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HIGH severity

CVE-2026-42498 — tomcat-embed-core

HIGHFix: apache/tomcat@169d725

CVE-2026-42498 is a high-severity (CVSS 7.3) Information Exposure vulnerability in org.apache.tomcat.embed:tomcat-embed-core. A fix is available for org.apache.tomcat.embed:tomcat-embed-core — see the affected versions and patch details below.

Apache Tomcat: WebSocket authentication header exposure

Also known asBIT-tomcat-2026-42498GHSA-fv25-8xcx-gqjc
Published
Updated
Affected
9 pkgs
Patched
9 / 9
Exploits
None indexed
Exploitation data as of Nov 10, 2026 · OSV.dev, NVD, FIRST.org (EPSS)

Exploitation Status

No confirmed exploitation observed yet

  • CISA assesses this as automatable — exploitation doesn’t require manual, per-target effort, which raises the odds of mass scanning and opportunistic attacks.
  • CISA’s own triage has not observed active exploitation or public proof-of-concept code for this CVE as of its last assessment.

Exploitation and automatability from CISA’s SSVC triage for CVE-2026-42498.

EPSS Exploitation Probability

via FIRST.org ↗
0.7%probability of exploitation in next 30 days
Lower Risk+0.05%
Lower risk than most CVEs53th percentile — riskier than 53% of all scored CVEsHighest risk
0.00%0.40%0.79%1.19%0.1%0.7%Jun 26Sep 26Nov 26

Probability of exploitation in the next 30 days, from FIRST.org EPSS.

How urgent is this, really

Where this sits among everything scored

Real-World Exposure

9 pkgs affected
☕org.apache.tomcat.embed:tomcat-embed-core☕org.apache.tomcat.embed:tomcat-embed-core☕org.apache.tomcat.embed:tomcat-embed-core☕org.apache.tomcat:tomcat☕org.apache.tomcat:tomcat☕org.apache.tomcat:tomcat☕org.apache.tomcat:tomcat-catalina☕org.apache.tomcat:tomcat-catalina+1 more

Real-time download stats are indexed for npm and PyPI packages. This vulnerability affects Maven packages — download data is not available via public APIs for these ecosystems.

Description

Versions Affected: Apache Tomcat 11.0.0-M1 to 11.0.21 Apache Tomcat 10.1.0-M1 to 10.1.54 Apache Tomcat 9.0.2 to 9.0.117 Older, unsupported versions may also be affected

Description: If a WebSocket request was redirected after authentication, Tomcat's WebSocket client would present the most recent authentication header to the redirect target host.

Mitigation: Users of the affected versions should apply one of the following mitigations:

  • Upgrade to Apache Tomcat 11.0.22 or later
  • Upgrade to Apache Tomcat 10.1.55 or later
  • Upgrade to Apache Tomcat 9.0.118 or later

Credit: This issue was identified by lokerxx

Affected Packages

9 total 9 fixed
EcosystemPackageVulnerable rangeFix
☕Mavenorg.apache.tomcat.embed:tomcat-embed-coreall versions9.0.118org.apache.tomcat.embed:tomcat-embed-core:9.0.118
☕Mavenorg.apache.tomcat.embed:tomcat-embed-core≥ 10.1.0-M1&&< 10.1.5510.1.55org.apache.tomcat.embed:tomcat-embed-core:10.1.55
☕Mavenorg.apache.tomcat.embed:tomcat-embed-core≥ 11.0.0-M1&&< 11.0.2211.0.22org.apache.tomcat.embed:tomcat-embed-core:11.0.22
☕Mavenorg.apache.tomcat:tomcatall versions9.0.118org.apache.tomcat:tomcat:9.0.118
☕Mavenorg.apache.tomcat:tomcat≥ 10.1.0-M1&&< 10.1.5510.1.55org.apache.tomcat:tomcat:10.1.55
☕Mavenorg.apache.tomcat:tomcat≥ 11.0.0-M1&&< 11.0.2211.0.22org.apache.tomcat:tomcat:11.0.22

Affected Products

1 product · 5 configurations
Application
tomcatapache
≥ 11.0.0 && ≤ 8.5.100
range

Detection & mitigation playbook

Open-source dependency

  1. Detect

    Scan your dependency tree (package-lock.json, pnpm-lock.yaml, requirements.txt, go.sum, etc.) for org.apache.tomcat.embed:tomcat-embed-core, including transitive dependencies — a direct dependency you never call can still pull in a vulnerable version.

  2. Fix

    Update org.apache.tomcat.embed:tomcat-embed-core to 9.0.118 or later, then make sure no transitive (indirect) dependency still pins the vulnerable range — O3 confirms CVE-2026-42498 is resolved across your whole dependency graph.

  3. Workarounds

    Assume what was exposed is already known: rotate any credential, token or key that the affected component could return, restrict the endpoint to callers that genuinely need it, and strip sensitive fields from responses and error output at the boundary rather than relying on the client not to read them.

Fixing This On Your OS

If you run this on a Linux distribution, patch through your package manager against the distro's own security advisory below — it tracks the exact backported fix for your release, which can ship on a different timeline (and sometimes a different severity) than the upstream project.

Red HatModerate
ProductFixed inAdvisory
Red Hat Enterprise Linux 10tomcat9-1:9.0.120-1.el10_2RHSA-2026:68651
Red Hat Enterprise Linux 10tomcat-1:10.1.49-4.el10_2RHSA-2026:69259
Red Hat Enterprise Linux 10.0 Extended Update Supporttomcat9-1:9.0.120-1.el10_0RHSA-2026:67163
Red Hat Enterprise Linux 10.0 Extended Update Supporttomcat-1:10.1.49-1.el10_0RHSA-2026:67164
Red Hat Enterprise Linux 8tomcat-1:9.0.120-1.el8_10RHSA-2026:68677
Red Hat Enterprise Linux 8.8 Telecommunications Update Servicetomcat-1:9.0.120-1.el8_8RHSA-2026:68680
Red Hat Enterprise Linux 9tomcat-1:9.0.120-2.el9_8RHSA-2026:68660
Red Hat Enterprise Linux 9.2 Update Services for SAP Solutionstomcat-1:9.0.120-1.el9_2RHSA-2026:68678
UbuntuHIGH
USN-8417-1UbuntuUSN-8450-1Ubuntu

Frequently Asked Questions

Versions Affected: Apache Tomcat 11.0.0-M1 to 11.0.21 Apache Tomcat 10.1.0-M1 to 10.1.54 Apache Tomcat 9.0.2 to 9.0.117 Older, unsupported versions may also be affected Description: If a WebSocket request was redirected after authentication, Tomcat's WebSocket client would present the most recent authentication header to the redirect target host. Mitigation: Users of the affected versions should apply one of the following mitigations: - Upgrade to Apache Tomcat 11.0.22 or later - Upgrade to Apache Tomcat 10.1.55 or later - Upgrade to Apache Tomcat 9.0.118 or later Credit: This issue was ide
O3 Security · Impact-Aware SCA

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CVE-2026-42498: tomcat-embed-core — Fixed in 9.0.118