux 7 · known not affected

    Vendor assessment for this product only.

    Reason: vulnerable code not present

    pkg:rpm/redhat/python-perf

    Red Hat · CVE-2026-63940 · Updated 2026-08-05T14:21:14+00:00

All CVSS metrics

  • CRITICAL 9.3 v3.1 · CNA Primary
    CVSS:3.1/AV:L/AC:L/PR:N/UI:N/S:C/C:H/I:H/A:H
  • CRITICAL 9.3 v3.1 · NVD Secondary
    CVSS:3.1/AV:L/AC:L/PR:N/UI:N/S:C/C:H/I:H/A:H

References

Advisories

Technical & other

Sources: NVD · CVE.org · All sources and attribution · EPSS