`CVE-2024-4027`

Severity	7.5 High CVSS 3.1 2 scores
Fixed in	`2.2.39.Final`, `2.4.0.Beta1`, `2.3.21.Final`
Weakness	Improper input validation (CWE-20)
Published	30 Jan 2026
Updated	4 Nov 2026

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.

CWE-770

Exploitation status

No public exploit

No exploit has been reported in the sources we check.

CISA KEV not listed
VulnCheck KEV not listed
CISA Vulnrichment exploitation: none
Indexed PoC none indexed
EPSS 0.40% chance in 30 days

Waratek protection

No exploit published

Within Waratek scope. In the sources we check, nobody has published exploit code for this CVE or reported it being exploited.

A public code fix exists: undertow-io/undertow #1860.

Protection none
Action unverified
Review automated Upstream data
Record active

Decided by	Exploit code for this candidate, published in a reviewed catalogue or a GitHub repository with 5 or more stars, or in use per CISA or VulnCheck; not only a CISA verdict, a forecast, or nothing at all
Finding	This CVE is not listed in CISA KEV or VulnCheck KEV, CISA Vulnrichment records no active exploitation, no reviewed exploit catalogue carries an entry for it, and no GitHub PoC repository for it has 5 or more stars. Nobody has published exploit code worth tracing, so it is not a candidate for a rule ahead of the ones where somebody has; an upstream fix path does exist, so the remediation half of the candidacy still holds. This is a statement about what has been published, not about whether the defect is reachable or serious.
Candidate fix	https://bugzilla.redhat.com/show_bug.cgi?id=2276410 : a Red Hat bug: the triage, which links onward to the fix

Decided by

Exploit code for this candidate, published in a reviewed catalogue or a GitHub repository with 5 or more stars, or in use per CISA or VulnCheck; not only a CISA verdict, a forecast, or nothing at all

Finding

This CVE is not listed in CISA KEV or VulnCheck KEV, CISA Vulnrichment records no active exploitation, no reviewed exploit catalogue carries an entry for it, and no GitHub PoC repository for it has 5 or more stars. Nobody has published exploit code worth tracing, so it is not a candidate for a rule ahead of the ones where somebody has; an upstream fix path does exist, so the remediation half of the candidacy still holds. This is a statement about what has been published, not about whether the defect is reachable or serious.

Candidate fix

https://bugzilla.redhat.com/show_bug.cgi?id=2276410 : a Red Hat bug: the triage, which links onward to the fix

CVSS

7.5 HIGH v3.1 CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:N/I:N/A:H 2 metrics

We show the highest score from the newest CVSS version. Scores from different versions can't be compared, and the first score listed is sometimes a 0.0 placeholder.

Version Score Band Vector Assigner Type

CVSS 3.1 7.5 HIGH CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:N/I:N/A:H secalert@redhat.com Secondary published

CVSS 3.1 7.5 HIGH CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:N/I:N/A:H redhat-SADP Secondary

Version	Score	Band	Vector	Assigner	Type
CVSS 3.1	7.5	HIGH	`CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:N/I:N/A:H`	secalert@redhat.com	Secondary	published
CVSS 3.1	7.5	HIGH	`CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:N/I:N/A:H`	redhat-SADP	Secondary

Affected software and releases

Oracle advisories

Advisory	Type	Quarter	Products Oracle names in its risk matrix
Oracle Critical Patch Update April 2026 ↗	CPU	2026-Q2	Oracle Communications / Alarms, KPI, and Measurements (Undertow) (25.1.200) Oracle Communications / Install (Undertow) (25.1.100, 25.1.200)

Advisory

Type

Quarter

Products Oracle names in its risk matrix

Oracle Critical Patch Update April 2026 ↗

CPU

2026-Q2

Oracle Communications / Alarms, KPI, and Measurements (Undertow) (25.1.200)
Oracle Communications / Install (Undertow) (25.1.100, 25.1.200)

Oracle components and versions

Family	Component	Versions, as Oracle lists them	Read as
Oracle Communications	Alarms, KPI, and Measurements (Undertow)	25.1.200	25.1.200
Oracle Communications	Install (Undertow)	25.1.100, 25.1.200	25.1.100 · 25.1.200

Family

Component

Versions, as Oracle lists them

Read as

Oracle Communications

Alarms, KPI, and Measurements (Undertow)

25.1.200

Oracle Communications

Install (Undertow)

25.1.100, 25.1.200

25.1.100 · 25.1.200

Maven packages

Affected and fixed versions, from OSV.dev

Package Introduced Fixed Last affected

io.undertow:undertow-core 0 2.2.39.Final unbounded

io.undertow:undertow-core 2.4.0.Alpha1 2.4.0.Beta1 unbounded

io.undertow:undertow-core 2.3.0.Alpha1 2.3.21.Final unbounded

Package	Introduced	Fixed	Last affected
`io.undertow:undertow-core`	0	`2.2.39.Final`	unbounded
`io.undertow:undertow-core`	2.4.0.Alpha1	`2.4.0.Beta1`	unbounded
`io.undertow:undertow-core`	2.3.0.Alpha1	`2.3.21.Final`	unbounded

Products and versions

1 product, 3 version entries

Source	Vendor	Product	Scheme	Affected versions
osv	io.undertow	undertow-core	generic	＜ 2.2.39 · ≥ 2.3.0 and ＜ 2.3.21 · ≥ 2.4.0 and ＜ 2.4.0

Source

Vendor

Product

Scheme

Affected versions

osv

io.undertow

undertow-core

generic

＜ 2.2.39 · ≥ 2.3.0 and ＜ 2.3.21 · ≥ 2.4.0 and ＜ 2.4.0

References

URL	Tags
https://bugzilla.redhat.com/show_bug.cgi?id=2276410	bugzilla
https://github.com/undertow-io/undertow/pull/1860	WEB
https://github.com/undertow-io/undertow/pull/1882	WEB
https://github.com/undertow-io/undertow/pull/1894	WEB
https://github.com/undertow-io/undertow/commit/6b7c18481ce65ae4012d92fe2b7f17a21ef4d70b	WEB
https://github.com/undertow-io/undertow/commit/8318dd36fdc2c9842baf10c5f1bfbb3bc23f75e7	WEB
https://github.com/undertow-io/undertow/commit/cb854c779b9e2368c3c274ebd7217c8e75d505be	WEB
https://github.com/undertow-io/undertow/commit/fb14baa51b611a4a9f755f1d8b07d6e12eac68e3	WEB
https://access.redhat.com/security/cve/CVE-2024-4027	WEB
https://github.com/undertow-io/undertow	PACKAGE

URL

Timeline

Published	2026-01-30	By the CVE Program.
NVD record modified	2026-11-04	NVD's own last-modified date for this record.

Published

2026-01-30

By the CVE Program.

NVD record modified

2026-11-04

NVD's own last-modified date for this record.

How VRT decided (17 of 24 rules ran)

17 of 24 rules ran. The rest didn't run because an earlier rule had already settled the CVE.

# Rule Outcome Status Detail

identity: Does this identifier describe a vulnerability at all? the first rule that matches decides

1 rejected no match CVE Program withdrawal of this identifier

scope: Is it a vulnerability Waratek protects? the first rule that matches decides

2 armr-patch-file no match An ARMR patch file on disk for this CVE

3 armr-secure-rule-file no match An ARMR security-rule template on disk for this CVE

4 manual-classification no match A researcher's recorded decision for this specific CVE

5 manual classification no match Manual classification of this CVE in the legacy dataset

6 non-java-upstream no match A root cause in non-Java code: an OS kernel, a C library, or a bundled runtime

7 oracle-component no match The defect being in a component of a tracked product the agent does not reach: JavaFX, the Java SE installer, the JInitiator browser plug-in, the native WebLogic proxy plug-in, or a native part of Oracle Application Server or Collaboration Suite (HTTP Server, Web Cache, Internet Directory, mail and calendar servers). Oracle gives these no CPE of their own and names them only in the description.

8 java-client-side no match Oracle's own risk-matrix note saying the CVE is reached only through untrusted code in the Java sandbox (applets, Web Start) or only through a client installation of Java, so a server running its own trusted code is not exposed

9 osv-maven matched In scope Maven packages: io.undertow:undertow-core

10 cna-maven-package not reached An affected Maven artifact named by the CNA itself

11 known-cpe-product not reached An NVD CPE naming a product ARMR tracks

12 cna-cpe-product not reached A CPE the CNA published naming a tracked product. Oracle publishes these on advisory day, months before NVD.

13 oracle-advisory-family not reached A tracked product family named in Oracle's own risk matrix. CPE cannot carry a suite name, only a module.

14 cna-named-product not reached A tracked product named in words by the CVE's own CNA, on a record with no CPE yet. Apache and Eclipse publish these on advisory day, before NVD adds CPE data.

15 non-deployable-product not reached The only affected product being a sealed appliance image, where Java runs but no -javaagent can be attached

16 unmatched-product not reached No tracked product matched above, and none present at all

disposition: What do we do about one that is? every rule runs

17 patch-hint matched Mitigation candidate References include candidate fix URL (bugzilla tier): https://bugzilla.redhat.com/show_bug.cgi?id=2276410

18 open-source-maven skipped The affected package being open source on Maven, so the fix can be read

19 poc-derivable skipped An indexed exploit clearing the evidence bar to reverse-engineer, where there is no source to read

20 no-exploit skipped Nothing to build a rule from yet: no published exploit, no CISA record of exploitation and no source-level change to read

21 secure-rule-match no match A vulnerability class already blocked by an ARMR security rule

22 exploited-no-fix-or-poc skipped Somebody exploiting this CVE (a CISA or VulnCheck KEV listing, or a CISA verdict of active exploitation), with no fix, source code or PoC to build a rule from

23 below-action-threshold no match Severity is HIGH — only MEDIUM/LOW are deprioritized

24 no-exploit-published decided it matched No exploit published No exploit code has been published, and an upstream fix path does exist, so the remediation half of the candidacy still holds.

NVD ↗ · CVE.org ↗