Linux: Out-of-bounds Read
CVE-2026-23204 is a high-severity out-of-bounds read vulnerability in Linux, with a CVSS 3.1 base score of 7.1 out of 10. It can be exploited with local access to the system by an attacker with a low-privileged account, without any action from a user. The record lists versions 66e4b63d61c15de6ca5332d9ca6db59a404d7136, 29681ed51e737be14d18ecd1c304c57002e4b72c, cfa745830e45ecb75c061aa34330ee0cac941cc7 as the first without the flaw, so updating Linux to one of those releases or later removes the exposure. There is no confirmed exploitation so far. EPSS estimates a 0.16% chance of exploitation within 30 days, which is low compared with other CVEs.
High severity with no evidence of exploitation so far.
What to do
- Update Linux to 66e4b63d61c15de6ca5332d9ca6db59a404d7136 or 29681ed51e737be14d18ecd1c304c57002e4b72c or cfa745830e45ecb75c061aa34330ee0cac941cc7 or 13336a6239b9d7c6e61483017bb8bdfe3ceb10a5, whichever matches your release line, or a later version.
- Update Linux Kernel to 6.6.124 or 6.12.70 or 6.18.10, whichever matches your release line, or a later version.
Affected products and versions
| Vendor | Product | Affected versions | Fixed in |
|---|---|---|---|
| Linux | Linux | fbc2e7d9cf49e0bf89b9e91fd60a06851a855c5d up to, but not including, 66e4b63d61c15de6ca5332d9ca6db59a404d7136; fbc2e7d9cf49e0bf89b9e91fd60a06851a855c5d up to, but not including, 29681ed51e737be14d18ecd1c304c57002e4b72c; fbc2e7d9cf49e0bf89b9e91fd60a06851a855c5d up to, but not including, cfa745830e45ecb75c061aa34330ee0cac941cc7; fbc2e7d9cf49e0bf89b9e91fd60a06851a855c5d up to, but not including, 13336a6239b9d7c6e61483017bb8bdfe3ceb10a5; fbc2e7d9cf49e0bf89b9e91fd60a06851a855c5d up to, but not including, e41a23e61259f5526af875c3b86b3d42a9bae0e5; fbc2e7d9cf49e0bf89b9e91fd60a06851a855c5d up to, but not including, 8a672f177ebe19c93d795fbe967846084fbc7943; fbc2e7d9cf49e0bf89b9e91fd60a06851a855c5d up to, but not including, cabd1a976375780dabab888784e356f574bbaed8; 2.6.35 | 66e4b63d61c15de6ca5332d9ca6db59a404d7136, 29681ed51e737be14d18ecd1c304c57002e4b72c, cfa745830e45ecb75c061aa34330ee0cac941cc7, 13336a6239b9d7c6e61483017bb8bdfe3ceb10a5, e41a23e61259f5526af875c3b86b3d42a9bae0e5, 8a672f177ebe19c93d795fbe967846084fbc7943 |
| Siemens | SIMATIC S7-1500 CPU 1518-4 PN/DP MFP (6ES7518-4AX00-1AB0) | V3.1.6 and later; V3.1.5 and later; V3.1.7 and later | Not stated |
| Siemens | SIMATIC S7-1500 CPU 1518-4 PN/DP MFP (6ES7518-4AX00-1AC0) | V3.1.6 and later; V3.1.5 and later; V3.1.7 and later | Not stated |
| Siemens | SIMATIC S7-1500 CPU 1518F-4 PN/DP MFP (6ES7518-4FX00-1AB0) | V3.1.6 and later; V3.1.5 and later; V3.1.7 and later | Not stated |
| Siemens | SIMATIC S7-1500 CPU 1518F-4 PN/DP MFP (6ES7518-4FX00-1AC0) | V3.1.6 and later; V3.1.5 and later; V3.1.7 and later | Not stated |
| Siemens | SIMATIC S7-1500 TM MFP - GNU/Linux subsystem | all versions | Not stated |
| Siemens | SIPLUS S7-1500 CPU 1518-4 PN/DP MFP (6AG1518-4AX00-4AC0) | V3.1.6 and later; V3.1.5 and later; V3.1.7 and later | Not stated |
| Linux | Linux Kernel | 2.6.35.1 up to, but not including, 6.6.124; 6.7 up to, but not including, 6.12.70; 6.13 up to, but not including, 6.18.10; 2.6.35; 6.19 | 6.6.124, 6.12.70, 6.18.10 |
Version data comes from the organisation that assigned the CVE. Confirm against the vendor advisory before deciding you are unaffected.
How the severity score breaks down
- Attack vector
- LocalThe attacker needs local access or must trick a user into running something.
- Attack complexity
- LowNo special conditions are needed; the attack works reliably.
- Privileges required
- LowA basic user account is enough.
- User interaction
- NoneNo action by a victim is required.
- Scope
- UnchangedImpact stays within the vulnerable component.
- Confidentiality
- HighAll data handled by the component can be read.
- Integrity
- NoneNothing can be modified.
- Availability
- HighThe component can be taken down completely.
Vector: CVSS:3.1/AV:L/AC:L/PR:L/UI:N/S:U/C:H/I:N/A:H. Scored by NVD.
| Scoring system | Score | Severity | Scored by |
|---|---|---|---|
| CVSS 3.1 | 7.1 | High | CNA |
| CVSS 3.1 | 7.1 | High | NVD |
Official 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
Source: the CVE record as published by its numbering authority, via NVD and CVE.org.
The underlying weakness: Out-of-bounds Read
The product reads data past the end, or before the beginning, of the intended buffer.
How developers prevent this class of flaw
- Use a language that provides appropriate memory abstractions.
Timeline
- CVE record published.
- CISA published its SSVC assessment (exploitation: none, automatable: no, technical impact: partial).
- Record last changed materially (score, affected products, status or references).
References
Patches and release notes
Other references
- git.kernel.org/stable/c/29681ed51e737be14d18ecd1c304c57002e4b72c
- git.kernel.org/stable/c/66e4b63d61c15de6ca5332d9ca6db59a404d7136
- git.kernel.org/stable/c/cfa745830e45ecb75c061aa34330ee0cac941cc7
- cert-portal.siemens.com/productcert/html/ssa-019113.html
- cert-portal.siemens.com/productcert/html/ssa-082556.html
- cert-portal.siemens.com/productcert/html/ssa-457936.html
- cert-portal.siemens.com/productcert/html/ssa-784472.html
Recent Out-of-bounds Read vulnerabilities
- 7.1 High severity
- 7.0 High severity
- 7.1 High severity
- 8.1 High severity
- 7.5 High severity
- 7.5 High severity
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