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Advisory record · GHSA-95h4-w6j8-2rp8

Undertow MadeYouReset HTTP/2 DDoS Vulnerability

CVSS 7.5 HighEPSS 0.023 · 83rd percentile

Published by the GitHub Advisory Database at 2 Sept 2025, 15:31 UTC. agentprime has not analysed this yet, so whether it affects any app is not known.

PackageEcosystemAffectedFixed in
io.undertow:undertow-coreMaven<2.2.38.Final || >=2.3.0.Alpha1, <2.3.20.Final2.2.38.Final, 2.3.20.Final
Identifiers
GHSA-95h4-w6j8-2rp8 · CVE-2025-9784
Weakness (CWE)
CWE-404 · CWE-770
Tags
Published
2 Sept 2025
Updated
6 Oct 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 2.2.38.Final, and from 2.3.0.Alpha1 before 2.3.20.Final, are affected. A remote client can send malformed HTTP/2 requests that cause repeated server-side stream resets without tripping abuse counters, forcing excessive server workload and a denial of service. Upgrade to 2.2.38.Final or 2.3.20.Final.

Written 2 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 0.023, the 83rd percentile, on 13 Nov 2026: FIRST’s estimate of the chance of exploitation in the next 30 days.

Timeline

  1. 2 Sept 2025, 13:37 UTC Confirmed by the CVE List
  2. 2 Sept 2025, 14:15 UTC Confirmed by NVD
  3. 31 Oct 2026, 14:16 UTC First seen by agentprime
  4. 31 Oct 2026, 14:16 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.