CVE-2026-98239 net: lan743x: fix RX checksum use-after-free
A use-after-free vulnerability in the LAN743x network driver allows attackers to cause memory corruption or system crashes via crafted multi-buffer packets.
- Exploited in the wild
- Not known
- Login needed
- Not needed
- Attackable
- Over the internet
- Victim action needed
- Not needed
- Fix
- Available
What is CVE-2026-98239?
CVE-2026-98239 is a high-severity use after free vulnerability in Linux, published on 6 Oct 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:
net: lan743x: fix RX checksum use-after-free
lan743x_rx_process_buffer() adds each non-first receive buffer to the head skb's frag_list. On the last descriptor, lan743x_rx_trim_skb() linearizes the head and frees the fragment skb metadata.
The checksum-success path then writes ip_summed through the local skb pointer, which still points to the final fragment. This causes a use-after-free write when a packet spans more than one receive buffer.
Set ip_summed on the surviving head skb instead. Multi-buffer receive can occur after a live MTU increase because existing ring entries keep their old buffer size until they are replenished.
A KUnit test invoking lan743x_rx_process_buffer() with a two-buffer packet produced a one-byte KASAN use-after-free write before this change. The same test passed after the change. The driver object also builds with W=1. This was not tested on physical LAN743x hardware.
Which versions are affected by CVE-2026-98239?
How do I fix CVE-2026-98239?
Apply the vendor's patch.
Upgrade to the fixed version. These bugs are found with fuzzing and sanitisers and avoided by memory-safe languages. More about Use after free.
Is CVE-2026-98239 being exploited?
There is no known exploitation of CVE-2026-98239 in the wild and no public exploit code.
Sources
Also known as AZL-106275, BELL-CVE-2026-98239, DEBIAN-CVE-2026-98239, GHSA-qcgj-xcvr-2727, UBUNTU-CVE-2026-98239.