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ExploitedIn CISA KEVFix available

CVE-2025-39964

Exploitation confirmed. First attested on 2026-09-18 by CISA-ADP, CISA KEV, GCVE · previdian.

  • Published2025-10-13
  • Fixed in6.16.9 · 6.12.49 · 6.6.108 · 6.1.154 · 5.15.194 · 5.10.245
  • WeaknessCWE-362

Am I affected?

With a domain, we read the version its public headers and pages expose. A distribution build can carry the fix under an older number.

Description

In the Linux kernel, the following vulnerability has been resolved: crypto: af_alg - Disallow concurrent writes in af_alg_sendmsg Issuing two writes to the same af_alg socket is bogus as the data will be interleaved in an unpredictable fashion. Furthermore, concurrent writes may create inconsistencies in the internal socket state. Disallow this by adding a new ctx->write field that indiciates exclusive ownership for writing.

Timeline

dates in UTC
  1. 2025-10-1314:15CVE publishedNVD
  2. 2026-09-18Added to the CISA KEV catalogCISA KEV
  3. 2026-09-18Listed as exploited by GCVEGCVE
  4. 2026-09-18Exploitation first reportedCISA KEV
  5. 2026-09-1814:40SSVC exploitation set to activeCISA-ADP

Observed activity

isMalicious corpus · updated 2026-11-03 21:37 UTC
Indicators tagged with this CVE, per day0 indicators over 7 days
Block these indicators
  • Firewall list (EDL, text): https://api.ismalicious.com/edl/cve/CVE-2025-39964?format=txt
  • CSV export: https://api.ismalicious.com/edl/cve/CVE-2025-39964?format=csv
  • TAXII collection of exploited CVEs
  • The EDL and CSV take an API key on the Pro plan.

Versions per branch

NVD · OSV
Linux linux kernel
BranchAffectedFixed in
6.x≥ 6.13, < 6.16.96.16.9
6.x≥ 6.13.0, < 6.16.96.16.9
6.x≥ 6.7, < 6.12.496.12.49
6.x≥ 6.7.0, < 6.12.496.12.49
6.x≥ 6.2, < 6.6.1086.6.108
6.x≥ 6.2.0, < 6.6.1086.6.108
6.1≥ 5.16, < 6.1.1546.1.154
6.1≥ 5.16.0, < 6.1.1546.1.154
5.x≥ 5.11, < 5.15.1945.15.194
5.x≥ 5.11.0, < 5.15.1945.15.194
5.10≥ 2.6.38, < 5.10.2455.10.245
6.17= 6.17no fix published
Siemens simatic s7-1500 cpu 1518-4 pn\/dp mfp firmwareversion to verify
BranchAffectedFixed in
3.1+≥ 3.1.6no fix published
Siemens simatic s7-1500 cpu 1518f-4 pn\/dp mfp firmwareversion to verify
BranchAffectedFixed in
3.1+≥ 3.1.6no fix published

as publishedRanges as NVD and OSV publish them; a distribution’s build can be fixed under an older number.

Products declared by the CNA2 products

As Linux, the CNA that assigned this CVE, declared them in the CVE record; versions as written.

  • Linuxother versions: not affected

    https://git.kernel.org/pub/scm/linux/kernel/git/stable/linux.git

    Affected
    • ≥ 8ff590903d5fc7f5a0a988c38267a3d08e6393a2, < 0f28c4adbc4a97437874c9b669fd7958a8c6d6cefixed in 0f28c4adbc4a97437874c9b669fd7958a8c6d6cegit
    • ≥ 8ff590903d5fc7f5a0a988c38267a3d08e6393a2, < e4c1ec11132ec466f7362a95f36a506ce4dc08c9fixed in e4c1ec11132ec466f7362a95f36a506ce4dc08c9git
    • ≥ 8ff590903d5fc7f5a0a988c38267a3d08e6393a2, < 1f323a48e9b5ebfe6dc7d130fdf5c3c0e92a07c8fixed in 1f323a48e9b5ebfe6dc7d130fdf5c3c0e92a07c8git
    • ≥ 8ff590903d5fc7f5a0a988c38267a3d08e6393a2, < 7c4491b5644e3a3708f3dbd7591be0a570135b84fixed in 7c4491b5644e3a3708f3dbd7591be0a570135b84git
    • ≥ 8ff590903d5fc7f5a0a988c38267a3d08e6393a2, < 9aee87da5572b3a14075f501752e209801160d3dfixed in 9aee87da5572b3a14075f501752e209801160d3dgit
    • ≥ 8ff590903d5fc7f5a0a988c38267a3d08e6393a2, < 45bcf60fe49b37daab1acee57b27211ad1574042fixed in 45bcf60fe49b37daab1acee57b27211ad1574042git
    • ≥ 8ff590903d5fc7f5a0a988c38267a3d08e6393a2, < 1b34cbbf4f011a121ef7b2d7d6e6920a036d5285fixed in 1b34cbbf4f011a121ef7b2d7d6e6920a036d5285git
  • Linuxother versions: affected

    https://git.kernel.org/pub/scm/linux/kernel/git/stable/linux.git

    Affected
    • = 2.6.38no fix stated

    Not affected < 2.6.38 · ≥ 5.10.245, ≤ 5.10.* · ≥ 5.15.194, ≤ 5.15.* · ≥ 6.1.154, ≤ 6.1.* · ≥ 6.6.108, ≤ 6.6.* · ≥ 6.12.49, ≤ 6.12.* · ≥ 6.16.9, ≤ 6.16.*

    1 more version line in the CVE record.

Source: the CNA record (CVE Program), © The MITRE Corporation,CVE Terms of UseCVE recordupdated 2026-08-05

Distribution builds and vendor advisories

Packages from OSV.dev and products from the vendors' CSAF advisories.

version not verifiedVersions not verified: read as OSV.dev and the vendors publish them, not checked against each vendor's release list.

Packages

  • bpftoolTuxCare:AlmaLinux:9.2all versions · fixed in 7.0.0-284.1101.el9_2.tuxcare.11.els15
  • dtb-aarch64openSUSE:Leap 15.6all versions · fixed in 6.4.0-150600.23.92.1and 10 other packages
  • kernelTuxCare:RHEL:7all versions · fixed in 3.10.0-1160.164.1.el7.tuxcare.els1and 11 other packages
  • kernelTuxCare:OracleLinux:7all versions · fixed in 3.10.0-1160.164.1.el7.tuxcare.els1and 11 other packages
  • kernelTuxCare:CentOS:8.5all versions · fixed in 4.18.0-348.7.1.el8_5.tuxcare.els48and 21 other packages
  • kernelTuxCare:CentOS:8.4all versions · fixed in 4.18.0-305.25.1.el8_4.tuxcare.els48and 21 other packages
  • kernelTuxCare:CentOS:7all versions · fixed in 3.10.0-1160.164.1.el7.tuxcare.els1and 11 other packages
  • kernelTuxCare:CentOS-Stream:8all versions · fixed in 4.18.0-553.6.1.el8_10.tuxcare.els31and 21 other packages

135 more package ranges on OSV.dev

Vendor advisories

  • CVE-2025-39964 Red Hat Product Security2,333 products fixed

    kernel: crypto: af_alg - Disallow concurrent writes in af_alg_sendmsg

  • ICSA-26-295-11 CISA5 known affected

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

    SIMATIC S7-1500 CPU 1518-4 PN/DP MFP (6ES7518-4AX00-1AB0) >= V3.1.7 · SIMATIC S7-1500 CPU 1518-4 PN/DP MFP (6ES7518-4AX00-1AC0) >= V3.1.7 · SIMATIC S7-1500 CPU 1518F-4 PN/DP MFP (6ES7518-4FX00-1AB0) >= V3.1.7 · +2 more

  • SSA-457936 Siemens ProductCERT5 known affected

    SSA-457936: Vulnerabilities in the additional GNU/Linux subsystem of the SIMATIC S7-1500 CPU 1518(F)-4 PN/DP MFP V3.1.7

    SIMATIC S7-1500 CPU 1518-4 PN/DP MFP (6ES7518-4AX00-1AB0) >= V3.1.7 · SIMATIC S7-1500 CPU 1518-4 PN/DP MFP (6ES7518-4AX00-1AC0) >= V3.1.7 · SIMATIC S7-1500 CPU 1518F-4 PN/DP MFP (6ES7518-4FX00-1AB0) >= V3.1.7 · +2 more

  • RHSA-2026:73788 Red Hat Product Security53 products fixed

    Red Hat Security Advisory: kernel security, bug fix, and enhancement update

  • RHSA-2026:72059 Red Hat Product Security53 products fixed

    Red Hat Security Advisory: kernel security update

  • RHSA-2026:71687 Red Hat Product Security93 products fixed

    Red Hat Security Advisory: kernel security update

15 more advisories

Full record on NVD

Fix

  1. Update Linux linux kernel to 6.16.9 · 6.12.49 · 6.6.108 · 6.1.154 · 5.15.194 · 5.10.245
  2. CISA’s required action: Apply mitigations in accordance with vendor instructions, ensuring compliance with CISA’s BOD 26-04 Prioritizing Security Updates Based on Risk (see URL in Notes) guidance and CISA’s “Forensics Triage Requirements” (see URL in Notes). Follow applicable BOD 26-04 guidance for cloud services or discontinue use of the product if mitigations are unavailable. Stakeholders are responsible for evaluating each asset's internet exposure and ensuring adherence to BOD 26-04 patching guidelines.due 2026-09-21
  3. Vendor fix Red Hat Product Security RHSA-2026:73788 · 53 productsBefore applying this update, make sure all previously released errata relevant to your system have been applied. For details on how to apply this update, refer to: https://access.redhat.com/articles/11258
  4. Vendor fix Red Hat Product Security RHSA-2026:72059 · 53 productsFor details on how to apply this update, which includes the changes described in this advisory, refer to: https://access.redhat.com/articles/11258 The system must be rebooted for this update to take effect. Red Hat recommends treating all kernel errata as security-relevant. Given the kernel's fu…
  5. Workaround from the vendor Red Hat Product Security RHSA-2026:73788 · 53 productsMitigation for this issue is either not available or the currently available options do not meet the Red Hat Product Security criteria comprising ease of use and deployment, applicability to widespread installation base, or stability.
  6. Mitigation from the vendor Siemens ProductCERT SSA-457936 · 5 productsLimit access to the interactive shell of the additional GNU/Linux subssytem to trusted personnel only.
  7. Mitigation from the vendor Siemens ProductCERT SSA-457936 · 5 productsOnly build and run applications from trusted sources.
  8. Mitigation from the vendor CISA ICSA-26-295-11 · 5 productsLimit access to the interactive shell of the additional GNU/Linux subssytem to trusted personnel only.

Advisories and patches

Detection

read 2026-11-02 22:42 UTC
Nuclei template
none so far
ProjectDiscovery
Exploit-DB
no entry
Exploit-DB
Proof-of-concept repositories
2 repositories, unverifiedn1k0oowang/CVE-2025-39964_EXPsuominen/CVE-2025-39964
PoC-in-GitHub
Metasploit modules
none listed
Metasploit Framework

CISA Known Exploited Vulnerability

Date Added
2026-09-18
Patch Due Date
2026-09-21
Ransomware Use
Unknown
Required Action
Apply mitigations in accordance with vendor instructions, ensuring compliance with CISA’s BOD 26-04 Prioritizing Security Updates Based on Risk (see URL in Notes) guidance and CISA’s “Forensics Triage Requirements” (see URL in Notes). Follow applicable BOD 26-04 guidance for cloud services or discontinue use of the product if mitigations are unavailable. Stakeholders are responsible for evaluating each asset's internet exposure and ensuring adherence to BOD 26-04 patching guidelines.

Sources

Identifiers

Technical details

CVSS v3 Vector
CVSS:3.1/AV:L/AC:L/PR:L/UI:N/S:U/C:N/I:N/A:H
Published
2025-10-13
Last Modified
2026-10-19
NVD status
Analyzed
GitHub Advisory
GHSA-wr5g-mfhw-rpfj

Frequently asked questions

What is CVE-2025-39964?

In the Linux kernel, the following vulnerability has been resolved: crypto: af_alg - Disallow concurrent writes in af_alg_sendmsg Issuing two writes to the same af_alg socket is bogus as the data will be interleaved in an unpredictable fashion. Furthermore, concurrent writes may create inconsistencies in the internal socket state. Disallow this by adding a new ctx->write field that indiciates exclusive ownership for writing.

Is CVE-2025-39964 actively exploited?

Yes. CVE-2025-39964 is on the CISA Known Exploited Vulnerabilities (KEV) catalog, meaning it has been confirmed as actively exploited in the wild. CISA requires federal agencies to patch by 2026-09-21.

What is the CVSS score for CVE-2025-39964?

CVE-2025-39964 has a CVSS v3 base score of 5.5 (MEDIUM severity), with vector string CVSS:3.1/AV:L/AC:L/PR:L/UI:N/S:U/C:N/I:N/A:H.

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