CVE-2026-89565 ipip: fix skb leak in collect_md mode when metadata_dst allocation fails
A memory leak in the Linux kernel's IPIP tunnel driver can cause denial of service when metadata allocation fails in collect_md mode.
- Exploited in the wild
- Not known
- Login needed
- Not needed
- Attackable
- Local or same network only
- Victim action needed
- Not needed
- Fix
- Available
What is CVE-2026-89565?
CVE-2026-89565 is a memory corruption vulnerability in Linux, published on 11 Sep 2026. It can only be exploited from the same machine or local network, with no action from the victim.
Official description
In the Linux kernel, the following vulnerability has been resolved:
ipip: fix skb leak in collect_md mode when metadata_dst allocation fails
In collect_md mode ipip_tunnel_rcv() returns 0 without freeing the skb when ip_tun_rx_dst() fails to allocate the metadata_dst. ipip_rcv() and mplsip_rcv() are registered as xfrm_tunnel handlers, so tunnel4_rcv() and tunnelmpls4_rcv() read the zero return as "the packet has been consumed" and do not free it either. The skb is leaked.
The other tunnel drivers all dispose of the packet at this point: ip6_tunnel.c jumps to its drop label, ip_gre.c and ip6_gre.c return PACKET_REJECT, which makes gre_rcv() free the skb. Only ipip returns 0.
Jump to the existing drop label instead. It frees the skb and still returns 0, so the packet keeps being reported as consumed, which is what we want here: the outer header has already been pulled, and neither the remaining handlers nor an ICMP unreachable have any use for it.
Triggering this needs an ipip or mplsip tunnel in collect_md mode and an atomic allocation failure, which is why it has gone unnoticed.
Which versions are affected by CVE-2026-89565?
How do I fix CVE-2026-89565?
Apply the vendor's patch.
Upgrade to the fixed version. Memory-safe languages, compiler hardening and fuzzing prevent most new cases. More about Memory corruption.
Is CVE-2026-89565 being exploited?
There is no known exploitation of CVE-2026-89565 in the wild and no public exploit code.
Sources
Also known as AZL-100745, BELL-CVE-2026-89565, DEBIAN-CVE-2026-89565, GHSA-x2xj-xv7g-fj5c, UBUNTU-CVE-2026-89565.