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TomcatWeb server / proxy · Apache

CVE-2026-55955

MEDIUM · 6.5 CVSS v3.1 Published 2026-06-29
Fix available
A fix is available. Upgrade to 9.0.119 / 10.1.56 or later.
See remediation →
74/100
Remediation priority · Elevated
Remotely reachable No privileges Zero-click 7 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 Authentication vulnerability in Apache Tomcat allowed a replay attack against the EncryptionInterceptor in the cluster component. This issue affects Apache Tomcat: from 11.0.0-M1 through 11.0.22, from 10.1.0-M1 through 10.1.55, from 9.0.13 through 9.0.18, from 8.5.38 through 8.5.100, from 7.0.100 through 7.0.109. Users are recommended to upgrade to version 11.0.23, 10.1.56, 9.0.119, 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 · moderate confidence

Improper authentication in Apache Tomcat's cluster EncryptionInterceptor allows attackers to capture and replay encrypted session data, potentially gaining unauthorized access by retransmitting previously valid encrypted messages.

MitigationUpgrade Apache Tomcat to version 11.0.23, 10.1.56, or 9.0.119 (or later) to patch the replay attack vulnerability in the EncryptionInterceptor.

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:< 9.0.119>= 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
Low
Integrity
Low
Availability
None

CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:L/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. Identify Apache Tomcat installation and version
    Locate the Tomcat installation directory and check the version. Common locations include /opt/tomcat, /usr/share/tomcat, or C:\Program Files\Apache\Tomcat. In the installation directory, check the RELEASE-NOTES file or run: java -cp [catalina.jar] org.apache.catalina.util.ServerInfo
    Affected if The installed version is < 9.0.119, or >= 10.1.0 and < 10.1.56, or >= 11.0.0 and < 11.0.23
  2. Verify clustering is enabled
    Check the server.xml configuration file (typically in the conf/ directory) for a <Cluster> element. This indicates Tomcat clustering is configured.
    Affected if A <Cluster> element exists in server.xml, enabling cluster communication between Tomcat instances
  3. Confirm EncryptionInterceptor is in use
    Within the <Cluster> element in server.xml, search for the element <Interceptor className="org.apache.catalina.tribes.transport.ReplicationInterceptor"> or similar encryption-related interceptor configuration. Also check for any custom interceptor configuration that handles encrypted message transmission.
    Affected if The cluster configuration includes an EncryptionInterceptor or similar encryption mechanism for inter-node communication
  4. Check for session replication configuration
    Examine the context.xml or server.xml for <Manager pathname="" /> or <Distributable/> tag in web.xml, which enables session replication across cluster nodes.
    Affected if Session replication is enabled, meaning encrypted session data would be transmitted between cluster nodes and could be vulnerable to replay

A user is affected if they run a vulnerable Tomcat version with clustering enabled that uses EncryptionInterceptor for session replication, as this allows replay of captured encrypted session messages.

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 9.0.119 / 10.1.56 / 11.0.23 or later
Fixed in 9.0.11910.1.5611.0.23
Interim mitigation

Upgrade Apache Tomcat to version 11.0.23, 10.1.56, or 9.0.119 (or later) to patch the replay attack vulnerability in the EncryptionInterceptor.

Recommended fix High confidence

Tomcat 9.0.119 (or 10.1.56 or 11.0.23 depending on your current major version)

  1. 1. Identify the current Apache Tomcat version installed in your environment
  2. 2. For Tomcat 9.0.x: Upgrade to version 9.0.119 or later
  3. 3. For Tomcat 10.1.x: Upgrade to version 10.1.56 or later
  4. 4. For Tomcat 11.0.x: Upgrade to version 11.0.23 or later
  5. 5. Download the new version from the official Apache Tomcat repository (https://tomcat.apache.org/)
  6. 6. Test the upgrade in a non-production environment first
  7. 7. Deploy the upgraded version to production
  8. 8. If using Tomcat's clustering with EncryptionInterceptor, verify the replay attack vulnerability is mitigated
Caveat Minor - this is a patch release with bug and security fixes; review release notes for any behavioral 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
  • Testing3.0 h
  • Review / QA2.0 h
11.0 hours of engineering $1,930
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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-2026-55955 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