CVE-2026-53250

/// Technical description

In the Linux kernel, the following vulnerability has been resolved:

xsk: cache csum_start/csum_offset to fix TOCTOU in xsk_skb_metadata()

The TX metadata area resides in the UMEM buffer which is memory-mapped

and concurrently writable by userspace. In xsk_skb_metadata(),

csum_start and csum_offset are read from shared memory for bounds

validation, then read again for skb assignment. A malicious userspace

application can race to overwrite these values between the two reads,

bypassing the bounds check and causing out-of-bounds memory access

during checksum computation in the transmit path.

Fix this by reading csum_start and csum_offset into local variables

once, then using the local copies for both validation and assignment.

Note that other metadata fields (flags, launch_time) and the cached

csum fields may be mutually inconsistent due to concurrent userspace

writes, but this is benign: the only security-critical invariant is

that each field's validated value is the same one used, wh

/// Remediation

Check the references section for vendor advisories, patches, and mitigation guidance. If immediate patching is not possible, review the CVSS vector to understand the attack surface and apply compensating controls such as network segmentation or access restrictions.

/// References