CVE-2026-72348: netfilter: ip6tables: mark malformed IPv6 extension headers for hotdrop
In the Linux kernel, the following vulnerability has been resolved:
netfilter: ip6tables: mark malformed IPv6 extension headers for hotdrop
The ah, hbh and rt matches check that the fixed extension header is present, then use the header length field to derive the advertised extension header length for matching.
For the ah match, add the missing advertised-length check. For hbh and rt, update the existing advertised-length checks. In all three cases, set hotdrop to true before returning false when the advertised extension header length exceeds the available skb data.
Returning false treats the packet as a rule mismatch. Set hotdrop to true and drop malformed packets so they cannot bypass rules intended to drop packets with these IPv6 extension headers.
Affected Software
Remediation
Recommended actions to resolve this vulnerability, in priority order.
- Upgrade
Upgrade
Linux kernelto a version that resolves this vulnerability.Patch netfilter: ip6tables: mark malformed IPv6 extension headers for hotdrop - Configuration
For the AH match (and in all three cases: AH, HBH, and RT), set hotdrop to true before returning false so malformed packets with advertised IPv6 extension header length exceeding available skb data are dropped (marked for hotdrop) and cannot bypass rules.
Linux kernel netfilter ip6tables (AH/HBH/RT extension header matches) hotdrop = true - Configuration
Add the missing advertised-length check for the AH match; in the HBH and RT matches update the existing advertised-length checks so the fixed extension header length is checked against available skb data and malformed packets are marked for hotdrop/drop.
Linux kernel netfilter ip6tables (AH/HBH/RT extension header matches) advertised-length check = add/extend