CVE-2026-31693
Published: 30 April 2026
Summary
CVE-2026-31693 is a high-severity Use of Uninitialized Resource (CWE-908) vulnerability in Linux Linux Kernel. Its CVSS base score is 7.8 (High).
Operationally, exploitation aligns with the MITRE ATT&CK technique Exploitation for Privilege Escalation (T1068); ranked at the 2.4th percentile by exploit likelihood (below the median); it is not currently listed in the CISA KEV catalog.
The strongest mitigations our analysis identified are NIST 800-53 RA-5 (Vulnerability Monitoring and Scanning) and SI-2 (Flaw Remediation).
Threat & Defense at a Glance
Threat & Defense Details
Mitigating Controls (NIST 800-53 r5)AI
SI-2 Flaw Remediation directly requires timely patching of the Linux kernel to address the missing variable initializations in CIFS replay code as fixed by specific commits for CVE-2026-31693.
RA-5 Vulnerability Monitoring and Scanning identifies systems with vulnerable Linux kernel versions affected by CVE-2026-31693 through regular scanning.
SI-5 Security Alerts, Advisories, and Directives ensures organizations receive and act on notifications about kernel vulnerabilities like CVE-2026-31693 to facilitate patching.
MITRE ATT&CK Enterprise TechniquesAI
Why these techniques?
Local kernel flaw (uninitialized variables in CIFS replay paths) with CVSS 7.8 AV:L impacts directly enables T1068 Exploitation for Privilege Escalation to obtain kernel-level code execution and full system compromise.
NVD Description
In the Linux kernel, the following vulnerability has been resolved: cifs: some missing initializations on replay In several places in the code, we have a label to signify the start of the code where a request can be replayed if…
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necessary. However, some of these places were missing the necessary reinitializations of certain local variables before replay. This change makes sure that these variables get initialized after the label.
Deeper analysisAI
CVE-2026-31693 is a vulnerability in the Linux kernel's CIFS (Common Internet File System) implementation. The issue stems from missing initializations of certain local variables at replay labels in the code. These labels mark the start of sections where SMB requests can be replayed if necessary, but prior to the fix, some locations failed to reinitialize the variables, potentially leading to incorrect behavior during replays.
The vulnerability has a CVSS v3.1 base score of 7.8 (AV:L/AC:L/PR:L/UI:N/S:U/C:H/I:H/A:H), indicating it can be exploited by a local attacker with low privileges. Exploitation requires low complexity and no user interaction, allowing the attacker to achieve high impacts on confidentiality, integrity, and availability within the affected system.
Mitigation is provided through kernel patches available in the stable repository. Relevant commits include 14f66f44646333d2bfd7ece36585874fd72f8286, 1d731e512134495e0ef490ade0e4d91dc0d515ec, 7c9ce68192eef14c777cb6ce17155d2eb2431aea, c854ab481ece4b3e5f4c2e8b22824f015ff874a5, and c99e160938b627f6f28edee930e8abc157e84386, which ensure proper variable initialization after replay labels. Security practitioners should update to kernels incorporating these fixes.
Details
- CWE(s)