CVE-2026-31503

UDP service disruption via wildcard bind conflict

Published Apr 22, 2026 · Updated Apr 22, 2026

Improper UDP bind handling in affected Linux Kernel releases allows local users to create conflicting wildcard socket bindings. The UDP bind path switches to hash2 after more than ten same-port sockets, then checks address-and-port keys without preserving the port-wide wildcard conflict test. A low-privilege local process can trigger the threshold and make an IPv4, IPv6, or IPv4-mapped wildcard bind succeed despite existing specific-address bindings, disrupting UDP service availability.

CVSS severity5.5
Medium
EPSS probability0.12%
Next 30 days · Sep 16, 2026
Known exploitationUnconfirmed
Based on sourced intelligence
Hinoki checkNot available
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Summary

What happened

Improper UDP bind handling in affected Linux Kernel releases allows local users to create conflicting wildcard socket bindings. The UDP bind path switches to hash2 after more than ten same-port sockets, then checks address-and-port keys without preserving the port-wide wildcard conflict test. A low-privilege local process can trigger the threshold and make an IPv4, IPv6, or IPv4-mapped wildcard bind succeed despite existing specific-address bindings, disrupting UDP service availability.

The record

CVE
CVE-2026-31503
Published
Apr 22, 2026
Updated
Apr 22, 2026
Vendor
The Linux Kernel Organization
Product
Linux Kernel
Classifications
T1499
Attack vector
local
Privileges
authenticated

Timeline

How it unfolded

  1. Apr 22, 2026CVE publishedPublication date reported by the CVE source.
  2. Apr 22, 2026Record updatedLatest update available in the CVE record.

Exploitability

Present is not the same as exploitable

Compare your product and version with the public record. A matching version still requires validation against your environment.

Is a vulnerable build present?

Compare these published version ranges with your installed build and any vendor patches.

  1. Affected versionversion=2.6.33
  2. Affected versionversion=30fff9231fad757c061285e347b33c5149c2c2e4 <0a360f7f73a06ac88f18917055fbcc79694252d7
  3. Affected versionversion=30fff9231fad757c061285e347b33c5149c2c2e4 <18d84c45def3671d5c89fbdd5d4ab8a3217fe4b4
  4. Affected versionversion=30fff9231fad757c061285e347b33c5149c2c2e4 <2297e38114316b26ae02f2d205c49b5511c5ed55
  5. Affected versionversion=30fff9231fad757c061285e347b33c5149c2c2e4 <d6ace0dbcbb7fd285738bb87b42b71b01858c952
  6. Affected versionversion=30fff9231fad757c061285e347b33c5149c2c2e4 <e537dd15d0d4ad989d56a1021290f0c674dd8b28
  7. Affected versionversion=30fff9231fad757c061285e347b33c5149c2c2e4 <f1bed05a832ae79be5f7a105da56810eaa59a5f1

What conditions does exploitation require?

Attack vectorlocal
Required privilegesauthenticated

What is affected?

The Linux Kernel Organization · Linux Kernelversion=2.6.33; version=30fff9231fad757c061285e347b33c5149c2c2e4 <0a360f7f73a06ac88f18917055fbcc79694252d7; version=30fff9231fad757c061285e347b33c5149c2c2e4 <18d84c45def3671d5c89fbdd5d4ab8a3217fe4b4; version=30fff9231fad757c061285e347b33c5149c2c2e4 <2297e38114316b26ae02f2d205c49b5511c5ed55; version=30fff9231fad757c061285e347b33c5149c2c2e4 <d6ace0dbcbb7fd285738bb87b42b71b01858c952; version=30fff9231fad757c061285e347b33c5149c2c2e4 <e537dd15d0d4ad989d56a1021290f0c674dd8b28; version=30fff9231fad757c061285e347b33c5149c2c2e4 <f1bed05a832ae79be5f7a105da56810eaa59a5f1

Published CVSS scores

5.5UbuntuCVSS:3.1/AV:L/AC:L/PR:L/UI:N/S:U/C:N/I:N/A:H
5.5NIST NVDCVSS:3.1/AV:L/AC:L/PR:L/UI:N/S:U/C:N/I:N/A:H

CVSS describes severity. EPSS estimates exploitation probability.

Attacks

What attackers are doing with it

Daily unique IPs observed by Shadowserver honeypots for known exploited vulnerabilities (KEVs). Missing observations do not establish an absence of attacks.

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No observations available

Sep 10, 2026Sep 16, 2026
Latest reporting daySep 16, 2026
Latest daily unique IPsUnavailable
Prior 30-day averageUnavailable
SourceShadowserver honeypots (KEV)
Vectorlocal
Privilegesauthenticated
Known exploitationUnconfirmed
Public exploitUnconfirmed

Weakness, pattern, technique

T1499Endpoint Denial of Service

Public exploit references

No public exploit references are available in this record.

Labels summarize the accepted research assessment. They do not indicate a test against your environment.

Technologies

Your stack

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Your stack

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