CVE-2026-31472 xfrm: iptfs: validate inner IPv4 header length in IPTFS payload
A crafted ESP packet causes an infinite loop in the Linux kernel's IPTFS module, leading to a denial of service.
- Exploited in the wild
- Not known
- Login needed
- Any signed-in user
- Attackable
- Local or same network only
- Victim action needed
- Not needed
- Fix
- Available
What is CVE-2026-31472?
CVE-2026-31472 is a medium-severity denial of service vulnerability in Linux kernel, published on 22 Apr 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:
xfrm: iptfs: validate inner IPv4 header length in IPTFS payload
Add validation of the inner IPv4 packet tot_len and ihl fields parsed from decrypted IPTFS payloads in __input_process_payload(). A crafted ESP packet containing an inner IPv4 header with tot_len=0 causes an infinite loop: iplen=0 leads to capturelen=min(0, remaining)=0, so the data offset never advances and the while(data < tail) loop never terminates, spinning forever in softirq context.
Reject inner IPv4 packets where tot_len < ihl*4 or ihl*4 < sizeof(struct iphdr), which catches both the tot_len=0 case and malformed ihl values. The normal IP stack performs this validation in ip_rcv_core(), but IPTFS extracts and processes inner packets before they reach that layer.
Weakness: CWE-835
Which versions are affected by CVE-2026-31472?
It affects 1 product.
Products include Linux kernel.
How do I fix CVE-2026-31472?
Apply the vendor's patch.
Upgrade, then put limits on request size, rate and nesting depth so one client cannot exhaust the service. More about Denial of service.
Is CVE-2026-31472 being exploited?
There is no known exploitation of CVE-2026-31472 in the wild and no public exploit code.
Other vulnerabilities in Linux kernel
Sources
Also known as BELL-CVE-2026-31472, DEBIAN-CVE-2026-31472, GHSA-j49f-wwvq-pvp4, UBUNTU-CVE-2026-31472.