CVE-2026-72248 netfilter: flowtable: support IPIP tunnel with direct xmit
A null pointer dereference in the Linux kernel netfilter flowtable occurs when using IPIP tunnels with direct xmit, causing a system crash.
- Exploited in the wild
- Not known
- Login needed
- Not needed
- Attackable
- Over the internet
- Victim action needed
- Not needed
- Fix
- Available
What is CVE-2026-72248?
CVE-2026-72248 is a critical 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: support IPIP tunnel with direct xmit
The combination of IPIP tunnel with direct xmit, eg. bridge device, breaks because no dst_entry is provided to check the skb headroom and to set the iph->frag_off field. This leads to invalid dst usage and can trigger a crash in the tunnel transmit path.
Fix this by moving dst_cache and dst_cookie out of the runtime union so that they can be shared by neighbour, xfrm, and direct tunnel flows. For FLOW_OFFLOAD_XMIT_DIRECT tuples carrying tunnel metadata, preserve route state in these shared fields and release it through the common dst release path.
Since dst_entry is now available to the three supported xmit modes and dst_release() already deals with NULL dst, remove the xmit type check in nft_flow_dst_release(). Moreover, skip the check if the dst entry is NULL in nf_flow_dst_check() which is now the case for the direct xmit case.
Based on patch from Rein Wei <[email protected]>.
Which versions are affected by CVE-2026-72248?
How do I fix CVE-2026-72248?
Apply the vendor's patch.
Is CVE-2026-72248 being exploited?
There is no known exploitation of CVE-2026-72248 in the wild and no public exploit code.
Sources
Also known as DEBIAN-CVE-2026-72248, GHSA-mv4h-4h45-g2xr, UBUNTU-CVE-2026-72248.