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Full vulnerability report · 2026
CVE-2026-43513High confidence

Apache Tomcat: LockOutRealm treats user names as case-sensitive

Apache Software Foundation · Apache Tomcat

7.5HighCVSS 3.1
Recommended action
Within 7 days

High technical severity; prioritise exposed affected systems while verifying vendor guidance.

Patch available
Distribution package intelligence

Ubuntu vendor package status

Canonical’s release and source-package findings are shown separately from local repository availability.

2 package states
Repository candidate not checked

A published vendor fix does not prove that a matching update is enabled and installable on a particular asset. Confirm the local package candidate before scheduling remediation.

Ubuntu releaseSource packageVendor stateFixed versionEvidence
Ubuntu 24.04 LTSnoble · esm-appstomcat10Vendor fix publishedCanonical reports that a fixed source package version has been published. Repository candidate availability is not checked by BlackTree.10.1.16-1ubuntu0.1~esm4Canonical record ↗Source updated 11 Sept 2026
Ubuntu 24.04 LTSnoble · esm-appstomcat9Vendor fix publishedCanonical reports that a fixed source package version has been published. Repository candidate availability is not checked by BlackTree.9.0.70-2ubuntu0.1+esm3Canonical record ↗Source updated 11 Sept 2026
Direct vendor intelligence

Authoritative vendor CSAF and VEX advisories

Structured product status and remediation from the issuing vendor. Product-state explanations are always visible; large lists can be searched or downloaded.

1 current
CVE-2026-43513 · CSAF 2.0 · revision 3 · finalRed Hat Product Securitytomcat-catalina: Apache Tomcat: Improper Handling of Case Sensitivity in LockOutRealm
64 known affected

The vendor explicitly identifies these products as affected by this CVE.

  • tomcat as a component of Red Hat Enterprise Linux 10
  • tomcat-admin-webapps as a component of Red Hat Enterprise Linux 10
  • tomcat-docs-webapp as a component of Red Hat Enterprise Linux 10
  • tomcat-el-5.0-api as a component of Red Hat Enterprise Linux 10
  • tomcat-jsp-3.1-api as a component of Red Hat Enterprise Linux 10
  • tomcat-lib as a component of Red Hat Enterprise Linux 10
  • tomcat-servlet-6.0-api as a component of Red Hat Enterprise Linux 10
  • tomcat-webapps as a component of Red Hat Enterprise Linux 10
  • tomcat.src as a component of Red Hat Enterprise Linux 10
  • tomcat9 as a component of Red Hat Enterprise Linux 10
  • tomcat9-admin-webapps as a component of Red Hat Enterprise Linux 10
  • tomcat9-docs-webapp as a component of Red Hat Enterprise Linux 10
Summary
In Apache Tomcat, LockOutRealm mishandled case sensitivity in usernames, resulting in less effective blocking of brute force attacks.
Remediation
Before applying this update, make sure all previously released errata relevant to your system have been applied. For details on how to apply this update, refer to: https://access.redhat.com/articles/11258
Optional official sources

National CERT insights
?CERT means Computer Emergency Response Team; CSIRT is the closely related term Computer Security Incident Response Team.

Select the national-authority views to include. The exact source language is shown on each matched advisory. Your choice is remembered on this device and encoded in the shareable URL.

Official European source

ENISA European Vulnerability Database

Official EUVD identifiers, advisory evidence and known-exploited context. Missing fields are not treated as evidence of low risk.

1 current
ENISA EUVD identifier

EUVD-2026-29517

No EUVD known-exploited evidence

ENISA has published the identifier mapping but no EUVD description has been stored yet.

EUVD state
Present in the current official mapping
Known exploitation
Not present in the current ENISA EUVD known-exploited dataset. This is not proof of no exploitation.
ENISA score
Not supplied in the stored EUVD record
Advisory evidence
No linked advisory details stored yet
Recommended actionWithin 7 days

High technical severity; prioritise exposed affected systems while verifying vendor guidance.

Patch available
01

What, why and how

Improper Handling of Case Sensitivity vulnerability in LockOutRealm in Apache Tomcat. This issue affects Apache Tomcat: from 11.0.0-M1 through 11.0.21, from 10.1.0-M1 through 10.1.54, from 9.0.0.M1 through 9.0.117, from 8.5.0 through 8.5.100, from 7.0.0 through 7.0.109. Older unsupported versions may also be affected. Users are recommended to upgrade to version 11.0.22, 10.1.55 or 9.0.118 which fix the issue.

What

Improper Handling of Case Sensitivity vulnerability in LockOutRealm in Apache Tomcat. This issue affects Apache Tomcat: from 11.0.0-M1 through 11.0.21, from 10.1.0-M1 through 10.1.54, from 9.0.0.M1 through 9.0.117, from 8.5.0 through 8.5.100, from 7.0.0 through 7.0.109. Older unsupported versions may also be affected. Users are recommended to upgrade to version 11.0.22, 10.1.55 or 9.0.118 which fix the issue.

Why

The product does not properly account for differences in case sensitivity when accessing or determining the properties of a resource, leading to inconsistent results.

How

An attacker operating through a network path may attempt exploitation without authentication or user interaction. If successful, the issue may cause the confidentiality, integrity or availability impact described by the vendor.

What

Improper Handling of Case Sensitivity vulnerability in LockOutRealm in Apache Tomcat. This issue affects Apache Tomcat: from 11.0.0-M1 through 11.0.21, from 10.1.0-M1 through 10.1.54, from 9.0.0.M1 through 9.0.117, from 8.5.0 through 8.5.100, from 7.0.0 through 7.0.109. Older unsupported versions may also be affected. Users are recommended to upgrade to version 11.0.22, 10.1.55 or 9.0.118 which fix the issue.

Why

The product does not properly account for differences in case sensitivity when accessing or determining the properties of a resource, leading to inconsistent results.

How

An attacker operating through a network path may attempt exploitation without authentication or user interaction. If successful, the issue may cause the confidentiality, integrity or availability impact described by the vendor.

02

Exploit reality and attack path

CVSS severity, EPSS forecast probability, public exploit material and CISA-confirmed exploitation are separate signals.

Observed exploitation
?Confirmed exploitation and public exploit material are separate signals. Attacks can occur without public proof-of-concept or exploit code.
No confirmed evidence

No CISA KEV match was present at the last successful refresh. This means no confirmation from that source, not proof of no exploitation.

Public PoC / exploit material
?Confirmed exploitation and public exploit material are separate signals. Attacks can occur without public proof-of-concept or exploit code.
None recorded

No exploit-tagged reference or CISA SSVC proof-of-concept state is currently recorded. Research may still exist outside the structured feeds.

Likely attack path
a network path → Improper Handling of Case Sensitivity → cause the confidentiality, integrity or availability impact described by the vendor
Attack surface
Network
Privileges required
None: unauthenticated exploitation is possible
User interaction
None
Attack complexity
Low: no specialised conditions are recorded
Security boundary
Unchanged: impact remains within the vulnerable component's security authority
Weakness
?CWE means Common Weakness Enumeration: a standard category for the underlying weakness.
CWE-178 ↗

CWE-178: Improper Handling of Case Sensitivity. The product does not properly account for differences in case sensitivity when accessing or determining the properties of a resource, leading to inconsistent results.

CVSS vector
?CVSS means Common Vulnerability Scoring System. The vector records the metric values used to calculate technical severity.
CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:H/I:N/A:N

Common Vulnerability Scoring System 3.1: the compact vector below is decoded into plain language.

AVNetworkAttack vector: The vulnerable component can be reached over a network.ACLowAttack complexity: No specialised conditions are required beyond attacker-controlled input.PRNonePrivileges required: The attacker does not need an account or existing privileges.UINoneUser interaction: No action by another user is required.SUnchangedScope: The security impact remains within the vulnerable component's authority.CHighConfidentiality impact: A successful attack can cause a major loss.INoneIntegrity impact: No direct loss is represented by this metric.ANoneAvailability impact: No direct loss is represented by this metric.
Post-exploitation / living off the land
No specific living-off-the-land technique is confirmed in the structured sources. Monitor normal administration tools for activity inconsistent with the affected service's baseline.
NetworkUnauthenticatedCWE-178
A

Official authority intelligence

Only matched European and national findings are included. Language selectors and unavailable sources are omitted.

BSI · German · WID-SEC-2026-2923Atlassian Produkte (Bamboo, Bitbucket, Confluence, Crucible, Fisheye, und Jira): Mehrere Schwachstellen

Ein Angreifer kann mehrere Schwachstellen in Atlassian Bamboo, Atlassian Bitbucket, Atlassian Confluence, Atlassian Crucible, Atlassian Fisheye und Atlassian Jira ausnutzen, um beliebigen Programmcode auszuführen, um einen Denial of Service Angriff durchzuführen, um Informationen offenzulegen, um Dateien zu manipulieren, um einen Cross-Site Scripting Angriff durchzuführen, um einen SQL-Injection Angriff durchzuführen, und um Sicherheitsvorkehrungen zu umgehen.

Official advisory ↗
BSI · German · WID-SEC-2026-2455Oracle Solaris Drittanbieterkomponenten: Mehrere Schwachstellen

Ein entfernter, anonymer oder authentisierter Angreifer kann mehrere Schwachstellen in verschiedenen Komponenten von Drittanbietern in Oracle Solaris ausnutzen, um einen nicht näher spezifizierten Angriff durchzuführen.

Official advisory ↗
BSI · German · WID-SEC-2026-1955Atlassian Bamboo, Bitbucket, Confluence, Fisheye, Crucible, Jira und Jira Service Management: Mehrere Schwachstellen

Ein Angreifer kann mehrere Schwachstellen in Atlassian Bamboo, Bitbucket, Confluence, Fisheye, Crucible, Jira und Jira Service Management ausnutzen, um beliebigen Code auszuführen, erweiterte Berechtigungen zu erlangen, Sicherheitsmaßnahmen zu umgehen, Daten zu manipulieren, vertrauliche Informationen offenzulegen oder einen Denial-of-Service-Zustand auszulösen.

Official advisory ↗
BSI · German · WID-SEC-2026-1514Apache Tomcat: Mehrere Schwachstellen

Ein Angreifer kann mehrere Schwachstellen in Apache Tomcat ausnutzen, um Sicherheitsmaßnahmen zu umgehen, vertrauliche Informationen offenzulegen, Daten zu manipulieren, einen Denial-of-Service-Zustand herbeizuführen oder andere, nicht spezifizierte bezeichnete Angriffe durchzuführen.

Official advisory ↗
CERT-FR · French · CERTFR-2026-AVI-1165Multiples vulnérabilités dans les produits IBM

d?id=CVE-2026-42580 Référence CVE CVE-2026-42581 https://www.cve.org/CVERecord?id=CVE-2026-42581 Référence CVE CVE-2026-42584 https://www.cve.org/CVERecord?id=CVE-2026-42584 Référence CVE CVE-2026-42585 https://www.cve.org/CVERecord?id=CVE-2026-42585 Référence CVE CVE-2026-42586 https://www.cve.org/CVERecord?id=CVE-2026-42586 Référence CVE CVE-2026-42587 https://www.cve.org/CVERecord?id=CVE-2026-42587 Référence CVE CVE-2026-42778 https://www.cve.org/CVERecord?id=CVE-2026-42778 Référence CVE CVE-2026-42779 https://www.cve.org/CVERecord?id=CVE-2026-42779 Référence CVE CVE-2026-43512 https://www.cve.org/CVERecord?id=CVE-2026-43512 Référence CVE CVE-2026-43513 https://www.cve.org/CVERecord?id=CVE-2026-43513 Référence CVE CVE-2026-43514 https://www.cve.org/CVERecord?id=CVE-2026-43514 Référence CVE CVE-2026-43515 https://www.cve.org/CVERecord?id=CVE-2026-43515 Référence CVE CVE-2026-43827 https://www.cve.org/CVERecord?id=CVE-2026-43827 Référence CVE CVE-2026-43828 https://www.cve.org/CVERecord?id=CVE-2026-43828 Référence CVE CVE-2026-43868 https://www.cve.org/CVERecord?id=CVE-2026-43868 Référence CVE CVE-2026-4410 https://www.cve.org/CVERecord?id=CVE-2026-4410 Référence CVE CVE-2026-44248 https://www.cve.org/CVERecord?id=CVE-2026-44248 Référence CVE CVE-2026-44249 https://www.cve.org/CVERecord?id=CV

Official advisory ↗
CERT-FR · French · CERTFR-2026-AVI-0986Multiples vulnérabilités dans les produits IBM

d?id=CVE-2026-43038 Référence CVE CVE-2026-43051 https://www.cve.org/CVERecord?id=CVE-2026-43051 Référence CVE CVE-2026-43110 https://www.cve.org/CVERecord?id=CVE-2026-43110 Référence CVE CVE-2026-43125 https://www.cve.org/CVERecord?id=CVE-2026-43125 Référence CVE CVE-2026-43158 https://www.cve.org/CVERecord?id=CVE-2026-43158 Référence CVE CVE-2026-43163 https://www.cve.org/CVERecord?id=CVE-2026-43163 Référence CVE CVE-2026-43190 https://www.cve.org/CVERecord?id=CVE-2026-43190 Référence CVE CVE-2026-43329 https://www.cve.org/CVERecord?id=CVE-2026-43329 Référence CVE CVE-2026-43512 https://www.cve.org/CVERecord?id=CVE-2026-43512 Référence CVE CVE-2026-43513 https://www.cve.org/CVERecord?id=CVE-2026-43513 Référence CVE CVE-2026-43514 https://www.cve.org/CVERecord?id=CVE-2026-43514 Référence CVE CVE-2026-43515 https://www.cve.org/CVERecord?id=CVE-2026-43515 Référence CVE CVE-2026-43618 https://www.cve.org/CVERecord?id=CVE-2026-43618 Référence CVE CVE-2026-43964 https://www.cve.org/CVERecord?id=CVE-2026-43964 Référence CVE CVE-2026-4408 https://www.cve.org/CVERecord?id=CVE-2026-4408 Référence CVE CVE-2026-4480 https://www.cve.org/CVERecord?id=CVE-2026-4480 Référence CVE CVE-2026-45186 https://www.cve.org/CVERecord?id=CVE-2026-45186 Référence CVE CVE-2026-45447 https://www.cve.org/CVERecord?id=CVE-

Official advisory ↗
CERT-FR · French · CERTFR-2026-AVI-0773Multiples vulnérabilités dans les produits Atlassian

d?id=CVE-2026-42264 Référence CVE CVE-2026-42342 https://www.cve.org/CVERecord?id=CVE-2026-42342 Référence CVE CVE-2026-42498 https://www.cve.org/CVERecord?id=CVE-2026-42498 Référence CVE CVE-2026-42579 https://www.cve.org/CVERecord?id=CVE-2026-42579 Référence CVE CVE-2026-42583 https://www.cve.org/CVERecord?id=CVE-2026-42583 Référence CVE CVE-2026-42584 https://www.cve.org/CVERecord?id=CVE-2026-42584 Référence CVE CVE-2026-42585 https://www.cve.org/CVERecord?id=CVE-2026-42585 Référence CVE CVE-2026-42587 https://www.cve.org/CVERecord?id=CVE-2026-42587 Référence CVE CVE-2026-43512 https://www.cve.org/CVERecord?id=CVE-2026-43512 Référence CVE CVE-2026-43513 https://www.cve.org/CVERecord?id=CVE-2026-43513 Référence CVE CVE-2026-43515 https://www.cve.org/CVERecord?id=CVE-2026-43515 Référence CVE CVE-2026-44495 https://www.cve.org/CVERecord?id=CVE-2026-44495 Référence CVE CVE-2026-45149 https://www.cve.org/CVERecord?id=CVE-2026-45149 Référence CVE CVE-2026-45736 https://www.cve.org/CVERecord?id=CVE-2026-45736 Gestion détaillée du document le 18 juin 2026 Version initiale Alertes Avis Bulletins d’actualités Mentions légales Conditions générales À propos Contact cyber.gouv.fr service-public.fr legifrance.gouv.fr info.gouv.fr france.fr info.gouv.fr/risques Premier Ministre / Secrétariat Général de la

Official advisory ↗
CERT-FR · French · CERTFR-2026-AVI-0577Multiples vulnérabilités dans Apache Tomcat

De multiples vulnérabilités ont été découvertes dans Apache Tomcat. Elles permettent à un attaquant de provoquer une atteinte à la confidentialité des données, un contournement de la politique de sécurité et un problème de sécurité non spécifié par l'éditeur.

Official advisory ↗
JVN iPedia · Japanese · JVNDB-2026-015820Apache Software FoundationのApache Tomcatにおける大文字と小文字の区別の不適切な処理に関する脆弱性

Apache TomcatのLockOutRealmにおける大文字小文字の区別の不適切な処理に脆弱性があります。この問題は、Apache Tomcatのバージョン11.0.0-M1から11.0.21まで、10.1.0-M1から10.1.54まで、9.0.0-M1から9.0.117まで、8.5.0から8.5.100まで、7.0.0から7.0.109までに影響します。サポートされていない古いバージョンも影響を受ける可能性があります。ユーザーは、この問題を修正したバージョン11.0.22、10.1.55、または9.0.118にアップグレードすることを推奨します。

Official advisory ↗
NCSC-NL · Dutch · NCSC-2026-0325Kwetsbaarheden verholpen in Atlassian producten

Apache Tomcat versions 7.0.0 to 11.0.21 contain multiple security vulnerabilities including LockOutRealm case sensitivity issues, digest authentication bypass, WebDAV request size DoS, HTTP/2 header validation flaws, WebSocket authentication exposure, and AJP secret comparison weaknesses.

Official advisory ↗
03

Patch and workaround

Operational remediation based on structured source evidence.

Status
?Patch availability is based on structured fixed-version fields and authoritative update references. If no fix is verified, check the vendor advisory before making a change.
Patch available
Affected
Fixed
Action
Before applying this update, make sure all previously released errata relevant to your system have been applied. For details on how to apply this update, refer to: https://access.redhat.com/articles/11258
Workaround
No verified workaround is recorded. If business-safe, reduce exposure to the affected interface and allow only trusted sources until authoritative guidance is available.
04

Evidence and provenance

Published 12 May 2026 · Last source change 14 May 2026, 19:53 UTC · CWE-178 · Improper Handling of Case Sensitivity

CVE recordCVE.org · 5.2
CVSS sourceCISA ADP
EPSS source
?The date BlackTree first stored a score for this CVE from the daily FIRST EPSS feed.
FIRST · tracked since 2026-08-14
European sourceENISA EUVD · EUVD-2026-29517
Product sourceVendor CSAF · Red Hat Product Security
Remediation sourceVendor CSAF · Red Hat Product Security
CWE sourceCNA
NVD statusNVD enriched

Core structured fields are present and their contributing authorities are shown above.

Material change intelligence

What changed after publication

View recent updates ↗

No material field changes have been recorded since change tracking began. Routine source refreshes and cosmetic edits are intentionally excluded.

Material fields only · duplicate refreshes suppressed · history retained for the configured operational retention period
CVE published
ENISA EUVD · EUVD-2026-29517↗Vendor CSAF · Red Hat Product Security↗CVE authority or vendor reference↗Official CVE record (CNA and ADP data)↗NVD record↗
Technical terms and abbreviations used in this report
CVE
Common Vulnerabilities and Exposures: the public identifier for one disclosed vulnerability.
CVSS
Common Vulnerability Scoring System: a technical severity framework; it is not patching priority by itself.
EPSS
Exploit Prediction Scoring System: FIRST's estimate of the probability that exploitation activity will be observed in the next 30 days; it is a forecast, not confirmation.
CWE
Common Weakness Enumeration: the standard category describing the underlying software or hardware weakness.
CNA
CVE Numbering Authority: an organisation authorised to assign and publish CVE records.
CISA ADP
Cybersecurity and Infrastructure Security Agency Authorized Data Publisher: structured enrichment added to a CVE record.
NVD
National Vulnerability Database: NIST's enrichment service for CVE records.
CERT / CSIRT
A computer security incident response team that publishes warnings or coordinates incident response.
PoC
Proof of concept: public material that demonstrates or helps reproduce exploitation.
CSAF
Common Security Advisory Framework: a machine-readable format for security advisories.
LoTL
Living off the land: abuse of legitimate tools or system functions during an attack.
Free version - for non-commercial use only.CVE-2026-43513 · cve.blacktree.nl