CVE-2026-53250: Linux kernel · xsk: cache csum_start/csum_offset to fix TOCTOU in xsk_skb_metadata()
Affects Linux kernelSource CVE Database V5
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
- 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:HExploitation evidence
Disclosed: evidence found.
CVE published 25 Jun 2026
Detectable: no evidence on record.
No public nuclei template indexed
Weaponised: no evidence on record.
No public exploit code indexed in Metasploit or Exploit-DB
Exploited in the wildExploited: no evidence on record.
Not in CISA KEV and no source reports exploitation
Observed by OffSeq MirageSeen by 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
| Product | Affected | Fixed in |
|---|---|---|
| LinuxLinux | Affected
| Fixed in
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| LinuxLinux | Affected
| Fixed in
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| LinuxLinux | Affected
| Fixed in
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| LinuxLinux | Affected
| Fixed in
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| LinuxLinux | Affected
| 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
- git.kernel.org/stable/c/eb778aed8a9b2381668fcb1247ae4fa011224768 (opens in a new tab)
- git.kernel.org/stable/c/0dfe05b938435892875e07771170051346412df9 (opens in a new tab)
- git.kernel.org/stable/c/bfdfd2706d5fb2cd496a1506e680daf979309c8b (opens in a new tab)
- git.kernel.org/stable/c/22ba97ea9cc1f63a0d0244fae38057ed452b6ac7 (opens in a new tab)