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TomcatWeb server / proxy · Apache

CVE-2026-59083

CRITICAL · 9.1 CVSS v3.1 Published 2026-07-14
Fix available
A fix is available. Upgrade to after 11.0.23 or later.
See remediation →
100/100
Remediation priority · Urgent
Remotely reachable No privileges Zero-click 5 weeks old

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
Improper Handling of URL Encoding (Hex Encoding) vulnerability in Apache Tomcat's rewrite valve allowed security constraint bypass for some configurations. This issue affects Apache Tomcat: from 11.0.0-M1 through 11.0.23, from 10.1.0-M1 through 10.1.56, from 9.0.0.M1 through 9.0.119, from 8.5.0 through 8.5.100. Other versions that have reached end of support may also be affected. Users are recommended to upgrade to version 11.0.24, 10.1.57 or 9.0.120, which fix 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

Apache Tomcat's rewrite valve component improperly handles URL encoding (hex encoding), allowing attackers to bypass security constraints by crafting malicious URLs with encoded characters. This affects configurations using the rewrite valve for URL manipulation or security constraints.

MitigationUpgrade Apache Tomcat to version 11.0.24, 10.1.57, or 9.0.120 to obtain the fix. Review existing rewrite rules and security constraints after upgrading to confirm the bypass is no longer possible.

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:<= 8.0.0>= 8.5.0, <= 8.5.100>= 9.0.0, <= 9.0.119>= 10.1.0, <= 10.1.56>= 11.0.0, <= 11.0.23

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
High
Integrity
High
Availability
None

CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:H/I:H/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. Verify rewrite valve is enabled
    Check for the RewriteValve configuration in server.xml or context.xml files. Look for a Valve element with className="org.apache.catalina.valves.rewrite.RewriteValve" or the rewrite valve declaration in conf/Catalina/localhost/ or the main conf/server.xml
    Affected if The rewrite valve is present and enabled in the Tomcat configuration
  2. Identify installed Tomcat version
    Run the version.sh script in the Tomcat bin directory, or check the manifest in the catalina.jar file, or look at the RELEASE-NOTES file in the Tomcat installation directory
    Affected if The installed version falls within any of these ranges: 8.0.0 and below, 8.5.0 through 8.5.100, 9.0.0 through 9.0.119, 10.1.0 through 10.1.56, or 11.0.0 through 11.0.23
  3. Confirm rewrite rules are in use
    Examine the rewrite.config file in the conf/Catalina/localhost/ directory or the WEB-INF/rewrite.config path for any security constraint rules that restrict URL access patterns
    Affected if Rewrite rules defining security constraints (such as blocking or allowing specific URL patterns) are configured

A system is affected if it runs a vulnerable Tomcat version (8.5.x, 9.0.x, 10.1.x, or 11.0.x within the specified ranges), has the rewrite valve enabled, and uses rewrite rules to enforce security constraints that could be bypassed via encoded URL characters.

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 a release after 11.0.23
Interim mitigation

Upgrade Apache Tomcat to version 11.0.24, 10.1.57, or 9.0.120 to obtain the fix. Review existing rewrite rules and security constraints after upgrading to confirm the bypass is no longer possible.

Recommended fix High confidence

9.0.120 (or 10.1.57 for 10.1.x, or 11.0.24 for 11.x)

  1. Backup your current Tomcat installation and all configuration files (server.xml, context.xml, web.xml, etc.)
  2. Stop the Tomcat service
  3. Determine your current major version (8.5.x, 9.0.x, 10.1.x, or 11.x)
  4. Download the fixed version: 9.0.120 for 9.0.x, 10.1.57 for 10.1.x, or 11.0.24 for 11.x from https://tomcat.apache.org/
  5. Extract the new Tomcat version to a temporary location
  6. Copy your configuration files from the backup to the new installation
  7. Replace the old Tomcat installation directory with the new one
  8. Start the Tomcat service
Caveat Point releases typically have minimal breaking changes; review release notes for any configuration or API changes

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

Fix this in Tomcat Scoped from the published advisory
  • Consultation2.0 h
  • Implementation4.0 h
  • Testing6.0 h
  • Review / QA2.0 h
14.0 hours of engineering $2,380
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Scan for this in your stack

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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-2026-59083 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