Cyber Resilience

CVE-2026-34483

High

Published: 09 April 2026

Published
09 April 2026
Modified
14 April 2026
KEV Added
—
Patch
—
CVSS Score v3.1 7.5 CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:H/I:N/A:N
EPSS Score 0.0007 21.0th percentile
Risk Priority 15 60% EPSS · 20% KEV · 20% CVSS

Summary

CVE-2026-34483 is a high-severity Improper Encoding or Escaping of Output (CWE-116) vulnerability in Apache Tomcat. Its CVSS base score is 7.5 (High).

Operationally, exploitation aligns with the MITRE ATT&CK technique Exploit Public-Facing Application (T1190); ranked at the 21.0th percentile by exploit likelihood (below the median); it is not currently listed in the CISA KEV catalog.

The strongest mitigations our analysis identified are NIST 800-53 SI-15 (Information Output Filtering) and SI-2 (Flaw Remediation).

Deeper analysis

CVE-2026-34483 is an Improper Encoding or Escaping of Output vulnerability (CWE-116) in the JsonAccessLogValve component of Apache Tomcat. It affects Apache Tomcat versions from 11.0.0-M1 through 11.0.20, 10.1.0-M1 through 10.1.53, and 9.0.40 through 9.0.116. The vulnerability has a CVSS v3.1 base score of 7.5 (AV:N/AC:L/PR:N/UI:N/S:U/C:H/I:N/A:N), indicating high severity primarily due to confidentiality impact.

An unauthenticated attacker with network access can exploit this vulnerability with low complexity and no user interaction required. Successful exploitation allows disclosure of sensitive information, as the improper encoding or escaping in the JsonAccessLogValve enables attackers to extract confidential data from the system.

Apache advisories recommend upgrading to mitigated versions: 11.0.21, 10.1.54, or 9.0.117, which address the issue. Further details are available in the Apache Tomcat announcement on their mailing list (https://lists.apache.org/thread/j1w7304yonlr8vo1tkb5nfs7od1y228b) and the oss-security mailing list (http://www.openwall.com/lists/oss-security/2026/04/09/26).

EU & UK References

Vulnerability details

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…

more

or 9.0.117 , which fix the issue.

CWE(s)
CWE-116

Related Threats

MITRE ATT&CK Enterprise TechniquesAI

T1190 Exploit Public-Facing Application Initial Access
Adversaries may attempt to exploit a weakness in an Internet-facing host or system to initially access a network.
attack.mitre.org →
Why these techniques?

The CVE describes a remote unauthenticated network-accessible vulnerability in the public-facing JsonAccessLogValve of Apache Tomcat that directly enables exploitation for sensitive information disclosure.

Confidence: HIGH · MITRE ATT&CK Enterprise v18.1

CVEs Like This One

CVE-2026-34486Same product: Apache Tomcat
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CVE-2026-29146Same product: Apache Tomcat
CVE-2025-66614Same product: Apache Tomcat
CVE-2025-55754Same product: Apache Tomcat
CVE-2026-41293Same product: Apache Tomcat
CVE-2026-29129Same product: Apache Tomcat
CVE-2026-41284Same product: Apache Tomcat

Affected Assets

apache
tomcat
9.0.40 — 9.0.117 · 10.1.0 — 10.1.54 · 11.0.0 — 11.0.21

Mitigating Controls

Mitigating Controls (NIST 800-53 r5) AI

SI-2 Flaw Remediation good match
prevent

Directly remediates the improper encoding vulnerability in Apache Tomcat's JsonAccessLogValve through timely application of vendor patches and upgrades.

SI-15 Information Output Filtering good match
prevent

Mandates filtering and proper encoding of output information, countering the CWE-116 improper escaping in JSON access log output that enables sensitive data disclosure.

AU-9 Protection of Audit Information partial match
prevent

Protects audit records generated by JsonAccessLogValve from unauthorized access and disclosure, mitigating exploitation of the encoding flaw.

References