CVE-2026-45940 net: stmmac: fix oops when split header is enabled
A null pointer dereference in the stmmac network driver causes a kernel oops when split header mode is enabled, leading to 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-2026-45940?
CVE-2026-45940 is a medium-severity vulnerability in Linux kernel, published on 27 May 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:
net: stmmac: fix oops when split header is enabled
For GMAC4, when split header is enabled, in some rare cases, the hardware does not fill buf2 of the first descriptor with payload. Thus we cannot assume buf2 is always fully filled if it is not the last descriptor. Otherwise, the length of buf2 of the second descriptor will be calculated wrong and cause an oops:
Unable to handle kernel paging request at virtual address ffff00019246bfc0 ... x2 : 0000000000000040 x1 : ffff00019246bfc0 x0 : ffff00009246c000 Call trace: dcache_inval_poc+0x28/0x58 (P) dma_direct_sync_single_for_cpu+0x38/0x6c __dma_sync_single_for_cpu+0x34/0x6c stmmac_napi_poll_rx+0x8f0/0xb60 __napi_poll.constprop.0+0x30/0x144 net_rx_action+0x160/0x274 handle_softirqs+0x1b8/0x1fc ...
To fix this, the PL bit-field in RDES3 register is used for all descriptors, whether it is the last descriptor or not.
Which versions are affected by CVE-2026-45940?
It affects 1 product.
Products include Linux kernel.
How do I fix CVE-2026-45940?
Apply the vendor's patch.
Is CVE-2026-45940 being exploited?
There is no known exploitation of CVE-2026-45940 in the wild and no public exploit code.
Other vulnerabilities in Linux kernel
Sources
Also known as AZL-88761, BELL-CVE-2026-45940, DEBIAN-CVE-2026-45940, GHSA-fr2g-jcmh-j266, ROOT-OS-DEBIAN-11-CVE-2026-45940, ROOT-OS-DEBIAN-12-CVE-2026-45940 and 4 more.