VulnerabilityPublished 4 Feb 2026Updated 19 Oct 2026

CVE-2026-23083: Linux kernel · fou: Don't allow 0 for FOU_ATTR_IPPROTO.

Affects Linux kernelSource CVE Database V5

Not known to be exploited · fixed in c7498f9bc390479ccfad7c7f2332237ff4945b03 : update Linux kernel when convenient.

Data as of 26 Oct 2026, 17:16 UTC

Severity

Medium

Rated Medium by Threat Radar's AI analysis · No CVSS score from NVD or the CNA

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.

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, 2026-06-10.

Patch

Available – fixed in c7498f9bc390479ccfad7c7f2332237ff4945b03, b7db31a52c3862a1a32202a273a4c32e7f5f4823, 611ef4bd9c73d9e6d87bed57a635ff1fdd8c91ea +4

Exploitation evidence

Disclosed: evidence found.
CVE published 4 Feb 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.

Disclosed: The CVE record is public on cve.org. Its publication is t = 0.
Detectable: A public nuclei template can find exposed instances, for defenders and attackers alike.
Weaponised: Public exploit code exists in Metasploit or Exploit-DB, or CISA SSVC or the CVSS exploit maturity reports a public proof of concept.
Exploited in the wild: CISA KEV lists it, CISA SSVC rates exploitation active, or a source reports attacks.
Observed by OffSeq Mirage: OffSeq Mirage honeypot sensors recorded attack traffic for this CVE, or found exposed hosts without attack traffic.

Moments are spaced evenly, not to scale; a dashed line marks a gap of six months or more. Deltas count from t = 0. Sources that give only a date (CISA KEV, Exploit-DB, or a time of exactly 00:00Z) read “same day” rather than hours. Metasploit modules carry the flaw’s disclosure date, not their release date, and nuclei templates carry no date, so both appear above but not on the timeline.

What to do

Upgrade to a fixed release listed under Affected software.

Affected software

Product	Affected	Fixed in
LinuxLinux	Affected ≥ 23461551c00628c3f3fe9cf837bf53cf8f212b63, < c7498f9bc390479ccfad7c7f2332237ff4945b03	Fixed in c7498f9bc390479ccfad7c7f2332237ff4945b03
LinuxLinux	Affected ≥ 23461551c00628c3f3fe9cf837bf53cf8f212b63, < b7db31a52c3862a1a32202a273a4c32e7f5f4823	Fixed in b7db31a52c3862a1a32202a273a4c32e7f5f4823
LinuxLinux	Affected ≥ 23461551c00628c3f3fe9cf837bf53cf8f212b63, < 611ef4bd9c73d9e6d87bed57a635ff1fdd8c91ea	Fixed in 611ef4bd9c73d9e6d87bed57a635ff1fdd8c91ea
LinuxLinux	Affected ≥ 23461551c00628c3f3fe9cf837bf53cf8f212b63, < 9b75dff8446ec871030d8daf5a69e74f5fe8b956	Fixed in 9b75dff8446ec871030d8daf5a69e74f5fe8b956
LinuxLinux	Affected ≥ 23461551c00628c3f3fe9cf837bf53cf8f212b63, < 7a9bc9e3f42391e4c187e099263cf7a1c4b69ff5	Fixed in 7a9bc9e3f42391e4c187e099263cf7a1c4b69ff5
LinuxLinux	Affected ≥ 23461551c00628c3f3fe9cf837bf53cf8f212b63, < 6e983789b7588ee59cbf303583546c043bad8e19	Fixed in 6e983789b7588ee59cbf303583546c043bad8e19

AI-suggested

A fix is available and has been applied in specific Linux kernel commits. Users and administrators should update their Linux kernel to a version that includes these fixes to mitigate the vulnerability.

Description

A vulnerability in the Linux kernel's fou (Foo over UDP) subsystem was addressed by disallowing the value 0 for the FOU_ATTR_IPPROTO attribute. When FOU_ATTR_IPPROTO is set to 0, the kernel function fou_udp_recv() fails to free the associated skb buffer or resubmit it properly, potentially leading to resource management issues. This flaw has been fixed in specific Linux kernel commits.

Impact

If exploited, this vulnerability could lead to resource leaks within the kernel due to skb buffers not being freed or resubmitted correctly. The description does not specify further impact such as privilege escalation or denial of service, so the impact is limited to potential resource mismanagement.

Summary

The Linux kernel's fou_udp_recv() function mishandles the case when the FOU_ATTR_IPPROTO attribute is set to 0. Specifically, the skb buffer is neither freed nor resubmitted in ip_protocol_deliver_rcu(), causing improper resource handling. The patch forbids setting FOU_ATTR_IPPROTO to 0 to prevent this issue. This vulnerability affects Linux kernel version 3.18 and has been fixed in several commits identified by their hashes.

CWE-20Improper Input Validation (opens in a new tab)
Class weaknessLikelihood of exploit: HighCWE Top 25 (2025): #18OWASP Top 10 A05:2025: Injection (opens in a new tab)
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.
MITRE discourages mapping vulnerabilities to this broad entry; the root cause is usually a more specific weakness.
Architecture and Design · Attack Surface Reduction
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…
Architecture and Design · Libraries or Frameworks
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).
Architecture and Design · Implementation · Attack Surface Reduction
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…
OWASP Cheat Sheets
XML Security (opens in a new tab)
Mass Assignment (opens in a new tab)
Injection Prevention (opens in a new tab)
SQL Injection Prevention (opens in a new tab)
Injection Prevention in Java (opens in a new tab)
OWASP ASVS 4.0.3
V13.3.1 (opens in a new tab)
V5.1.4 (opens in a new tab)
V5.1.3 (opens in a new tab)
Attack patterns
Buffer Overflow via Environment Variables (opens in a new tab)
Server Side Include (SSI) Injection (opens in a new tab)
Cross Zone Scripting (opens in a new tab)
Command Line Execution through SQL Injection (opens in a new tab)
Object Relational Mapping Injection (opens in a new tab)
From MITRE CWE, MITRE CAPEC and OWASP (Top 10, OpenCRE).

References

Community reviews

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Exploitation evidence

What to do

Affected software

Description

AI analysisMachine-generated, updated 26 Oct 2026, 15:48 UTC

WeaknessesCWE-20

Technical details

References

Community reviews

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