In the Linux kernel, the following vulnerability has been resolved: fou: Don't allow 0 for…
CVE-2026-23083 is a high-severity improper input validation vulnerability in Linux, with a CVSS 3.1 base score of 7.8 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 c7498f9bc390479ccfad7c7f2332237ff4945b03, 611ef4bd9c73d9e6d87bed57a635ff1fdd8c91ea, 6e983789b7588ee59cbf303583546c043bad8e19 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 c7498f9bc390479ccfad7c7f2332237ff4945b03 or 611ef4bd9c73d9e6d87bed57a635ff1fdd8c91ea or 6e983789b7588ee59cbf303583546c043bad8e19 or 1cc98b8887cabb1808d2f4a37cd10a7be7574771, whichever matches your release line, or a later version.
- Update Linux Kernel to 5.10.249 or 5.15.199 or 6.1.162 or 6.6.122, whichever matches your release line, or a later version.
Affected products and versions
| Vendor | Product | Affected versions | Fixed in |
|---|---|---|---|
| Linux | Linux | 23461551c00628c3f3fe9cf837bf53cf8f212b63 up to, but not including, c7498f9bc390479ccfad7c7f2332237ff4945b03; 23461551c00628c3f3fe9cf837bf53cf8f212b63 up to, but not including, 611ef4bd9c73d9e6d87bed57a635ff1fdd8c91ea; 23461551c00628c3f3fe9cf837bf53cf8f212b63 up to, but not including, 6e983789b7588ee59cbf303583546c043bad8e19; 23461551c00628c3f3fe9cf837bf53cf8f212b63 up to, but not including, 1cc98b8887cabb1808d2f4a37cd10a7be7574771; 23461551c00628c3f3fe9cf837bf53cf8f212b63 up to, but not including, b7db31a52c3862a1a32202a273a4c32e7f5f4823; 23461551c00628c3f3fe9cf837bf53cf8f212b63 up to, but not including, 9b75dff8446ec871030d8daf5a69e74f5fe8b956; 23461551c00628c3f3fe9cf837bf53cf8f212b63 up to, but not including, 7a9bc9e3f42391e4c187e099263cf7a1c4b69ff5; 3.18 | c7498f9bc390479ccfad7c7f2332237ff4945b03, 611ef4bd9c73d9e6d87bed57a635ff1fdd8c91ea, 6e983789b7588ee59cbf303583546c043bad8e19, 1cc98b8887cabb1808d2f4a37cd10a7be7574771, b7db31a52c3862a1a32202a273a4c32e7f5f4823, 9b75dff8446ec871030d8daf5a69e74f5fe8b956 |
| Siemens | SIMATIC S7-1500 CPU 1518-4 PN/DP MFP (6ES7518-4AX00-1AB0) | V3.1.6 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; V3.1.7 and later | Not stated |
| Siemens | SIMATIC S7-1500 CPU 1518F-4 PN/DP MFP (6ES7518-4FX00-1AB0) | V3.1.6 and later; V3.1.7 and later | Not stated |
| Siemens | SIMATIC S7-1500 CPU 1518F-4 PN/DP MFP (6ES7518-4FX00-1AC0) | V3.1.6 and later; V3.1.7 and later | Not stated |
| Siemens | SIPLUS S7-1500 CPU 1518-4 PN/DP MFP (6AG1518-4AX00-4AC0) | V3.1.6 and later; V3.1.7 and later | Not stated |
| Linux | Linux Kernel | 3.18 up to, but not including, 5.10.249; 5.11 up to, but not including, 5.15.199; 5.16 up to, but not including, 6.1.162; 6.2 up to, but not including, 6.6.122; 6.7 up to, but not including, 6.12.68; 6.13 up to, but not including, 6.18.8; 6.19 | 5.10.249, 5.15.199, 6.1.162, 6.6.122, 6.12.68, 6.18.8 |
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
- HighData or code can be modified at will.
- 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:H/A:H. Scored by NVD.
Official description
In the Linux kernel, the following vulnerability has been resolved: fou: Don't allow 0 for FOU_ATTR_IPPROTO. fou_udp_recv() has the same problem mentioned in the previous patch. If FOU_ATTR_IPPROTO is set to 0, skb is not freed by fou_udp_recv() nor "resubmit"-ted in ip_protocol_deliver_rcu(). Let's forbid 0 for FOU_ATTR_IPPROTO.
Source: the CVE record as published by its numbering authority, via NVD and CVE.org.
The underlying weakness: Improper Input Validation
The product receives input or data, but it does not validate or incorrectly validates that the input has the properties that are required to process the data safely and correctly.
How developers prevent this class of flaw
- Consider using language-theoretic security (LangSec) techniques that characterize inputs using a formal language and build recognizers for that language. This effectively requires parsing to be a distinct layer that effectively enforces a boundary between raw input and internal data representations, instead of allowing parser code to be scattered throughout the program, where it could be subject to errors or inconsistencies that create weaknesses.
- Use an input validation framework such as Struts or the OWASP ESAPI Validation API. Note that using a framework does not automatically address all input validation problems; be mindful of weaknesses that could arise from misusing the framework itself (CWE-1173).
- Understand all the potential areas where untrusted inputs can enter the product, including but not limited to: parameters or arguments, cookies, anything read from the network, environment variables, reverse DNS lookups, query results, request headers, URL components, e-mail, files, filenames, databases, and any external systems that provide data to the application. Remember that such inputs may be obtained indirectly through API calls.
Timeline
- CVE record published.
- CISA published its SSVC assessment (exploitation: none, automatable: no, technical impact: total).
- Record last changed materially (score, affected products, status or references).
References
Patches and release notes
- git.kernel.org/stable/c/1cc98b8887cabb1808d2f4a37cd10a7be7574771
- git.kernel.org/stable/c/611ef4bd9c73d9e6d87bed57a635ff1fdd8c91ea
- git.kernel.org/stable/c/6e983789b7588ee59cbf303583546c043bad8e19
- git.kernel.org/stable/c/7a9bc9e3f42391e4c187e099263cf7a1c4b69ff5
- git.kernel.org/stable/c/9b75dff8446ec871030d8daf5a69e74f5fe8b956
- git.kernel.org/stable/c/b7db31a52c3862a1a32202a273a4c32e7f5f4823
- git.kernel.org/stable/c/c7498f9bc390479ccfad7c7f2332237ff4945b03
Other references
Recent Improper Input Validation vulnerabilities
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- 9.8 Critical severity
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