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CVE-2026-53243

5.5 · MEDIUM

In the Linux kernel, the following vulnerability has been resolved: rseq: Fix using an uninitialized stack variable in rseq_exit_user_update() There is an bug in which an uninitialized stack vari…

Published Jun 25, 2026CWE-908EPSS 0.11%

Overview

CVE-2026-53243 is a medium-severity vulnerability. It was published on June 25, 2026 and has a CVSS 3.1 base score of 5.5 (MEDIUM).

This vulnerability has a CVSS 3.1 base score of 5.5, rated MEDIUM. It requires local or adjacent network access to exploit. Some level of privileges is required for exploitation.

Technical description

In the Linux kernel, the following vulnerability has been resolved:

rseq: Fix using an uninitialized stack variable in rseq_exit_user_update()

There is an bug in which an uninitialized stack variable is used in

rseq_exit_user_update() as reported by syzbot:

BUG: KMSAN: kernel-infoleak in rseq_set_ids_get_csaddr include/linux/rseq_entry.h:502 [inline]

The local variable:

struct rseq_ids ids = {

.cpu_id = task_cpu(t),

.mm_cid = task_mm_cid(t),

.node_id = cpu_to_node(ids.cpu_id),

};

According to the C standard, the evaluation order of expressions in an

initializer list is indeterminately sequenced. The compiler (Clang, in

this KMSAN build) evaluates `cpu_to_node(ids.cpu_id)` *before*

`ids.cpu_id` is initialized with `task_cpu(t)`.

This is fixed by moving the assignment of ids.node_id outside the

structure initialization.

Remediation

Check the references section for vendor advisories, patches, and mitigation guidance. If immediate patching is not possible, review the CVSS vector to understand the attack surface and apply compensating controls such as network segmentation or access restrictions.

References

Refgit.kernel.org/stable/c/6d99479799c69c3cb588fcda19c81d8f61d64ecdRefgit.kernel.org/stable/c/e12d20a63b61aaf9de4772effccf42cc9a003e58

How CyberStrike helps

Frequently asked questions

What is CVE-2026-53243?

CVE-2026-53243 is a medium-severity vulnerability. It was published on June 25, 2026 and has a CVSS 3.1 base score of 5.5 (MEDIUM).

How severe is CVE-2026-53243?

This vulnerability has a CVSS 3.1 base score of 5.5, rated MEDIUM. It requires local or adjacent network access to exploit. Some level of privileges is required for exploitation.

How do I fix or remediate CVE-2026-53243?

Check the references section for vendor advisories, patches, and mitigation guidance. If immediate patching is not possible, review the CVSS vector to understand the attack surface and apply compensating controls such as network segmentation or access restrictions.

How can CyberStrike help with CVE-2026-53243?

CyberStrike is an open-source, AI-augmented pentesting engine. Rather than flag a version number, it tests whether an issue like CVE-2026-53243 is actually reachable in your own applications and APIs, then verifies each finding before reporting it. That tells you if the weakness is a real, exploitable risk in your environment or a false positive you can safely deprioritize.

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