# CVE-2026-53250

## Summary

- **CVE ID:** CVE-2026-53250
- **Severity:** HIGH
- **CVSS Score:** 7.8 (CVSS:3.1/AV:L/AC:L/PR:L/UI:N/S:U/C:H/I:H/A:H)
- **CWE:** N/A
- **Published:** Jun 25, 2026
- **Last Modified:** Sep 14, 2026

## 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, which local
caching guarantees.

## Affected Products

- Linux — Linux (48eb03dd26304c24f03bdbb9382e89c8564e71df)
- Linux — Linux (6.8)
- Linux — Linux (0)
- Linux — Linux (6.18.36)
- Linux — Linux (7.0.13)
- Linux — Linux (7.1)
- Linux — Linux (6.12.110)

## References

- [CNA](https://git.kernel.org/stable/c/0dfe05b938435892875e07771170051346412df9)
- [CNA](https://git.kernel.org/stable/c/bfdfd2706d5fb2cd496a1506e680daf979309c8b)
- [CNA](https://git.kernel.org/stable/c/22ba97ea9cc1f63a0d0244fae38057ed452b6ac7)
- [CNA](https://git.kernel.org/stable/c/eb778aed8a9b2381668fcb1247ae4fa011224768)

## Exploitation Prediction (EPSS)

- **EPSS Score:** 0.10%
- **EPSS Percentile:** 1.2

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_Exported from OnDuty AI Vulnerability Intelligence on 2026-09-18._