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Advisory record · GHSA-33hj-rcmx-86mv

Undertow Servlets Vulnerable to Remote DoS via OutOfMemoryError when Passed Large Parameter Names

CVSS 7.5 HighEPSS 0.0040 · 34th percentile

Published by the GitHub Advisory Database at 30 Jan 2026, 15:31 UTC. agentprime has not analysed this yet, so whether it affects any app is not known.

PackageEcosystemAffectedFixed in
io.undertow:undertow-coreMaven<2.2.39.Final || >=2.4.0.Alpha1, <2.4.0.Beta1 || >=2.3.0.Alpha1, <2.3.21.Final2.2.39.Final, 2.4.0.Beta1, 2.3.21.Final
Identifiers
GHSA-33hj-rcmx-86mv · CVE-2024-4027
Weakness (CWE)
CWE-20 · CWE-770
Tags
Published
30 Jan 2026
Updated
25 Feb 2026

Machine-written summary

Summary written by Claude Haiku from the source advisory. Not reviewed by a person.

Undertow (io.undertow:undertow-core) versions before 2.2.39.Final, from 2.3.0.Alpha1 before 2.3.21.Final, and from 2.4.0.Alpha1 before 2.4.0.Beta1 are affected. An unauthenticated remote client can send a request with very large parameter names to servlets that call getParameterNames(), causing an OutOfMemoryError and a denial of service. Upgrade to 2.2.39.Final, 2.3.21.Final, 2.4.0.Beta1, or later. The source gives few details on workarounds.

Written 3 Nov 2026.

Not analysed yet

We haven’t published our analysis of this Advisory yet. Once a person has reviewed it, this page will say what’s vulnerable, what has to be true for your app to be affected, and how to check.

Severity and exploitation

ScoreRatingCVSSVectorSource
7.5 High 3.1 CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:N/I:N/A:H CNA (redhat)
  • CISA KEV Not listed.
  • EPSS 0.0040, the 34th percentile, on 12 Nov 2026: FIRST’s estimate of the chance of exploitation in the next 30 days.

Timeline

  1. 30 Jan 2026, 14:25 UTC Confirmed by the CVE List
  2. 30 Jan 2026, 15:16 UTC Confirmed by NVD
  3. 31 Oct 2026, 14:21 UTC First seen by agentprime
  4. 31 Oct 2026, 14:21 UTC Confirmed by OSV

Sources

Facts on this page come from the GitHub Advisory Database (CC-BY 4.0), OSV and the other sources listed, as published. We don’t reproduce full advisory descriptions, which can contain exploit code.