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

Description

A flaw was found in Undertow. Servlets using a method that calls HttpServletRequestImpl.getParameterNames() can cause an OutOfMemoryError when the client sends a request with large parameter names. This issue can be exploited by an unauthorized user to cause a remote denial-of-service (DoS) attack.

Basic information

Type
reviewed
Severity
high
Advisory on GitHub
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Repository advisory
Source code
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Published (advisory)
2026-01-30 15:31:14 UTC
Updated
2026-02-25 20:20:30 UTC
GitHub reviewed
2026-02-01 18:07:04 UTC
NVD published
2026-01-30

EPSS Score

Score Percentile
0.30% 53.36%

CVSS Scores

Base score Version Severity Vector
7.5 3.1
CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:N/I:N/A:H Click to expand
Attack vector (AV:N)
Could be attacked over the internet or any normal routed network—not just someone sitting at the machine.
Attack complexity (AC:L)
Once they can reach the bug, pulling it off is straightforward—no weird race conditions or rare setup.
Privileges required (PR:N)
No account or special rights needed—anonymous or random user is enough.
User interaction (UI:N)
Nobody has to click “OK” or open a trap file; it can work without a victim helping.
Scope (S:U)
Damage stays in the same “trust bubble” as the broken component—no big spill into unrelated systems.
Confidentiality (C:N)
Doesn’t really leak secrets in a meaningful way.
Integrity (I:N)
Data isn’t meaningfully altered or forged.
Availability (A:H)
Could take the service down hard or make it unusable for people who depend on it.

Identifiers

CWEs

CWE id Name
CWE-770 Allocation of Resources Without Limits or Throttling

Credits

  • za-rudeboy (analyst)

Affected packages (3)

Vulnerable version ranges and first patched releases as published by GitHub.

Ecosystem Package Vulnerable range First patched Vulnerable functions
maven io.undertow:undertow-core < 2.2.39.Final 2.2.39.Final
maven io.undertow:undertow-core = 2.4.0.Alpha1 2.4.0.Beta1
maven io.undertow:undertow-core >= 2.3.0.Alpha1, < 2.3.21.Final 2.3.21.Final

References

cvelogic Threat Intelligence