CVE-2026-31641 rxrpc: Fix RxGK token loading to check bounds
An integer overflow in the Linux kernel's rxrpc module allows heap buffer overflow via unprivileged key addition, potentially leading to code execution or privilege escalation.
- 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-2026-31641?
CVE-2026-31641 is a high-severity vulnerability in Linux kernel, published on 24 Apr 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:
rxrpc: Fix RxGK token loading to check bounds
rxrpc_preparse_xdr_yfs_rxgk() reads the raw key length and ticket length from the XDR token as u32 values and passes each through round_up(x, 4) before using the rounded value for validation and allocation. When the raw length is >= 0xfffffffd, round_up() wraps to 0, so the bounds check and kzalloc both use 0 while the subsequent memcpy still copies the original ~4 GiB value, producing a heap buffer overflow reachable from an unprivileged add_key() call.
Fix this by:
(1) Rejecting raw key lengths above AFSTOKEN_GK_KEY_MAX and raw ticket lengths above AFSTOKEN_GK_TOKEN_MAX before rounding, consistent with the caps that the RxKAD path already enforces via AFSTOKEN_RK_TIX_MAX.
(2) Sizing the flexible-array allocation from the validated raw key length via struct_size_t() instead of the rounded value.
(3) Caching the raw lengths so that the later field assignments and memcpy calls do not re-read from the token, eliminating a class of TOCTOU re-parse.
The control path (valid token with lengths within bounds) is unaffected.
Which versions are affected by CVE-2026-31641?
It affects 1 product.
Products include Linux kernel.
How do I fix CVE-2026-31641?
Apply the vendor's patch.
Is CVE-2026-31641 being exploited?
There is no known exploitation of CVE-2026-31641 in the wild and no public exploit code.
Other vulnerabilities in Linux kernel
Sources
Also known as BELL-CVE-2026-31641, DEBIAN-CVE-2026-31641, GHSA-p4pm-x7ch-5mvc, UBUNTU-CVE-2026-31641.