CVE-2026-72408 geneve: gate GRO hint in geneve_gro_complete() on gs->gro_hint
An attacker can trigger an out-of-bounds read in the Linux kernel Geneve driver by sending crafted packets, potentially causing a crash or information disclosure.
- Exploited in the wild
- Not known
- Login needed
- Not needed
- Attackable
- Over the internet
- Victim action needed
- Not needed
- Fix
- Available
What is CVE-2026-72408?
CVE-2026-72408 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:
geneve: gate GRO hint in geneve_gro_complete() on gs->gro_hint
geneve_gro_receive() reads the GRO hint through geneve_sk_gro_hint_off(), which honours it only when the socket enabled IFLA_GENEVE_GRO_HINT (gs->gro_hint). geneve_gro_complete() instead calls the low-level geneve_opt_gro_hint_off() and acts on the hint unconditionally.
On a tunnel without the hint, receive aggregates the frames as plain ETH_P_TEB while complete still honours an attacker-supplied hint option: it inflates gh_len by gro_hint->nested_hdr_len (u8) and redirects the dispatch type, so the inner gro_complete handler runs at nhoff + gh_len, an offset receive never pulled nor validated, reading out of bounds of the skb head:
BUG: KASAN: slab-out-of-bounds in ipv6_gro_complete (net/ipv6/ip6_offload.c:196) Read of size 1 at addr ffff88800fe91980 by task exploit/153 ipv6_gro_complete (net/ipv6/ip6_offload.c:196) geneve_gro_complete (drivers/net/geneve.c:965) udp_gro_complete (net/ipv4/udp_offload.c:940) inet_gro_complete (net/ipv4/af_inet.c:1621) __gro_flush (net/core/gro.c:306)
Gate the complete path on gs->gro_hint too via geneve_sk_gro_hint_off(), so both paths agree. Tunnels that enable the hint are unaffected.
Which versions are affected by CVE-2026-72408?
How do I fix CVE-2026-72408?
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-2026-72408 being exploited?
There is no known exploitation of CVE-2026-72408 in the wild and no public exploit code.
Sources
Also known as DEBIAN-CVE-2026-72408, GHSA-p4xr-mfr6-cf8x, UBUNTU-CVE-2026-72408.