CVE-2026-64564 sctp: don't free the ASCONF's own transport in DEL-IP processing
A use-after-free vulnerability in the Linux kernel SCTP implementation allows attackers to cause denial of service or potentially execute code via crafted ASCONF chunks.
- Exploited in the wild
- Not known
- Login needed
- Not needed
- Attackable
- Over the internet
- Victim action needed
- Not needed
- Fix
- Available
What is CVE-2026-64564?
CVE-2026-64564 is a critical use after free vulnerability in Linux, published on 4 Aug 2026. An attacker can exploit it over the internet without logging in, with no action from the victim.
Official 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.
Weakness: CWE-416
Which versions are affected by CVE-2026-64564?
How do I fix CVE-2026-64564?
Apply the vendor's patch.
Upgrade to the fixed version. These bugs are found with fuzzing and sanitisers and avoided by memory-safe languages. More about Use after free.
Is CVE-2026-64564 being exploited?
There is no known exploitation of CVE-2026-64564 in the wild and no public exploit code.
Public exploit code: 5 proofs of concept on GitHub.
Sources
Also known as AZL-94395, BELL-CVE-2026-64564, CLSA-2026-1787587623, DEBIAN-CVE-2026-64564, GHSA-xw85-w2q2-369x, UBUNTU-CVE-2026-64564.