CVE-2026-72417 netfilter: flowtable: Validate iph->ihl in nf_flow_ip4_tunnel_proto()
A missing validation of IP header length in the Linux kernel netfilter flowtable allows out-of-bounds access, potentially leading to crashes or code execution.
- Exploited in the wild
- Not known
- Login needed
- Not needed
- Attackable
- Over the internet
- Victim action needed
- Not needed
- Fix
- Available
What is CVE-2026-72417?
CVE-2026-72417 is a critical memory corruption 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:
netfilter: flowtable: Validate iph->ihl in nf_flow_ip4_tunnel_proto()
Add sanity check for iph->ihl field in nf_flow_ip4_tunnel_proto() before using it to compute the header size, avoiding out-of-bounds access with malformed IP headers. While at it, use iph->protocol instead of the hardcoded IPPROTO_IPIP constant when setting ctx->tun.proto and reference ctx->tun.hdr_size when updating ctx->offset.
Which versions are affected by CVE-2026-72417?
How do I fix CVE-2026-72417?
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-2026-72417 being exploited?
There is no known exploitation of CVE-2026-72417 in the wild and no public exploit code.
Sources
Also known as DEBIAN-CVE-2026-72417, GHSA-qcmg-5w5p-j7v4, UBUNTU-CVE-2026-72417.