CVE-2026-55276 is a critical-severity (CVSS 9.1) CWE-670 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: Logged effective web.xml is incomplete
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.
- A successful exploit gives an attacker total control of the affected component, not partial access.
- 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-2026-55276.
EPSS Exploitation Probability
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
org.apache.tomcat.embed:tomcat-embed-core☕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+4 moreReal-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
Always-Incorrect Control Flow Implementation vulnerability in Apache Tomcat meant that special roles and empty authorisation constraints were not included when the effective web.xml was logged.
This issue affects Apache Tomcat: from 11.0.0-M1 through 11.0.22, from 10.1.0-M1 through 10.1.55, from 9.0.0.M1 through 9.0.118, 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 11.0.23, 10.1.56 or 9.0.119 which fixes the issue.
Affected Packages
| Ecosystem | Package | Vulnerable range | Fix |
|---|---|---|---|
| ☕Maven | org.apache.tomcat.embed:tomcat-embed-core | ≥ 11.0.0-M1&&< 11.0.23 | 11.0.23org.apache.tomcat.embed:tomcat-embed-core:11.0.23 |
| ☕Maven | org.apache.tomcat.embed:tomcat-embed-core | ≥ 10.1.0-M1&&< 10.1.56 | 10.1.56org.apache.tomcat.embed:tomcat-embed-core:10.1.56 |
| ☕Maven | org.apache.tomcat.embed:tomcat-embed-core | ≥ 9.0.0.M1&&< 9.0.119 | 9.0.119org.apache.tomcat.embed:tomcat-embed-core:9.0.119 |
| ☕Maven | org.apache.tomcat.embed:tomcat-embed-core | ≥ 8.5.0 | No fix |
| ☕Maven | org.apache.tomcat:tomcat | ≥ 11.0.0-M1&&< 11.0.23 | 11.0.23org.apache.tomcat:tomcat:11.0.23 |
| ☕Maven | org.apache.tomcat:tomcat | ≥ 10.1.0-M1&&< 10.1.56 | 10.1.56org.apache.tomcat:tomcat:10.1.56 |
Affected Products
tomcatapacheDetection & mitigation playbook
Open-source dependencyDetect
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.
Fix
Update org.apache.tomcat.embed:tomcat-embed-core to 11.0.23 or later, then make sure no transitive (indirect) dependency still pins the vulnerable range — O3 confirms CVE-2026-55276 is resolved across your whole dependency graph.
Workarounds
If you can't upgrade right away: gate or disable the affected feature, validate untrusted input at the boundary, and avoid passing attacker-controlled data into the vulnerable path. O3's runtime protection blocks exploitation in production as an interim safeguard until the upgrade lands.
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.
A flaw was found in Apache Tomcat. When the effective web.xml logging feature is enabled for debugging, special roles and empty authorization constraints may be omitted from the logged output. This is a logging-only issue with no runtime security impact — it only affects the accuracy of debug log output for…
This is a logging-only issue with no runtime security impact. No mitigation is required. Administrators should not rely solely on the effective web.xml debug log output to verify security constraint configuration.Source: Red Hat security advisory for CVE-2026-55276 (CC BY 4.0)
| Product | Fixed in | Advisory |
|---|---|---|
| Red Hat Enterprise Linux 10 | tomcat9-1:9.0.120-1.el10_2 | RHSA-2026:68651 |
| Red Hat Enterprise Linux 10.0 Extended Update Support | tomcat9-1:9.0.120-1.el10_0 | RHSA-2026:67163 |
| Red Hat Enterprise Linux 8 | tomcat-1:9.0.120-1.el8_10 | RHSA-2026:68677 |
| Red Hat Enterprise Linux 8.8 Telecommunications Update Service | tomcat-1:9.0.120-1.el8_8 | RHSA-2026:68680 |
| Red Hat Enterprise Linux 9 | tomcat-1:9.0.120-2.el9_8 | RHSA-2026:68660 |
| Red Hat Enterprise Linux 9.2 Update Services for SAP Solutions | tomcat-1:9.0.120-1.el9_2 | RHSA-2026:68678 |
| Red Hat Enterprise Linux 9.4 Update Services for SAP Solutions | tomcat-1:9.0.120-1.el9_4 | RHSA-2026:68679 |
| Red Hat Enterprise Linux 9.6 Extended Update Support | tomcat-1:9.0.120-1.el9_6 | RHSA-2026:68659 |
Frequently Asked Questions
Is CVE-2026-55276 in your dependencies?
Find it across Maven, including transitive dependencies.