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VulnerabilityPublished Updated

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

Affects Linux kernelSource CVE Database V5

0

Not known to be exploited · CVSS 7.8 High · fixed in eb778aed8a9b2381668fcb1247ae4fa011224768 : patch Linux kernel soon.

Data as of 26 Oct 2026, 13:47 UTC

CVSS 3.1 base score
7.8High
How severe the flaw is on the 0–10 CVSS scale.
EPSS
0.1% chance of exploitation in 30 days – higher than 1% of CVEsExploit Prediction Scoring System: the likelihood attackers will use this flaw soon.
CISA SSVC
Exploitation
No evidence of active exploitation and no public proof of concept
Automatable
Attackers cannot reliably automate steps 1–4 of the kill chain
Technical impact
Total control over the software or total information disclosure

CISA SSVC assessment, 2026-10-16.

Patch
Available – fixed in eb778aed8a9b2381668fcb1247ae4fa011224768, bfdfd2706d5fb2cd496a1506e680daf979309c8b, 22ba97ea9cc1f63a0d0244fae38057ed452b6ac7 +1
CVSS:3.1/AV:L/AC:L/PR:L/UI:N/S:U/C:H/I:H/A:H

Exploitation evidence

  1. Disclosed: evidence found.

    CVE published 25 Jun 2026

  2. Detectable: no evidence on record.

    No public nuclei template indexed

  3. Weaponised: no evidence on record.

    No public exploit code indexed in Metasploit or Exploit-DB

  4. Exploited in the wild: no evidence on record.

    Not in CISA KEV and no source reports exploitation

  5. Observed by OffSeq Mirage: no evidence on record.

    No attack traffic recorded by OffSeq Mirage sensors

A missing step is not evidence of safety. Sources: cve.org (opens in a new tab), the Metasploit, Exploit-DB and nuclei-templates index as of 26 Oct 2026.

What to do

Upgrade Linux kernel to eb778aed8a9b2381668fcb1247ae4fa011224768, bfdfd2706d5fb2cd496a1506e680daf979309c8b, 22ba97ea9cc1f63a0d0244fae38057ed452b6ac7 or 0dfe05b938435892875e07771170051346412df9.

Affected software

ProductAffectedFixed in
LinuxLinuxAffected
  • ≥ 48eb03dd26304c24f03bdbb9382e89c8564e71df, < eb778aed8a9b2381668fcb1247ae4fa011224768
Fixed in
  • eb778aed8a9b2381668fcb1247ae4fa011224768
LinuxLinuxAffected
  • ≥ 48eb03dd26304c24f03bdbb9382e89c8564e71df, < bfdfd2706d5fb2cd496a1506e680daf979309c8b
Fixed in
  • bfdfd2706d5fb2cd496a1506e680daf979309c8b
LinuxLinuxAffected
  • ≥ 48eb03dd26304c24f03bdbb9382e89c8564e71df, < 22ba97ea9cc1f63a0d0244fae38057ed452b6ac7
Fixed in
  • 22ba97ea9cc1f63a0d0244fae38057ed452b6ac7
LinuxLinuxAffected
  • ≥ 48eb03dd26304c24f03bdbb9382e89c8564e71df, < 0dfe05b938435892875e07771170051346412df9
Fixed in
  • 0dfe05b938435892875e07771170051346412df9
LinuxLinuxAffected
  • =6.8
Fixed in–

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.

References

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