CVE-2026-31641

Summary

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.

Affected Software

VendorProductVersion RangeStatus
LinuxLinux0ca100ff4df64f5d0f6c1dd5080c3e096786bea6 < 3e04596cba8a86cbff9c3f4bf0a524a3a488773caffected
LinuxLinux0ca100ff4df64f5d0f6c1dd5080c3e096786bea6 < 49875b360c2b83a3c226e189c502e501d83e6445affected
LinuxLinux0ca100ff4df64f5d0f6c1dd5080c3e096786bea6 < d179a868dd755b0cfcf7582e00943d702b9943b8affected
LinuxLinux6.16affected
LinuxLinux0 < 6.16unaffected
LinuxLinux6.18.23 <= 6.18.*unaffected
LinuxLinux6.19.13 <= 6.19.*unaffected
LinuxLinux7.0 <= *unaffected

Weaknesses

ADP Enrichment

kernel: rxrpc: Fix RxGK token loading to check bounds

Additional References

References