CVE-2026-53250

CVE-2026-53250 · xsk: cache csum_start/csum_offset to fix TOCTOU in xsk_skb_metadata()

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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, which local caching guarantees.

CVSS 7.8 · Élevée · EPSS 0,1% · Correctif disponible

Publication

2026-06-25T08:39:42.630Z

Mise à jour

2026-10-19T19:57:31.573Z

Pile logicielle: system

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