--- id: CVE-2025-39964 title: |- 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… summary: |- 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… severity: high cvss: 7.8 cvssVector: 'CVSS:3.1/AV:L/AC:L/PR:L/UI:N/S:U/C:H/I:H/A:H' cwe: - CWE-362 - CWE-366 vendor: linux product: linux_kernel affected: - 'linux_kernel >= 2.6.38, < 5.10.245' - 'linux_kernel >= 5.11, < 5.15.194' - 'linux_kernel >= 5.16, < 6.1.154' - 'linux_kernel >= 6.2, < 6.6.108' - 'linux_kernel >= 6.7, < 6.12.49' - 'linux_kernel >= 6.13, < 6.16.9' - linux_kernel = 6.17 - simatic_s7-1500_cpu_1518-4_pn/dp_mfp_firmware >= 3.1.6 - simatic_s7-1500_cpu_1518f-4_pn/dp_mfp_firmware >= 3.1.6 patched: - linux_kernel 6.16.9 published: '2025-10-13' updated: '2026-09-19' sourceUpdated: '2026-09-19T04:17:48.307' source: NVD sourceUrl: 'https://nvd.nist.gov/vuln/detail/CVE-2025-39964' references: - url: 'https://git.kernel.org/stable/c/0f28c4adbc4a97437874c9b669fd7958a8c6d6ce' label: 416baaa9-dc9f-4396-8d5f-8c081fb06d67 - url: 'https://git.kernel.org/stable/c/1b34cbbf4f011a121ef7b2d7d6e6920a036d5285' label: 416baaa9-dc9f-4396-8d5f-8c081fb06d67 - url: 'https://git.kernel.org/stable/c/1f323a48e9b5ebfe6dc7d130fdf5c3c0e92a07c8' label: 416baaa9-dc9f-4396-8d5f-8c081fb06d67 - url: 'https://git.kernel.org/stable/c/45bcf60fe49b37daab1acee57b27211ad1574042' label: 416baaa9-dc9f-4396-8d5f-8c081fb06d67 - url: 'https://git.kernel.org/stable/c/7c4491b5644e3a3708f3dbd7591be0a570135b84' label: 416baaa9-dc9f-4396-8d5f-8c081fb06d67 - url: 'https://git.kernel.org/stable/c/9aee87da5572b3a14075f501752e209801160d3d' label: 416baaa9-dc9f-4396-8d5f-8c081fb06d67 - url: 'https://git.kernel.org/stable/c/e4c1ec11132ec466f7362a95f36a506ce4dc08c9' label: 416baaa9-dc9f-4396-8d5f-8c081fb06d67 - url: 'https://cert-portal.siemens.com/productcert/html/ssa-019113.html' label: 0b142b55-0307-4c5a-b3c9-f314f3fb7c5e - url: >- https://www.cisa.gov/known-exploited-vulnerabilities-catalog?field_cve=CVE-2025-39964 label: 134c704f-9b21-4f2e-91b3-4a467353bcc0 - url: >- https://security.access.redhat.com/data/csaf/v2/vex/2025/cve-2025-39964.json - url: 'https://access.redhat.com/security/cve/CVE-2025-39964' - url: 'https://bugzilla.redhat.com/show_bug.cgi?id=2403545' - url: 'https://www.cve.org/CVERecord?id=CVE-2025-39964' - url: 'https://nvd.nist.gov/vuln/detail/CVE-2025-39964' - url: >- https://lore.kernel.org/linux-cve-announce/2025101334-CVE-2025-39964-7964@gregkh/T - url: 'https://www.cisa.gov/known-exploited-vulnerabilities-catalog' - url: 'https://access.redhat.com/errata/RHSA-2026:70402' - url: 'https://access.redhat.com/errata/RHSA-2026:70403' - url: 'https://access.redhat.com/errata/RHSA-2026:70498' - url: 'https://access.redhat.com/errata/RHSA-2026:71327' - url: 'https://access.redhat.com/errata/RHSA-2026:70459' - url: 'https://access.redhat.com/errata/RHSA-2026:71687' - url: 'https://access.redhat.com/errata/RHSA-2026:71657' - url: 'https://access.redhat.com/errata/RHSA-2026:71326' - url: 'https://access.redhat.com/errata/RHSA-2026:71601' - url: 'https://access.redhat.com/errata/RHSA-2026:71569' - url: 'https://access.redhat.com/errata/RHSA-2026:71565' - url: 'https://access.redhat.com/errata/RHSA-2026:71592' - url: 'https://access.redhat.com/errata/RHSA-2026:71594' - url: 'https://access.redhat.com/errata/RHSA-2026:71606' - url: 'https://access.redhat.com/errata/RHSA-2026:72059' tags: - nvd - cve.org - in-the-wild - exploit-available - kev - csaf - vex - red-hat exploited: true exploitAvailable: true ssvc: exploitation: active automatable: 'no' technicalImpact: total timestamp: '2026-09-18T14:40:05.718549Z' epss: 0.00996 epssPercentile: 0.61122 kev: true kevDateAdded: '2026-09-18' kevDueDate: '2026-09-21' kevRansomware: false exploits: github: 3 githubRepos: - 'https://github.com/n1k0oowang/CVE-2025-39964_EXP' - 'https://github.com/suominen/CVE-2025-39964' - >- https://github.com/mc493/linux-kernel-zero-day-mitigation-zero-downtime-kernel-defense- checkedAt: '2026-09-26T09:05:33.471Z' ingestedAt: '2026-09-08T15:33:26.996Z' scores: nvd: 7.8 vendor: 7.3 --- ## Overview 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. ## Affected - `linux_kernel >= 2.6.38, < 5.10.245` - `linux_kernel >= 5.11, < 5.15.194` - `linux_kernel >= 5.16, < 6.1.154` - `linux_kernel >= 6.2, < 6.6.108` - `linux_kernel >= 6.7, < 6.12.49` - `linux_kernel >= 6.13, < 6.16.9` - `linux_kernel = 6.17` - `simatic_s7-1500_cpu_1518-4_pn/dp_mfp_firmware >= 3.1.6` - `simatic_s7-1500_cpu_1518f-4_pn/dp_mfp_firmware >= 3.1.6` ## Remediation Upgrade past the affected range: - `linux_kernel 6.16.9` ## Vendor advisories - **Red Hat VEX** · Moderate · affected: Red Hat Enterprise Linux 9, Red Hat Enterprise Linux for NVIDIA 26 · no fix planned: Red Hat Enterprise Linux 9, Red Hat Enterprise Linux for NVIDIA 26 · updated 2026-09-25 · [vex](https://security.access.redhat.com/data/csaf/v2/vex/2025/cve-2025-39964.json) - **RHSA-2026:70402** · Red Hat · fixed in: Red Hat Enterprise Linux BaseOS (v. 8), Red Hat Enterprise Linux CRB (v. 8) · released 2026-09-22 · [advisory](https://access.redhat.com/errata/RHSA-2026:70402) - **RHSA-2026:70403** · Red Hat · fixed in: Red Hat Enterprise Linux NFV (v. 8), Red Hat Enterprise Linux RT (v. 8) · released 2026-09-22 · [advisory](https://access.redhat.com/errata/RHSA-2026:70403) - **RHSA-2026:70498** · Red Hat · fixed in: Red Hat Enterprise Linux AppStream (v. 10), Red Hat Enterprise Linux BaseOS (v. 10), Red Hat Enterprise Linux CodeReady Linux Builder (v. 10), Red Hat Enterprise Linux Real Time for NFV (v. 10), Red Hat Enterprise Linux Real Time (v. 10) · released 2026-09-23 · [advisory](https://access.redhat.com/errata/RHSA-2026:70498) - **RHSA-2026:71327** · Red Hat · fixed in: Red Hat Enterprise Linux AppStream EUS (v.9.6), Red Hat Enterprise Linux BaseOS EUS (v.9.6), Red Hat CodeReady Linux Builder EUS (v.9.6), Red Hat Enterprise Linux Real Time for NFV EUS (v.9.6), Red Hat Enterprise Linux Real Time EUS (v.9.6) · released 2026-09-24 · [advisory](https://access.redhat.com/errata/RHSA-2026:71327) - **RHSA-2026:70459** · Red Hat · fixed in: Red Hat Enterprise Linux AppStream (v. 9), Red Hat Enterprise Linux BaseOS (v. 9), Red Hat Enterprise Linux CodeReady Linux Builder (v. 9), Red Hat Enterprise Linux Real Time for NFV (v. 9), Red Hat Enterprise Linux Real Time (v. 9) · released 2026-09-23 · [advisory](https://access.redhat.com/errata/RHSA-2026:70459) - **RHSA-2026:71687** · Red Hat · fixed in: Red Hat Enterprise Linux Server (v. 7 ELS), Red Hat Enterprise Linux Server Optional (v. 7 ELS) · released 2026-09-24 · [advisory](https://access.redhat.com/errata/RHSA-2026:71687) - **RHSA-2026:71657** · Red Hat · fixed in: Red Hat Enterprise Linux for Real Time (v. 7 ELS) · released 2026-09-24 · [advisory](https://access.redhat.com/errata/RHSA-2026:71657) - **RHSA-2026:71326** · Red Hat · fixed in: Red Hat Enterprise Linux AppStream EUS (v. 10.0), Red Hat Enterprise Linux BaseOS EUS (v. 10.0), Red Hat Enterprise Linux CodeReady Linux Builder EUS (v. 10.0), Red Hat Enterprise Linux Real Time for NFV EUS (v. 10.0), Red Hat Enterprise Linux Real Time EUS (v. 10.0) · released 2026-09-24 · [advisory](https://access.redhat.com/errata/RHSA-2026:71326) - **RHSA-2026:71601** · Red Hat · fixed in: Red Hat Enterprise Linux AppStream E4S (v.9.2), Red Hat Enterprise Linux BaseOS E4S (v.9.2) · released 2026-09-24 · [advisory](https://access.redhat.com/errata/RHSA-2026:71601) - **RHSA-2026:71569** · Red Hat · fixed in: Red Hat Enterprise Linux AppStream E4S (v.9.4), Red Hat Enterprise Linux BaseOS E4S (v.9.4), Red Hat Enterprise Linux Real Time for NFV E4S (v.9.4), Red Hat Enterprise Linux Real Time E4S (v.9.4) · released 2026-09-24 · [advisory](https://access.redhat.com/errata/RHSA-2026:71569) - **RHSA-2026:71565** · Red Hat · fixed in: Red Hat Enterprise Linux BaseOS AUS (v.8.4), Red Hat Enterprise Linux BaseOS EUS EXTENSION (v.8.4) · released 2026-09-24 · [advisory](https://access.redhat.com/errata/RHSA-2026:71565) - **RHSA-2026:71592** · Red Hat · fixed in: Red Hat Enterprise Linux BaseOS AUS (v.8.6), Red Hat Enterprise Linux BaseOS EUS EXTENSION (v.8.6) · released 2026-09-24 · [advisory](https://access.redhat.com/errata/RHSA-2026:71592) - **RHSA-2026:72059** · Red Hat · fixed in: NVIDIA for RHEL 10 · released 2026-09-25 · [advisory](https://access.redhat.com/errata/RHSA-2026:72059)