A vulnerability in the Linux kernel's crypto subsystem (af_alg) could cause a crash due to improper handling of the ctx->merge variable when… (CVE-2025-39931)
A vulnerability in the Linux kernel's crypto subsystem (af_alg) could cause a crash due to improper handling of the ctx->merge variable when af_alg_sendmsg aborts. The issue arises because ctx->merge may retain a garbage value from a previous loop iteration, leading to a crash on subsequent calls. The fix involves setting ctx->merge to zero early in the processing loop to prevent this condition.
AI Analysis
Technical Summary
The vulnerability in the Linux kernel's crypto: af_alg component involves improper initialization of the ctx->merge variable in the af_alg_sendmsg function. If an error causes af_alg_sendmsg to abort, ctx->merge may contain stale data from a previous iteration, which can trigger a crash on the next invocation when an invalid merge operation is attempted. The issue is addressed by initializing ctx->merge to zero near the start of the processing loop, preventing the use of invalid data.
Potential Impact
This vulnerability does not affect confidentiality or integrity but can cause a denial of service through a crash of the kernel crypto subsystem when af_alg_sendmsg is called under error conditions. There are no known exploits in the wild. The impact is limited to availability disruption.
Mitigation Recommendations
Patch status is not yet confirmed — check the vendor advisory for current remediation guidance. Since this is a kernel-level issue, applying official Linux kernel updates that include the fix is recommended once available. Until then, avoid triggering conditions that cause af_alg_sendmsg to abort if possible.
A vulnerability in the Linux kernel's crypto subsystem (af_alg) could cause a crash due to improper handling of the ctx->merge variable when… (CVE-2025-39931)
Description
A vulnerability in the Linux kernel's crypto subsystem (af_alg) could cause a crash due to improper handling of the ctx->merge variable when af_alg_sendmsg aborts. The issue arises because ctx->merge may retain a garbage value from a previous loop iteration, leading to a crash on subsequent calls. The fix involves setting ctx->merge to zero early in the processing loop to prevent this condition.
CVSS v3.1
Score 5.5medium
Weaknesses
AI-Powered Analysis
Machine-generated threat intelligence
Technical Analysis
The vulnerability in the Linux kernel's crypto: af_alg component involves improper initialization of the ctx->merge variable in the af_alg_sendmsg function. If an error causes af_alg_sendmsg to abort, ctx->merge may contain stale data from a previous iteration, which can trigger a crash on the next invocation when an invalid merge operation is attempted. The issue is addressed by initializing ctx->merge to zero near the start of the processing loop, preventing the use of invalid data.
Potential Impact
This vulnerability does not affect confidentiality or integrity but can cause a denial of service through a crash of the kernel crypto subsystem when af_alg_sendmsg is called under error conditions. There are no known exploits in the wild. The impact is limited to availability disruption.
Mitigation Recommendations
Patch status is not yet confirmed — check the vendor advisory for current remediation guidance. Since this is a kernel-level issue, applying official Linux kernel updates that include the fix is recommended once available. Until then, avoid triggering conditions that cause af_alg_sendmsg to abort if possible.
Technical Details
- Gcve Source
- db.gcve.eu
- Osv Id
- GHSA-rfcq-q5wv-mpcg
- Osv Schema Version
- 1.4.0
- Aliases
- ["CVE-2025-39931"]
- Database Specific Severity
- MODERATE
- Cvss Version
- 3.1
Threat ID: 6a498a7827e9c7971936efe1
Added to database: 07/04/2026, 22:34:32 UTC
Last enriched: 07/04/2026, 23:07:19 UTC
Last updated: 09/10/2026, 19:36:50 UTC
Views: 24
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