PT-2026-52345 · Linux · Linux
Published
2026-06-25
·
Updated
2026-06-25
·
CVE-2026-53250
None
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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.
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Related Identifiers
Affected Products
Linux