DaystoPatch

Linux kernelExploited incident

Linux kernel AF_ALG concurrent-write race in af_alg_sendmsg (CVE-2025-39964)

CVE-2025-39964High, CVSS 7.8In CISA's Known Exploited Vulnerabilities catalog since 18 Sep 2026

  • Exploited after a fix existed
FixedA fix existed when the bug went public. No evidence yet of when every version was fixed.

Response

Silence
0h
First public report to first vendor statement
Exposure
0h
First public report to first fix
Follow-through
not dated
First public report to a fix for every supported version
  • Vendor silent
  • Vendor statement, no fix
  • Fixed for some versions
  • Fixed when disclosed
  • Date only, no time of day

Timeline and evidence

Open a moment to see its source and archived quote.

  1. First public report

    CVE-2025-39964 record (CNA: Linux)CuratedQuote verified

    "datePublished":"2025-10-13T13:48:30.334Z"

    CVE title: 'crypto: af_alg - Disallow concurrent writes in af_alg_sendmsg'.

    Recorded time
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    To the minute
    Origin
    Curated. Found by a researcher, with a verbatim quote and link.
    Quote check
    Found in the archived copy
    Snapshot
    sha256:e1feb905eee8dd63…
    Used in metrics
    Yes
    Dispute this timestamp
    6 more sources for this moment
    CVE.org record CVE-2025-39964ClaimedQuote verified13 Oct 2025, 13:48 UTC

    In the Linux kernel, the following vulnerability has been resolved:

    CVE record published.

    Recorded time
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    Origin
    Claimed. The date the source gives.
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    Found in the archived copy
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    sha256:e1feb905eee8dd63…
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    No, kept for the record
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    Bluesky postClaimedQuote not checked yet11 Dec 2025, 03:40 UTC

    (CVE-2025-39946, CVE-2025-39964, CVE-2025-39993, CVE-2025-40018)

    Earliest third-party post we hold.

    Source
    Bluesky post social
    Recorded time
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    To the minute
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    Claimed. The date the source gives.
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    Not checked yet
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    No archived snapshot
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    No, kept for the record
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    CISA KEV (CVE-2025-39964)ClaimedQuote verified18 Sep 2026

    Linux Kernel Race Condition Vulnerability

    Added to CISA's KEV catalog on 2026-09-18.

    Recorded time
    Precision
    Date only (no time of day is shown)
    Origin
    Claimed. The date the source gives.
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    Found in the archived copy
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    sha256:ef8fffede5c47200…
    Used in metrics
    No, kept for the record
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    Mastodon postClaimedQuote not checked yet18 Sep 2026, 15:00 UTC

    🚨 [CISA-2026:0918] CISA Adds 2 Known Exploited Vulnerabilities to Catalog ( https:// secdb.nttzen.cloud/security-ad visory/detail/CISA-2026:0918 ) CISA has added 2 new vulnerabilities to its Known

    Earliest third-party post we hold.

    Source
    Mastodon post social
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    To the minute
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    Claimed. The date the source gives.
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    Not checked yet
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    No archived snapshot
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    Hacker NewsClaimedQuote not checked yet24 Sep 2026, 16:56 UTC

    CISA active Linux kernel CVEs (CVE-2025-39964, CVE-2026-53266, CVE-2025-39682)

    Earliest third-party post we hold.

    Source
    Hacker News hn
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    To the minute
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    Claimed. The date the source gives.
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    Not checked yet
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    News: cisa_advisoriesClaimedQuote verified22 Oct 2026

    Siemens SIMATIC S7-1500 CPU 1518(F)-4 PN/DP MFP

    Earliest mention we hold (a vetted outlet).

    Recorded time
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    Date only (no time of day is shown)
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    Claimed. The date the source gives.
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    Found in the archived copy
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    sha256:70d5c723906ec426…
    Used in metrics
    No, kept for the record
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  2. Vendor statement

    at disclosure

    CVE-2025-39964 record (CNA: Linux)CuratedQuote verified

    "datePublished":"2025-10-13T13:48:30.334Z"

    Recorded time
    Precision
    To the minute
    Origin
    Curated. Found by a researcher, with a verbatim quote and link.
    Quote check
    Found in the archived copy
    Snapshot
    sha256:e1feb905eee8dd63…
    Used in metrics
    Yes
    Dispute this timestamp

  3. First workaround

    No official mitigation found yet.

  4. First fix

    at disclosure

    kernel.org ChangeLog-6.1.154CuratedQuote verified

    Date: Thu Sep 25 10:58:55 2025 +0200

    Top entry of the Linux 6.1.154 ChangeLog is the release commit 'Linux 6.1.154' dated Thu Sep 25 10:58:55 2025 +0200 = 2025-09-25 08:58 UTC (commit author date). First fixed releases per the CVE record (6.1.154, 6.6.108, 6.12.49, 6.16.9 tagged within minutes of each other on 2025-09-25).

    Source
    kernel.org ChangeLog-6.1.154 vendor github
    Recorded time
    Precision
    To the minute
    Origin
    Curated. Found by a researcher, with a verbatim quote and link.
    Quote check
    Found in the archived copy
    Snapshot
    sha256:0248d215ce7db8cb…
    Used in metrics
    Yes
    Dispute this timestamp

  5. Fixed for all versions

    No evidence yet of fixed releases for every supported branch.

Send this to your boss

No brief for this incident yet. We write one for every open incident and every critical bug exploited before a fix.

Affected products

  • Linux kernel 2.6.38 up to 5.10.244, 5.15.193, 6.1.153, 6.6.107, 6.12.48, 6.16.8 (crypto: af_alg)
How we built this timeline

Kernel moment model: vendor/world = the kernel CNA's CVE publication (first security-labelled public signal); First fix = first stable or mainline release containing the fix (R2: counts even though it precedes the CVE);

Fixed for all versions = the last of the stable/LTS releases the CVE record lists as fixed (R6: provided every then-supported affected line is listed). Release dates come from kernel.org ChangeLog files.

The fix is normally public in stable releases before the CVE is published, so exposure is zero. Downstream lag (Android, distributions) is not graded here.

No public report of exploitation before the fixes; CISA added it to KEV on 18 Sep 2026 together with CVE-2025-39682 and CVE-2026-53266 without a published campaign (The Hacker News: no details on how they are exploited), so the three are separate incidents.

CVSS 7.8 from the kernel CNA record. Correction pass 23 Oct 2026 (R6): Fixed for all versions removed.

The fixed-versions list covers 5.10, 5.15, 6.1, 6.6, 6.12, 6.16 and 6.17 (last listed fix 5.15.194, 2 Oct 2025) but not 5.4, a supported longterm line until its end of life in December 2025, so 'all supported lines fixed' was never reached while 5.4 was supported. Status stays 'patched' because every line supported on 22 Oct 2026 is fixed.

Related

No related incidents.

Linux kernel report card