CVE-2026-72021 ipvs: use parsed transport offset in SCTP state lookup
Incorrect SCTP state tracking in Linux kernel IPVS for IPv6 packets with extension headers causes improper connection state transitions and counter updates.
- Exploited in the wild
- Not known
- Login needed
- Not needed
- Attackable
- Over the internet
- Victim action needed
- Not needed
- Fix
- Available
What is CVE-2026-72021?
CVE-2026-72021 is a high-severity vulnerability in Linux, published on 15 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:
ipvs: use parsed transport offset in SCTP state lookup
set_sctp_state() reads the SCTP chunk header again in order to drive the IPVS SCTP state table. For IPv6 it computes the offset with sizeof(struct ipv6hdr), while the surrounding IPVS code uses iph.len from ip_vs_fill_iph_skb(), where ipv6_find_hdr() has already skipped extension headers and found the real transport header.
This makes the state machine read from the wrong offset for IPv6 SCTP packets that carry extension headers. For example, an INIT packet with an 8-byte destination options header can be scheduled correctly by sctp_conn_schedule(), but set_sctp_state() reads the first byte of the SCTP verification tag as a DATA chunk type. The connection then moves from NONE to ESTABLISHED instead of INIT1, gets the longer established timeout, and updates the active/inactive destination counters incorrectly. This happens even though the SCTP handshake has not completed.
Use the parsed transport offset passed down from ip_vs_set_state() for the SCTP chunk-header lookup. For IPv4 and IPv6 packets without extension headers this preserves the existing offset.
Weakness: CWE-20
Which versions are affected by CVE-2026-72021?
How do I fix CVE-2026-72021?
Apply the vendor's patch.
Is CVE-2026-72021 being exploited?
There is no known exploitation of CVE-2026-72021 in the wild and no public exploit code.
Sources
Also known as BELL-CVE-2026-72021, DEBIAN-CVE-2026-72021, GHSA-vp82-2jx6-f675, UBUNTU-CVE-2026-72021.