A vulnerability in the Linux kernel's rseq subsystem involves the use of an uninitialized stack variable in the function rseq_exit_user_update(). (CVE-2026-53243)
A vulnerability in the Linux kernel's rseq subsystem involves the use of an uninitialized stack variable in the function rseq_exit_user_update(). This occurs due to the indeterminate evaluation order of expressions in a structure initializer, causing the node_id field to be set before cpu_id is initialized. The issue was identified by syzbot and results in a kernel information leak detected by KMSAN. The vulnerability has been fixed by moving the assignment of the node_id field outside the structure initialization.
AI Analysis
Technical Summary
The Linux kernel contained a bug in the rseq_exit_user_update() function where an uninitialized stack variable was used due to the indeterminate order of evaluation in a structure initializer. Specifically, the field ids.node_id was assigned using ids.cpu_id before ids.cpu_id was initialized, leading to a kernel information leak detected by KMSAN. The fix involved reordering the assignment to ensure that ids.cpu_id is initialized before ids.node_id is set. This vulnerability is tracked as CVE-2026-53243 and classified under CWE-908 (Use of Uninitialized Variable).
Potential Impact
This vulnerability causes a kernel information leak, which may affect system stability or security by exposing kernel memory contents. The CVSS vector indicates local attack vector with low complexity and low privileges required, no user interaction, unchanged scope, no confidentiality or integrity impact, but high impact on availability. There are no known exploits in the wild.
Mitigation Recommendations
A fix has been implemented in the Linux kernel source code by changing the initialization order of the rseq_ids structure fields. Users should apply the official Linux kernel updates that include this fix once available. Patch status is not yet confirmed in the provided data; check the vendor advisory for current remediation guidance.
A vulnerability in the Linux kernel's rseq subsystem involves the use of an uninitialized stack variable in the function rseq_exit_user_update(). (CVE-2026-53243)
Description
A vulnerability in the Linux kernel's rseq subsystem involves the use of an uninitialized stack variable in the function rseq_exit_user_update(). This occurs due to the indeterminate evaluation order of expressions in a structure initializer, causing the node_id field to be set before cpu_id is initialized. The issue was identified by syzbot and results in a kernel information leak detected by KMSAN. The vulnerability has been fixed by moving the assignment of the node_id field outside the structure initialization.
CVSS v3.1
Score 5.5medium
Weaknesses
AI-Powered Analysis
Machine-generated threat intelligence
Technical Analysis
The Linux kernel contained a bug in the rseq_exit_user_update() function where an uninitialized stack variable was used due to the indeterminate order of evaluation in a structure initializer. Specifically, the field ids.node_id was assigned using ids.cpu_id before ids.cpu_id was initialized, leading to a kernel information leak detected by KMSAN. The fix involved reordering the assignment to ensure that ids.cpu_id is initialized before ids.node_id is set. This vulnerability is tracked as CVE-2026-53243 and classified under CWE-908 (Use of Uninitialized Variable).
Potential Impact
This vulnerability causes a kernel information leak, which may affect system stability or security by exposing kernel memory contents. The CVSS vector indicates local attack vector with low complexity and low privileges required, no user interaction, unchanged scope, no confidentiality or integrity impact, but high impact on availability. There are no known exploits in the wild.
Mitigation Recommendations
A fix has been implemented in the Linux kernel source code by changing the initialization order of the rseq_ids structure fields. Users should apply the official Linux kernel updates that include this fix once available. Patch status is not yet confirmed in the provided data; check the vendor advisory for current remediation guidance.
Technical Details
- Gcve Source
- db.gcve.eu
- Osv Id
- GHSA-qhcg-6255-c538
- Osv Schema Version
- 1.4.0
- Aliases
- ["CVE-2026-53243"]
- Ecosystems
- []
- Database Specific Severity
- MODERATE
- Cvss Version
- 3.1
Threat ID: 6a4e4ee2c9d9e3dbe328955b
Added to database: 07/08/2026, 13:21:38 UTC
Last enriched: 07/08/2026, 13:37:16 UTC
Last updated: 07/31/2026, 19:24:49 UTC
Views: 7
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