CVE-2024-44940

What it actually does

The kernel issues a WARN_ON_ONCE in gue_gro_receive when receiving GUE-encapsulated packets whose inner protocol lacks a GRO handler, allowing crafted packets to trigger the warning path.

Why it matters to the business

Log spam and potential minor operational noise on systems processing untrusted network traffic; no remote code execution or data loss risk, though the warning was previously reduced from WARN_ON.

How an attack unfolds

An attacker crafts IPv4 or IPv6 packets with GUE encapsulation containing an unsupported inner protocol and sends them to a vulnerable Linux host; syzbot-style fuzzing or direct transmission triggers the WARN_ON_ONCE in the fou module GRO path. No further impact occurs beyond the warning.

How to fix it

Upgrade the Linux kernel to commit a925a200299a6dfc7c172f54da6f374edc930053 or later stable releases containing the fix; Android devices should apply the corresponding 2022-12-01 security patches for versions 10 through 13.

How to confirm the fix worked

Confirm kernel source contains the removal of WARN_ON_ONCE from gue_gro_receive and test with crafted GUE packets to verify no warning is emitted.

Typical attack path

1. Craft packet with GUE outer header and unknown inner protocol type
2. Transmit packet to target Linux system
3. gue_gro_receive is invoked during GRO processing
4. Unsupported protocol causes WARN_ON_ONCE to fire

How to detect it

Search kernel logs for the original WARN_ON_ONCE string in gue_gro_receive; examine network traces for GUE packets with unknown inner protocol types; no post-fix exploitation artifacts exist because the condition is now silent.

What your security team should do

• Apply the kernel patch or updated distribution packages immediately on all exposed systems
• Monitor for any remaining WARN_ON_ONCE occurrences in fou-related paths after upgrade
• Prioritize patching on hosts that terminate GUE tunnels or process untrusted encapsulated traffic