CVE-2025-40337 net: stmmac: Correctly handle Rx checksum offload errors
The stmmac driver ignored hardware checksum errors, allowing corrupt packets to be treated as valid, potentially leading to data integrity issues.
- Exploited in the wild
- Not known
- Login needed
- Not needed
- Attackable
- Over the internet
- Victim action needed
- Not needed
- Fix
- Available
What is CVE-2025-40337?
CVE-2025-40337 is a high-severity vulnerability in Linux, published on 9 Dec 2025. 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: stmmac: Correctly handle Rx checksum offload errors
The stmmac_rx function would previously set skb->ip_summed to CHECKSUM_UNNECESSARY if hardware checksum offload (CoE) was enabled and the packet was of a known IP ethertype.
However, this logic failed to check if the hardware had actually reported a checksum error. The hardware status, indicating a header or payload checksum failure, was being ignored at this stage. This could cause corrupt packets to be passed up the network stack as valid.
This patch corrects the logic by checking the `csum_none` status flag, which is set when the hardware reports a checksum error. If this flag is set, skb->ip_summed is now correctly set to CHECKSUM_NONE, ensuring the kernel's network stack will perform its own validation and properly handle the corrupt packet.
Which versions are affected by CVE-2025-40337?
How do I fix CVE-2025-40337?
Apply the vendor's patch.
Is CVE-2025-40337 being exploited?
There is no known exploitation of CVE-2025-40337 in the wild and no public exploit code.
Sources
Also known as BELL-CVE-2025-40337, DEBIAN-CVE-2025-40337, GHSA-4h2c-rg8h-8jqc, ROOT-OS-DEBIAN-11-CVE-2025-40337, ROOT-OS-DEBIAN-12-CVE-2025-40337, ROOT-OS-DEBIAN-13-CVE-2025-40337 and 3 more.