CVE-2025-39931 | crypto: af_alg - Set merge to zero early in af_alg_sendmsg

In the Linux kernel, the following vulnerability has been resolved: crypto: af_alg - Set merge to zero early in af_alg_sendmsg If an error causes af_alg_sendmsg to abort, ctx->merge may contain a garbage value from the previous loop. This may then trigger a crash on the next entry into af_alg_sendmsg when it attempts to do a merge that can't be done. Fix this by setting ctx->merge to zero near the start of the loop.

Published: 2025-10-04 Last update: 2026-06-17 Assigner: 416baaa9-dc9f-4396-8d5f-8c081fb06d67 Source: 416baaa9-dc9f-4396-8d5f-8c081fb06d67
NVD Status：Modified，CVE State: published
View at NVD, CVE.org, EUVD

CVE-2025-39931 is rated Low Risk (23.2/100): CVSS Medium severity, with low exploitation likelihood (EPSS 0.13%). Monitor for updates and reassess as exploit intelligence or EPSS changes.

Risk is dynamic; we continuously reassess and refresh what is shown on this page as upstream context changes.

Exploit prediction scoring system (EPSS) score for CVE-2025-39931

EPSS lead: Daily EPSS estimates relative likelihood of exploitation; percentile ranks this CVE among scored vulnerabilities (higher = more severe relative rank).

# Date Old EPSS score New EPSS score Delta (New - Old)
1 2026-06-15 0.02% 0.13% +0.12%
2 2025-10-04 — 0.02% —

Full EPSS history (2 records total)

Common vulnerability scoring system (CVSS) metrics for CVE-2025-39931

CVSS metrics for this CVE.

Base score Version Severity Vector Exploitability Impact Score source
5.5 3.1 MEDIUM
CVSS:3.1/AV:L/AC:L/PR:L/UI:N/S:U/C:N/I:N/A:H Click to expand
Attack vector (AV:L)
They already need access on the box, or another person has to do something wrong; it’s not a remote drive-by.
Attack complexity (AC:L)
Once they can reach the bug, pulling it off is straightforward—no weird race conditions or rare setup.
Privileges required (PR:L)
A normal user session is enough; they don’t have to be admin.
User interaction (UI:N)
Nobody has to click “OK” or open a trap file; it can work without a victim helping.
Scope (S:U)
Damage stays in the same “trust bubble” as the broken component—no big spill into unrelated systems.
Confidentiality (C:N)
Doesn’t really leak secrets in a meaningful way.
Integrity (I:N)
Data isn’t meaningfully altered or forged.
Availability (A:H)
Could take the service down hard or make it unusable for people who depend on it.
 1.8 3.6 [email protected]

Weakness enumeration for CVE-2025-39931

GitHub Security Advisory for CVE-2025-39931

GHSA-rfcq-q5wv-mpcg · Severity: medium — In the Linux kernel, the following vulnerability has been resolved: crypto: af_alg - Set merge...

OS Trackers for CVE-2025-39931

vendor priority summary link
debian not yet assigned CVE-2025-39931 not yet assigned priority: Debian including 2 source packages (linux, linux-6.1), 6 status rows across 5 suites (bookworm, bullseye, forky, sid, trixie): resolved 5, open 1. https://security-tracker.debian.org/tracker/CVE-2025-39931
redhat medium — https://access.redhat.com/security/cve/CVE-2025-39931
suse medium CVE-2025-39931 severity moderate: SUSE including 467 source package names (2.1.3-6.88:kernel-default-base-6.4.0-36.1.21.13, 2.1.3-7.105:kernel-rt-6.4.0-38.1, …), 948 product×package rows across 195 product lines (Container suse/sl-micro/6.0/base-os-container, Container suse/sl-micro/6.0/kvm-os-container, … (195 product lines)): Fixed 696, Known Affected 231, First Fixed 21. https://www.suse.com/security/cve/CVE-2025-39931/
ubuntu medium CVE-2025-39931 medium priority: Ubuntu including 158 source packages (linux, linux-allwinner-5.19, …), 1414 status rows across 9 suites (bionic, focal, jammy, noble, plucky, questing, trusty, upstream, xenial): DNE 1017, ignored 180, released 117, needed 79, not-affected 17, needs-triage 2, pending 2. https://ubuntu.com/security/CVE-2025-39931

Affected software / configurations for CVE-2025-39931

Vendor Product Version Raw CPE
linux linux_kernel >= 2.6.38, < 6.1.154 cpe:2.3:o:linux:linux_kernel:*:*:*:*:*:*:*:*
linux linux_kernel >= 6.2, < 6.6.108 cpe:2.3:o:linux:linux_kernel:*:*:*:*:*:*:*:*
linux linux_kernel >= 6.7, < 6.12.49 cpe:2.3:o:linux:linux_kernel:*:*:*:*:*:*:*:*
linux linux_kernel >= 6.13, < 6.16.9 cpe:2.3:o:linux:linux_kernel:*:*:*:*:*:*:*:*
linux linux_kernel 6.17 cpe:2.3:o:linux:linux_kernel:6.17:rc1:*:*:*:*:*:*
linux linux_kernel 6.17 cpe:2.3:o:linux:linux_kernel:6.17:rc2:*:*:*:*:*:*
linux linux_kernel 6.17 cpe:2.3:o:linux:linux_kernel:6.17:rc3:*:*:*:*:*:*
linux linux_kernel 6.17 cpe:2.3:o:linux:linux_kernel:6.17:rc4:*:*:*:*:*:*
linux linux_kernel 6.17 cpe:2.3:o:linux:linux_kernel:6.17:rc5:*:*:*:*:*:*
linux linux_kernel 6.17 cpe:2.3:o:linux:linux_kernel:6.17:rc6:*:*:*:*:*:*

References for CVE-2025-39931

cvelogic Threat Intelligence