CVE-2026-64564

In the Linux kernel, the following vulnerability has been resolved:

sctp: dont free the ASCONFs 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 packets 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.

Weakness

The product reuses or references memory after it has been freed. At some point afterward, the memory may be allocated again and saved in another pointer, while the original pointer references a location somewhere within the new allocation. Any operations using the original pointer are no longer valid because the memory “belongs” to the code that operates on the new pointer.

Affected Software

Potential Mitigations

References

• https://git.kernel.org/stable/c/2b324ba3494ae958cba16a453e3e71489b4de7fc
• https://git.kernel.org/stable/c/74e8f3e7114f0e26d1b2c4c048044db9fcc27603
• https://git.kernel.org/stable/c/85aca407c560aba81b5ce9d3d6cf94c74077d19b
• https://git.kernel.org/stable/c/9b2854f86f0b56e9027d68e7a3fc909d1a9b566f
• https://git.kernel.org/stable/c/a63afa1f9b12d5293cbe0b77fd45dc0632533a13
• https://git.kernel.org/stable/c/a9ce31be4cb1a5dd82b3e0a1d0c3e7cbdcd31293
• https://git.kernel.org/stable/c/d136b29bf91dd8e3161281b87de597b7311d9462
• https://git.kernel.org/stable/c/fedeb4468987bcaff85fe3061de5ae052d414740
• https://matrix.tencent.com/en/2026/08/06/sctphantom-CVE-2026-64564
• http://www.openwall.com/lists/oss-security/2026/08/06/13
• http://www.openwall.com/lists/oss-security/2026/08/06/3
• http://www.openwall.com/lists/oss-security/2026/08/06/4
• http://www.openwall.com/lists/oss-security/2026/08/07/1
• http://www.openwall.com/lists/oss-security/2026/08/07/2
• http://www.openwall.com/lists/oss-security/2026/08/07/8