CVE-2026-34483 — tomcat-catalina
HIGHCVE-2026-34483 is a high-severity (CVSS 7.5) CWE-116 vulnerability in org.apache.tomcat:tomcat-catalina. A fix is available for org.apache.tomcat:tomcat-catalina — see the affected versions and patch details below.
Apache Tomcat: Incomplete escaping of JSON access logs
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-2026-34483.
EPSS Exploitation Probability
EPSS (Exploit Prediction Scoring System) is a daily probability model maintained by FIRST.org. It estimates the likelihood a CVE will be exploited in production environments within the next 30 days, derived from real-world threat intelligence signals.
How urgent is this, really
CVE-2026-34483 plotted by exploitation likelihood (EPSS) against impact (CVSS). The shaded corner — EPSS 50%+ and CVSS 7.0+ — is where this CVE doesn't sit, though severity or exploitability alone can still warrant action.
Where this sits among everything scored
Of 378,567 CVEs with a current EPSS score, this one falls in the < 10% band (highlighted). Real counts from FIRST.org, not a sample — log-scaled since the landscape is heavily right-skewed.
Real-World Exposure
org.apache.tomcat:tomcat-catalina☕org.apache.tomcat:tomcat-catalina☕org.apache.tomcat:tomcat-catalina☕org.apache.tomcat:tomcat☕org.apache.tomcat:tomcat☕org.apache.tomcat:tomcat☕org.apache.tomcat.embed:tomcat-embed-core☕org.apache.tomcat.embed:tomcat-embed-core+1 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
Improper Encoding or Escaping of Output vulnerability in the JsonAccessLogValve component of Apache Tomcat.
This issue affects Apache Tomcat: from 11.0.0-M1 through 11.0.20, from 10.1.0-M1 through 10.1.53, from 9.0.40 through 9.0.116.
Users are recommended to upgrade to version 11.0.21, 10.1.54 or 9.0.117 , which fix the issue.
Affected Packages
| Ecosystem | Package | Vulnerable range | Fix |
|---|---|---|---|
| ☕Maven | org.apache.tomcat:tomcat-catalina | ≥ 9.0.40&&< 9.0.116 | 9.0.116org.apache.tomcat:tomcat-catalina:9.0.116 |
| ☕Maven | org.apache.tomcat:tomcat-catalina | ≥ 10.1.0-M1&&< 10.1.54 | 10.1.54org.apache.tomcat:tomcat-catalina:10.1.54 |
| ☕Maven | org.apache.tomcat:tomcat-catalina | ≥ 11.0.0-M1&&< 11.0.21 | 11.0.21org.apache.tomcat:tomcat-catalina:11.0.21 |
| ☕Maven | org.apache.tomcat:tomcat | ≥ 9.0.40&&< 9.0.116 | 9.0.116org.apache.tomcat:tomcat:9.0.116 |
| ☕Maven | org.apache.tomcat:tomcat | ≥ 10.1.0-M1&&< 10.1.54 | 10.1.54org.apache.tomcat:tomcat:10.1.54 |
| ☕Maven | org.apache.tomcat:tomcat | ≥ 11.0.0-M1&&< 11.0.21 | 11.0.21org.apache.tomcat:tomcat:11.0.21 |
Detection & mitigation playbook
Open-source dependencyDetect
Scan your dependency tree (package-lock.json, pnpm-lock.yaml, requirements.txt, go.sum, etc.) for org.apache.tomcat:tomcat-catalina, including transitive dependencies — a direct dependency you never call can still pull in a vulnerable version.
Fix
Update org.apache.tomcat:tomcat-catalina to 9.0.116 or later, then make sure no transitive (indirect) dependency still pins the vulnerable range — O3 confirms CVE-2026-34483 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.
How O3 protects you
O3 Security's impact-aware SCA analyses which vulnerable code paths your application actually calls, so a match like CVE-2026-34483 can be triaged on real exposure rather than presence alone.
Tailored to CVE-2026-34483. Runtime protection reduces exposure until a permanent patch is applied and verified — it complements patching, it doesn't replace it.
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.
Low impact. A flaw in the Apache Tomcat JsonAccessLogValve component allows for improper encoding of output. This could enable an attacker to inject specially crafted data into log files, potentially leading to information disclosure or other unintended consequences during log processing. This affects Red Hat…
| Product | Fixed in | Advisory |
|---|---|---|
| Red Hat Enterprise Linux 10 | tomcat9-1:9.0.117-2.el10_2 | RHSA-2026:36790 |
| Red Hat JBoss Web Server 6.2.3 | tomcat | RHSA-2026:20406 |
| Red Hat JBoss Web Server 6.2 on RHEL 10 | jws6-tomcat-0:10.1.49-13.redhat_00011.1.el10jws | RHSA-2026:20405 |
Frequently Asked Questions
Is CVE-2026-34483 in your dependencies?
O3 Security finds CVE-2026-34483 across Maven dependencies, including transitive ones, and its impact-aware SCA ranks findings by whether your code actually calls the vulnerable path.