NIST deprecates RSA-2048 from 2030. Find every one of them before attackers do.
☕
☕ Maven
Not in CISA KEV
MEDIUM severity

CVE-2026-3260 — undertow-core

MEDIUM

CVE-2026-3260 is a medium-severity (CVSS 5.9) vulnerability in io.undertow:undertow-core. The records list no fixed version yet; check the vendor advisory below and apply the mitigations in the meantime.

Undertow: Denial of Service via Multipart/Form-Data Parsing on HTTP GET Requests

Published
Updated
Affected
1 pkg
Patched
None yet
Exploits
None indexed
Exploitation data as of Sep 10, 2026 · OSV.dev, NVD, FIRST.org (EPSS)

Real-World Exposure

1 pkg affected
☕io.undertow:undertow-core

Real-time download stats are indexed for npm and PyPI packages. This vulnerability affects Maven packages — download data is not available via public APIs for these ecosystems.

Description

A flaw was found in Undertow. A remote attacker could exploit this vulnerability by sending an HTTP GET request containing multipart/form-data content. If the underlying application processes parameters using methods like getParameterMap(), the server prematurely parses and stores this content to disk. This could lead to resource exhaustion, potentially resulting in a Denial of Service (DoS).

Affected Packages

1 total
EcosystemPackageVulnerable rangeFix
☕Mavenio.undertow:undertow-coreall versionsNo fix

Detection & mitigation playbook

Open-source dependency

  1. Detect

    Scan your dependency tree (package-lock.json, pnpm-lock.yaml, requirements.txt, go.sum, etc.) for io.undertow:undertow-core, including transitive dependencies — a direct dependency you never call can still pull in a vulnerable version.

  2. Remediation status

    The records we use list no patched version of io.undertow:undertow-core for CVE-2026-3260. Check the maintainer's advisory, and where your build allows, override or pin the dependency away from the vulnerable range.

  3. Mitigate without a patch

    Cap what an attacker can consume: apply request size, rate and timeout limits in front of the affected component, and run it with memory and CPU limits so exhaustion degrades one worker rather than the whole service.

Fixing This On Your OS

If you run this on a Linux distribution, patch through your package manager against the distro's own security advisory below — it tracks the exact backported fix for your release, which can ship on a different timeline (and sometimes a different severity) than the upstream project.

Red Hat

This CVE has been marked as Rejected by the assigning CNA.

Workaround published by Red Hat
Mitigation for this issue is either not available or the currently available options do not meet the Red Hat Product Security criteria comprising ease of use and deployment, applicability to widespread installation base, or stability.
Source: Red Hat security advisory for CVE-2026-3260 (CC BY 4.0)

Frequently Asked Questions

A flaw was found in Undertow. A remote attacker could exploit this vulnerability by sending an HTTP GET request containing multipart/form-data content. If the underlying application processes parameters using methods like `getParameterMap()`, the server prematurely parses and stores this content to disk. This could lead to resource exhaustion, potentially resulting in a Denial of Service (DoS).
O3 Security · Impact-Aware SCA

Is CVE-2026-3260 in your dependencies?

Find it across Maven, including transitive dependencies.

Scan my dependencies How O3 SCA works
CVE-2026-3260: undertow-core DoS (Medium 5.9)