Linux Kernel up to 7.0.12 rseq rseq_entry.h rseq_exit_user_update uninitialized pointer

Summaryinfo

A vulnerability, which was classified as critical, has been found in Linux Kernel up to 7.0.12. Affected is the function rseq_exit_user_update of the file include/linux/rseq_entry.h of the component rseq. This manipulation causes uninitialized pointer. This vulnerability is handled as CVE-2026-53243. There is not any exploit available. It is advisable to upgrade the affected component.

Detailsinfo

A vulnerability has been found in Linux Kernel up to 7.0.12 and classified as critical. Affected by this vulnerability is the function rseq_exit_user_update of the file include/linux/rseq_entry.h of the component rseq. The manipulation with an unknown input leads to a uninitialized pointer vulnerability. The CWE definition for the vulnerability is CWE-824. The product accesses or uses a pointer that has not been initialized. The impact remains unknown. The summary by CVE is:

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.

The advisory is shared at git.kernel.org. This vulnerability is known as CVE-2026-53243 since 06/09/2026. The exploitation appears to be easy. Technical details are known, but no exploit is available. The price for an exploit might be around USD $0-$5k at the moment (estimation calculated on 06/25/2026).

Upgrading to version 7.0.13 eliminates this vulnerability. Applying the patch e12d20a63b61aaf9de4772effccf42cc9a003e58/6d99479799c69c3cb588fcda19c81d8f61d64ecd is able to eliminate this problem. The bugfix is ready for download at git.kernel.org. The best possible mitigation is suggested to be upgrading to the latest version.

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Productinfo

Type

• Operating System

Vendor

• Linux

Name

• Kernel

Version

• 7.0.0
• 7.0.1
• 7.0.2
• 7.0.3
• 7.0.4
• 7.0.5
• 7.0.6
• 7.0.7
• 7.0.8
• 7.0.9
• 7.0.10
• 7.0.11
• 7.0.12

License

• open-source

Website

• Vendor: https://www.kernel.org/

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