CVE-2026-97953 net: stmmac: fix TX descriptor availability check for TSO traffic
A flaw in the Linux kernel stmmac driver allows memory corruption via TX ring overwrite when handling highly fragmented TSO traffic, potentially leading to system crashes or code execution.
- Exploited in the wild
- Not known
- Login needed
- Not needed
- Attackable
- Over the internet
- Victim action needed
- Not needed
- Fix
- Available
What is CVE-2026-97953?
CVE-2026-97953 is a high-severity memory corruption vulnerability in Linux, published on 25 Sep 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: stmmac: fix TX descriptor availability check for TSO traffic
stmmac_tso_xmit() estimates the number of free TX descriptors required by a TSO skb as:
(skb->len - proto_hdr_len) / TSO_MAX_BUFF_SIZE + 1
which assumes the payload is split into TSO_MAX_BUFF_SIZE chunks. This underestimates the descriptors actually consumed by stmmac_tso_allocator(), since each fragment is mapped individually and so it needs at least one descriptor regardless of its size. Moreover, one descriptor is used for the L2/L3/L4 headers and, when the MSS changes, one more is consumed for the MSS context descriptor. For a highly fragmented TSO skb the check can therefore pass even when the ring has too few free slots. stmmac_tso_allocator() then writes past the available descriptors, overwriting descriptors still owned by the DMA engine, corrupting the TX ring. Add stmmac_tso_get_num_desc() to compute the exact number of descriptors needed for the header, the linear payload and each fragment, plus the MSS context descriptor when required, and use it in the availability check.
Which versions are affected by CVE-2026-97953?
How do I fix CVE-2026-97953?
Apply the vendor's patch.
Upgrade to the fixed version. Memory-safe languages, compiler hardening and fuzzing prevent most new cases. More about Memory corruption.
Is CVE-2026-97953 being exploited?
There is no known exploitation of CVE-2026-97953 in the wild and no public exploit code.
Sources
Also known as AZL-104517, BELL-CVE-2026-97953, DEBIAN-CVE-2026-97953, GHSA-4j3p-7h59-gp38, UBUNTU-CVE-2026-97953.