How severe is CVE-2023-4639?

CVE-2023-4639 has a CVSS score of 7.4/10, rated HIGH. Immediate patching is strongly recommended.

Which packages are affected by CVE-2023-4639?

CVE-2023-4639 affects the following packages: undertow (Debian:13). Ecosystems affected: Debian:13.

How do I fix CVE-2023-4639?

Update undertow to 2.3.18-1 or later, then make sure no transitive (indirect) dependency still pins the vulnerable range — O3 confirms CVE-2023-4639 is resolved across your whole dependency graph.

How do I detect CVE-2023-4639 in my Debian:13 dependencies?

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

How do I mitigate CVE-2023-4639 if there is no patch (or I can't update yet)?

If you can't upgrade right away: gate or disable the affected feature, validate untrusted input at the boundary, and avoid passing attacker-controlled data into the vulnerable path. O3's runtime protection blocks exploitation in production as an interim safeguard until the upgrade lands.

Is CVE-2023-4639 actively exploited in the wild?

No public exploit code has been indexed for CVE-2023-4639 yet. This does not mean the vulnerability cannot be exploited — absence of public exploits does not imply safety. Apply the recommended fix and use O3 Security to monitor your exposure.

What is the EPSS score for CVE-2023-4639?

CVE-2023-4639 has an EPSS (Exploit Prediction Scoring System) score of 1.1%, placing it in the 66th percentile of all CVEs. EPSS is maintained by FIRST.org and estimates the probability that a vulnerability will be exploited in the wild within the next 30 days. This score indicates relatively lower exploitation probability, though the CVSS severity should still guide your patching priority.

What type of vulnerability is CVE-2023-4639?

CVE-2023-4639 is classified as CWE-444 (CWE-444). This weakness type describe the underlying flaw category, which helps determine the potential impact and the right class of mitigation.

When was CVE-2023-4639 published, and has it been updated?

CVE-2023-4639 was published on November 17, 2024 and was last updated on February 7, 2025. Advisory data evolves as severity scores, affected ranges, and exploit intelligence are revised — always check the latest version of the advisory before acting.

Withdrawn — this advisory has been retracted

📦

📦 Debian:13

Not in CISA KEV

HIGH severity

CVE-2023-4639 — undertow

HIGHFix: undertow-io/undertow@1f93a97

CVE-2023-4639 is a high-severity (CVSS 7.4) CWE-444 vulnerability in undertow. A fix is available for undertow — see the affected versions and patch details below.

Undertow incorrectly parses cookies

Also known asGHSA-3jrv-jgp8-45v3

Published

Nov 17, 2024

Updated

Feb 7, 2025

Affected

1 pkg

Patched

1 / 1

Exploits

None indexed

Exploitation data as of Nov 7, 2026 · OSV.dev, NVD, FIRST.org (EPSS)

Exploitation Status

No confirmed exploitation observed yet

A successful exploit gives an attacker total control of the affected component, not partial access.
CISA’s own triage has not observed active exploitation or public proof-of-concept code for this CVE as of its last assessment.

Exploitation and automatability from CISA’s SSVC triage for CVE-2023-4639.

EPSS Exploitation Probability

via FIRST.org ↗

1.1%probability of exploitation in next 30 days

Lower Risk0.00%

Lower risk than most CVEs66th percentile — riskier than 66% of all scored CVEsHighest risk

Probability of exploitation in the next 30 days, from FIRST.org EPSS.

How urgent is this, really

Where this sits among everything scored

Real-World Exposure

1 pkg affected

📦undertow

Real-time download stats are indexed for npm and PyPI packages. This vulnerability affects Debian:13 packages — download data is not available via public APIs for these ecosystems.

Description

A flaw was found in Undertow, which incorrectly parses cookies with certain value-delimiting characters in incoming requests. This issue could allow an attacker to construct a cookie value to exfiltrate HttpOnly cookie values or spoof arbitrary additional cookie values, leading to unauthorized data access or modification. The main threat from this flaw impacts data confidentiality and integrity.

Affected Packages

1 total 1 fixed

Ecosystem	Package	Vulnerable range	Fix
📦Debian:13	`undertow`	all versions	2.3.18-1

Detection & mitigation playbook

Open-source dependency

Detect
Scan your dependency tree (package-lock.json, pnpm-lock.yaml, requirements.txt, go.sum, etc.) for undertow, including transitive dependencies — a direct dependency you never call can still pull in a vulnerable version.
Fix
Update undertow to 2.3.18-1 or later, then make sure no transitive (indirect) dependency still pins the vulnerable range — O3 confirms CVE-2023-4639 is resolved across your whole dependency graph.
Workarounds
If you can't upgrade right away: gate or disable the affected feature, validate untrusted input at the boundary, and avoid passing attacker-controlled data into the vulnerable path. O3's runtime protection blocks exploitation in production as an interim safeguard until the upgrade lands.

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 HatModerate

Product	Fixed in	Advisory
Migration Toolkit for Runtimes 1 on RHEL 8	`mtr/mtr-operator-bundle:1.2-23`	RHSA-2024:3919
Red Hat JBoss Enterprise Application Platform 7.4.16	`io.undertow/undertow-core:2.2.30.SP1-redhat-00001`	RHSA-2024:1677
Red Hat JBoss Enterprise Application Platform 7.4 for RHEL 8	`eap7-undertow-0:2.2.30-1.SP1_redhat_00001.1.el8eap`	RHSA-2024:1675
Red Hat JBoss Enterprise Application Platform 7.4 for RHEL 9	`eap7-undertow-0:2.2.30-1.SP1_redhat_00001.1.el9eap`	RHSA-2024:1676
Red Hat JBoss Enterprise Application Platform 7.4 on RHEL 7	`eap7-undertow-0:2.2.30-1.SP1_redhat_00001.1.el7eap`	RHSA-2024:1674
Red Hat JBoss Enterprise Application Platform 8	`undertow`	RHSA-2024:2763
Red Hat JBoss Enterprise Application Platform 8.0 for RHEL 8	`eap8-undertow-0:2.3.11-1.SP1_redhat_00001.1.el8eap`	RHSA-2024:2764

Frequently Asked Questions

O3 Security · Impact-Aware SCA

Is CVE-2023-4639 in your dependencies?

Find it across Debian:13, including transitive dependencies.

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