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

Summary

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.

Timeline

1. Aug 4, 2026, 6:23 AM UTCCVE published73 days
2. Oct 16, 2026, 3:42 PM UTCCISA SSVC assessment

   Exploitation: none · Automatable: yes · Technical impact: total

   3 days
3. Oct 19, 2026, 8:48 PM UTCRecord last updated

Affected versions

• Linux 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 Linux

  2.6.25

• KernelLinux

  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

References 9