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VulnerabilityPublished Updated

CVE-2026-23204: Linux kernel · net/sched: cls_u32: use skb_header_pointer_careful()

Affects Linux kernelSource CVE Database V5

0

Not known to be exploited · CVSS 7.1 High · fixed in e41a23e61259f5526af875c3b86b3d42a9bae0e5 : patch Linux kernel soon.

Data as of 26 Oct 2026, 12:55 UTC

CVSS 3.1 base score
7.1High
How severe the flaw is on the 0–10 CVSS scale.
EPSS
0.1% chance of exploitation in 30 days – higher than 4% 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
Limited control over the software or limited information exposure

CISA SSVC assessment, 2026-06-16.

Patch
Available – fixed in e41a23e61259f5526af875c3b86b3d42a9bae0e5, cfa745830e45ecb75c061aa34330ee0cac941cc7, cabd1a976375780dabab888784e356f574bbaed8 +4
CVSS:3.1/AV:L/AC:L/PR:L/UI:N/S:U/C:H/I:N/A:H

Exploitation evidence

  1. Disclosed: evidence found.

    CVE published 14 Feb 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 to a fixed release listed under Affected software.

Affected software

ProductAffectedFixed in
LinuxLinuxAffected
  • ≥ fbc2e7d9cf49e0bf89b9e91fd60a06851a855c5d, < e41a23e61259f5526af875c3b86b3d42a9bae0e5
Fixed in
  • e41a23e61259f5526af875c3b86b3d42a9bae0e5
LinuxLinuxAffected
  • ≥ fbc2e7d9cf49e0bf89b9e91fd60a06851a855c5d, < cfa745830e45ecb75c061aa34330ee0cac941cc7
Fixed in
  • cfa745830e45ecb75c061aa34330ee0cac941cc7
LinuxLinuxAffected
  • ≥ fbc2e7d9cf49e0bf89b9e91fd60a06851a855c5d, < cabd1a976375780dabab888784e356f574bbaed8
Fixed in
  • cabd1a976375780dabab888784e356f574bbaed8
LinuxLinuxAffected
  • ≥ fbc2e7d9cf49e0bf89b9e91fd60a06851a855c5d, < 29681ed51e737be14d18ecd1c304c57002e4b72c
Fixed in
  • 29681ed51e737be14d18ecd1c304c57002e4b72c
LinuxLinuxAffected
  • ≥ fbc2e7d9cf49e0bf89b9e91fd60a06851a855c5d, < 13336a6239b9d7c6e61483017bb8bdfe3ceb10a5
Fixed in
  • 13336a6239b9d7c6e61483017bb8bdfe3ceb10a5
LinuxLinuxAffected
  • ≥ fbc2e7d9cf49e0bf89b9e91fd60a06851a855c5d, < 66e4b63d61c15de6ca5332d9ca6db59a404d7136
Fixed in
  • 66e4b63d61c15de6ca5332d9ca6db59a404d7136

Description

In the Linux kernel, the following vulnerability has been resolved: net/sched: cls_u32: use skb_header_pointer_careful() skb_header_pointer() does not fully validate negative @offset values. Use skb_header_pointer_careful() instead. GangMin Kim provided a report and a repro fooling u32_classify(): BUG: KASAN: slab-out-of-bounds in u32_classify+0x1180/0x11b0 net/sched/cls_u32.c:221

References

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