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Jboss Enterprise Application PlatformApplication · Redhat

CVE-2023-5379

HIGH · 7.5 CVSS v3.1 Published 2023-12-12
Mitigation only
No fix yet — a mitigation exists. There is no fixed release. A documented workaround reduces exposure in the meantime.
See remediation →
84/100
Remediation priority · High
Remotely reachable No privileges Zero-click

Official description Straight from the sourceThe vendor's or NVD's own wording, published unedited. Authoritative, but often terse — it says what broke, rarely what to do.

NVD · unedited
A flaw was found in Undertow. When an AJP request is sent that exceeds the max-header-size attribute in ajp-listener, JBoss EAP is marked in an error state by mod_cluster in httpd, causing JBoss EAP to close the TCP connection without returning an AJP response. This happens because mod_proxy_cluster marks the JBoss EAP instance as an error worker when the TCP connection is closed from the backend after sending the AJP request without receiving an AJP response, and stops forwarding. This issue could allow a malicious user could to repeatedly send requests that exceed the max-header-size, causing a Denial of Service (DoS).

Technical summary Written by usOur analysis, written from the advisory, the CVSS vector and the affected-version data. It adds context the advisory leaves out, and never invents facts that are not in the source.

dbcve analysis · moderate confidence

In Undertow's AJP listener, when a request exceeds the configured max-header-size, JBoss EAP closes the TCP connection without returning an AJP response. This causes mod_proxy_cluster to mark the backend as an error worker, stopping request forwarding. Repeated oversized requests can trigger this condition, causing a Denial of Service.

MitigationConfigure appropriate max-header-size limits and ensure Undertow/JBoss EAP is updated to properly handle oversized AJP headers by returning an error response instead of abruptly closing the connection.

Verify against the referenced sources before acting — the references below are authoritative for this CVE, this summary is not.

Affected products & versions What the vendor confirmedThe version ranges the vendor confirmed as vulnerable. If your version sits inside a range here, treat yourself as exposed until you have upgraded.

NVD · CPE data
Jboss Enterprise Application PlatformApplication
Affected:all versions= 7.0.0
Single Sign OnApplication
Affected:= 7.0
UndertowApplication
Affected:all versions

CVSS breakdown How the score is builtThe industry scoring standard. It rates how the flaw is reached, what it takes to exploit, and what an attacker gains — the score is derived from those, not the other way round.

From the vector
Attack vector
Network
Complexity
Low
Privileges
None
User interaction
None
Scope
Unchanged
Confidentiality
None
Integrity
None
Availability
High

CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:N/I:N/A:H

Am I affected? How to checkSteps we derive from the advisory and the affected-version data, so you can decide whether this CVE reaches your setup. They are a guide, not a scan — your own configuration is the authority.

dbcve checks

Work through these to decide whether this CVE applies to you.

  1. Identify Undertow/JBoss EAP installation
    Check if the system is running JBoss EAP or Undertow by looking for process names, listening ports (common AJP port 8009), or checking installed packages
    Affected if Undertow or JBoss EAP is installed and using AJP listener on port 8009 or similar
  2. Verify AJP listener is enabled
    Examine Undertow configuration files (undertow.conf or standalone.xml/domain.xml for JBoss EAP) for AJP listener definition on port 8009 or ajp protocol binding
    Affected if AJP listener is configured and actively listening for requests
  3. Check max-header-size configuration
    Look for 'max-header-size' attribute in the AJP listener configuration section of Undertow or JBoss EAP config files
    Affected if max-header-size is set to any value and AJP listener is active - the vulnerability exists regardless of the specific value since oversized requests trigger the issue
  4. Look for evidence of connection issues
    Review server logs for unexpected TCP connection closures without AJP error response, and check mod_proxy_cluster or load balancer logs for 'error worker' status on Undertow backends
    Affected if Repeated connection drops are logged without AJP response packets, and mod_proxy_cluster marks backends as failed workers

A user is affected if they run Undertow or JBoss EAP with an AJP listener and observe unexplained backend failures or connection drops in their load balancer/proxy configuration

Generated from the published advisory. Verify against your own configuration.

Check your environment

Paste your version and any relevant configuration and it will be compared against the affected criteria above. Do not include secrets or credentials.

AI-assisted, checked against the advisory. Informational, not a guarantee.

Remediation Closing itWhat it takes to close this. Where a vendor fix exists we point at it; where none exists we say so plainly, and can build one. Effort estimates are scoped from the advisory, not from your codebase.

dbcve · scoped
Mitigation available No clean upgrade yet — mitigate in the meantime
Mitigation

Configure appropriate max-header-size limits and ensure Undertow/JBoss EAP is updated to properly handle oversized AJP headers by returning an error response instead of abruptly closing the connection.

Recommended fix Moderate confidence

Upgrade to the JBoss EAP version containing the CVE-2023-5379 fix (consult Red Hat security advisory for exact version)

  1. 1. Obtain the latest Red Hat JBoss Enterprise Application Platform security advisories for CVE-2023-5379 from access.redhat.com
  2. 2. Identify the specific JBoss EAP version that includes the fix for this Undertow vulnerability
  3. 3. Plan an upgrade to the fixed JBoss EAP version, ensuring compatibility with your current Java runtime and dependencies
  4. 4. Before upgrading in production, test the new version in a staging environment to verify application compatibility
  5. 5. After upgrading, verify that AJP listener configurations respect the max-header-size limit without causing error states
Caveat Review release notes for any breaking changes between current and target EAP versions, particularly around Undertow and AJP connector behavior

Generated from the published advisory — verify against the referenced sources before acting.

Fix this in Jboss Enterprise Application Platform Scoped from the published advisory
  • Consultation6.0 h
  • Implementation12.0 h
  • Testing10.0 h
  • Review / QA6.0 h
34.0 hours of engineering $5,940
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References Go to the primary sourcePrimary sources — vendor advisories, patches and trackers. Where our summary and a reference disagree, the reference wins.

Primary sources

Practitioner notes

Contributed

Peer-ranked notes from engineers who’ve handled CVE-2023-5379 in production — separate from our analysis above.

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What this is

A place for practitioners to share what actually worked: a mitigation you’ve tested, a configuration change, a version- or environment-specific caveat, or a link to a verified patch. The most useful notes rise to the top as peers upvote them, so the signal stays high.

What belongs here
  • Verified mitigations, workarounds, and config changes
  • Version or environment caveats, and links to real fixes
  • No weaponised exploit code, or anything meant to cause harm
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