What’s Vulnerable › Vulnerabilities

CVE-2025-21836: io_uring/kbuf: reallocate buf lists on upgrade

• Severity: medium (CVSS 5.5 v3.1)
• Exploited in the wild: not listed in CISA KEV
• EPSS: 0.3% probability of exploitation in the next 30 days
• Public exploit or detection template: none known
• Published: 2025-03-07 · updated 2026-10-15

Description

In the Linux kernel, the following vulnerability has been resolved: io_uring/kbuf: reallocate buf lists on upgrade IORING_REGISTER_PBUF_RING can reuse an old struct io_buffer_list if it was created for legacy selected buffer and has been emptied. It violates the requirement that most of the field should stay stable after publish. Always reallocate it instead.

Affected products

• Linux kernel: from 5.19 before 6.6.79; from 6.7 before 6.12.16; from 6.13 before 6.13.4; 6.14-rc1, 6.14-rc2 — fixed in 6.12.16, 6.13.4, 6.6.79

How to fix

Upgrade to a fixed version: Linux kernel 6.12.16, 6.13.4, 6.6.79. Check the vendor advisory for mitigations.

References

• https://git.kernel.org/stable/c/146a185f6c05ee263db715f860620606303c4633
• https://git.kernel.org/stable/c/2a5febbef40ce968e295a7aeaa5d5cbd9e3e5ad4
• https://git.kernel.org/stable/c/7d0dc28dae836caf7645fef62a10befc624dd17b
• https://git.kernel.org/stable/c/8802766324e1f5d414a81ac43365c20142e85603
• https://u1f383.github.io/slides/talks/2025_Hexacon-Deja_Vu_in_Linux_io_uring_Breaking_Memory_Sharing_Again_After_Generations_of_Fixes.pdf

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