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.
do firstUpgrade to a fixed release: < 2.6.38, >= 5.10.245 and <= 5.10.*, >= 5.15.194 and <= 5.15.*, >= 6.1.154 and <= 6.1.* (+4 more below).
Can a WAF block it? No. The attack needs local access to the machine, so a WAF is not on its path.
Also consider: patch
Based on the attack vector (local or physical access). We check Cloudflare, AWS, Google Cloud Armor and Azure; for Akamai, Imperva, Fastly, F5, ask your vendor.
Is CVE-2025-39964 being exploited?
Yes. CVE-2025-39964 appears in CISA's Known Exploited Vulnerabilities catalog, which means exploitation in the wild has been confirmed and reported. Treat it as active rather than theoretical, and patch it ahead of higher-scoring vulnerabilities that carry no exploitation evidence.
How severe is CVE-2025-39964?
CVE-2025-39964 is rated High with a CVSS score of 7.8. Severity describes how bad exploitation would be, not how likely it is: pair it with exploitation evidence before deciding what to patch first.
Is there a patch for CVE-2025-39964?
Yes. A fix has been recorded for CVE-2025-39964. The vendor advisory is the authority on the exact fixed version — apply it from there rather than from a summary.
What does CVE-2025-39964 affect?
CVE-2025-39964 affects linux:linux_kernel, siemens:simatic_s7-1500_cpu_1518-4_pn\/dp_mfp_firmware, siemens:simatic_s7-1500_cpu_1518f-4_pn\/dp_mfp_firmware. Confirm the exact affected versions against the vendor advisory before deciding you are exposed.
Exploitation status reflects CISA's KEV catalog as we last synced it. Check the catalog directly.
- affected>= 8ff590903d5fc7f5a0a988c38267a3d08e6393a2 and < 0f28c4adbc4a97437874c9b669fd7958a8c6d6ce
- affected>= 8ff590903d5fc7f5a0a988c38267a3d08e6393a2 and < e4c1ec11132ec466f7362a95f36a506ce4dc08c9
- affected>= 8ff590903d5fc7f5a0a988c38267a3d08e6393a2 and < 1f323a48e9b5ebfe6dc7d130fdf5c3c0e92a07c8
- affected>= 8ff590903d5fc7f5a0a988c38267a3d08e6393a2 and < 7c4491b5644e3a3708f3dbd7591be0a570135b84
- affected>= 8ff590903d5fc7f5a0a988c38267a3d08e6393a2 and < 9aee87da5572b3a14075f501752e209801160d3d
- affected>= 8ff590903d5fc7f5a0a988c38267a3d08e6393a2 and < 45bcf60fe49b37daab1acee57b27211ad1574042
- affected>= 8ff590903d5fc7f5a0a988c38267a3d08e6393a2 and < 1b34cbbf4f011a121ef7b2d7d6e6920a036d5285
- affected2.6.38
As published in the CVE Program record. A version outside these ranges is not a statement that it is unaffected — vendors sometimes understate a range, and distribution-backported builds carry upstream numbers that do not reflect what was patched into them.
public exploits
Unvetted proof-of-concept code on GitHub: 2 GitHub proofs of concept
Listed so you can judge urgency, not as a recommendation to run anything. GitHub “proofs of concept” are unvetted: some are fake or carry malware. Exploit-DB marks the entries its staff verified.
cisa ssvc
- exploitation
- active
- automatable
- no
- technical impact
- total
Assessed by CISA 18 Sept 2026 (SSVC 2.0.3).
timeline
- 13 Oct 2025Published
- 13 Nov 2025First proof-of-concept repository on GitHub (unvetted) · 30 days later
- 18 Sept 2026Added to CISA KEV (exploited in the wild) · 309 days (about 10 months) later
- 18 Sept 2026CISA SSVC assessment: exploitation active · same day later
- 21 Sept 2026CISA remediation due date (US federal agencies) · 3 days later
- 15 Oct 2026CVE record last updated · 24 days later
- 2 Nov 2026Analysed by vulneraibility.com · 19 days later
- Linkgit.kernel.org /stable/c/0f28c4adbc4a97437874c9b669fd7958a8c6d6ce
- Linkgit.kernel.org /stable/c/e4c1ec11132ec466f7362a95f36a506ce4dc08c9
- Linkgit.kernel.org /stable/c/1f323a48e9b5ebfe6dc7d130fdf5c3c0e92a07c8
- Linkgit.kernel.org /stable/c/7c4491b5644e3a3708f3dbd7591be0a570135b84
- Linkgit.kernel.org /stable/c/9aee87da5572b3a14075f501752e209801160d3d
- Linkgit.kernel.org /stable/c/45bcf60fe49b37daab1acee57b27211ad1574042
- Linkgit.kernel.org /stable/c/1b34cbbf4f011a121ef7b2d7d6e6920a036d5285
- Linkcisa.gov /known-exploited-vulnerabilities-catalog?field_cve=CVE-2025-39964
Show 2 more
- Linkcert-portal.siemens.com /productcert/html/ssa-019113.html
- Linkcert-portal.siemens.com /productcert/html/ssa-457936.html
sources
- CVE List (CVE.org): description, affected versions, references; CVE Terms of Use
- NVD: CVSS and CPE data
- CISA KEV catalog: exploitation, date added, due date
- CISA Vulnrichment (ADP): SSVC decision points
- FIRST EPSS: exploit probability and percentile
- PoC-in-GitHub: GitHub repositories that claim a proof of concept
- Summary, impact and triage tags: written by our AI analysis pipeline from the sources above. Check them against the sources.