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TomcatWeb server / proxy · Apache

CVE-2026-34500

MEDIUM · 6.5 CVSS v3.1 Published 2026-04-09
Fix available
A fix is available. Upgrade to 9.0.117 / 10.1.54 or later.
See remediation →
74/100
Remediation priority · Elevated
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
CLIENT_CERT authentication does not fail as expected for some scenarios when soft fail is disabled and FFM is used in Apache Tomcat. This issue affects Apache Tomcat: from 11.0.0-M14 through 11.0.20, from 10.1.22 through 10.1.53, from 9.0.92 through 9.0.116. Users are recommended to upgrade to version 11.0.21, 10.1.54 or 9.0.117, which fixes the issue.

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 · high confidence

In Apache Tomcat, when CLIENT_CERT authentication is configured with soft fail disabled and Forwarded For Magic (FFM) header handling is enabled, the server may not properly reject authentication in certain failure scenarios. This could allow certificate validation failures to be incorrectly processed, potentially permitting access when authentication should have been denied.

MitigationUpgrade Apache Tomcat to version 9.0.117, 10.1.54, or 11.0.21 to resolve the authentication bypass. If immediate upgrade is not possible, avoid using FFM with CLIENT_CERT authentication when soft fail is disabled.

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
TomcatWeb server / proxy
Affected:>= 9.0.92, < 9.0.117>= 10.1.22, < 10.1.54>= 11.0.1, < 11.0.21= 11.0.0

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
High
Privileges
None
User interaction
None
Scope
Unchanged
Confidentiality
High
Integrity
Low
Availability
None

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

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. Check Apache Tomcat version
    Locate the Tomcat installation and check the VERSION file or examine the server startup banner for the exact version number
    Affected if The version is 9.0.92 through 9.0.116, 10.1.22 through 10.1.53, 11.0.0, or 11.0.1 through 11.0.20 (these are the vulnerable versions)
  2. Verify CLIENT_CERT authentication is configured
    Examine the Tomcat connector configuration in server.xml for a connector using authentication='CLIENT-CERT' or a security constraint using CLIENT-CERT authentication method
    Affected if CLIENT_CERT authentication is configured on any connector or web application
  3. Check if soft fail is disabled
    Inspect the Tomcat connector configuration for the 'certificateVerification' attribute; a value of 'noFailed' disables soft fail, otherwise soft fail is enabled by default
    Affected if certificateVerification is set to 'noFailed' (soft fail disabled)
  4. Confirm FFM header handling is enabled
    Look for the 'allowUnsafeLegacyRenegotiation' or 'forwardedForMagic' attribute configuration in the connector; check if X-Forwarded-For header processing with magic byte handling is explicitly enabled
    Affected if FFM (Forwarded For Magic) header handling is explicitly enabled in the connector configuration

All four conditions must be present simultaneously: running a vulnerable Tomcat version AND using CLIENT_CERT authentication AND having soft fail disabled AND having FFM header handling enabled for the system to be affected by this CVE.

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
Upgrade available Upgrade to 9.0.117 / 10.1.54 / 11.0.21 or later
Fixed in 9.0.11710.1.5411.0.21
Interim mitigation

Upgrade Apache Tomcat to version 9.0.117, 10.1.54, or 11.0.21 to resolve the authentication bypass. If immediate upgrade is not possible, avoid using FFM with CLIENT_CERT authentication when soft fail is disabled.

Recommended fix High confidence

Tomcat 9.0.117 (for 9.x) or 10.1.54 (for 10.1.x) or 11.0.21 (for 11.x)

  1. 1. Identify the currently running Apache Tomcat version using the bin/version.sh script or server info in the management interface
  2. 2. Determine which major Tomcat branch (9.x, 10.1.x, or 11.x) is currently in use based on the installed version
  3. 3. For Tomcat 9.0.x installations: upgrade to version 9.0.117 or later
  4. 4. For Tomcat 10.1.x installations: upgrade to version 10.1.54 or later
  5. 5. For Tomcat 11.x installations: upgrade to version 11.0.21 or later
  6. 6. Download the corresponding binary distribution from the Apache Tomcat website (https://tomcat.apache.org/)
  7. 7. Stop the Tomcat service or application
  8. 8. Back up the existing Tomcat installation directory, including conf/ folder with server.xml, context.xml, and any custom configurations
Caveat Minor: Review release notes for any configuration changes between versions; custom valve or filter configurations in server.xml may need adjustment if API changes occurred in the minor version bump

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

Fix this in Tomcat Scoped from the published advisory
  • Consultation2.0 h
  • Implementation2.0 h
  • Testing4.0 h
  • Review / QA2.0 h
10.0 hours of engineering $1,720
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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-2026-34500 in production — separate from our analysis above.

No notes yet

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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
  • No spam, self-promotion, credentials, or personal data