Cyber Resilience

CVE-2026-34483

Apache Tomcat 9.0.40 – 9.0.117

Published
09 April 2026
Modified
14 April 2026
Patch / advisory
View advisory
CVSS Score v3.1 7.5
Click a component to see what it means
Raw vectorCVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:H/I:N/A:N
EPSS Score 0.0046 38th percentile
Risk Priority 57 floored blend · peak EPSS

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 Content Injection (T1659); ranked at the 38th percentile by exploit likelihood (below the median); it is not currently listed in the CISA KEV catalog.

Deeper analysis AI-assisted summary

Synthesised by an AI model from the NVD description and linked references — a reading aid, not an authoritative source.

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).

OWASP Top 10 for Web (2025)

A05:2025 Injection

EU & UK References

Vulnerability Data

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 Techniques

T1659 Content Injection Initial Access
Adversaries may gain access and continuously communicate with victims by injecting malicious content into systems through online network traffic.
attack.mitre.org →
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 →
T1059 Command and Scripting Interpreter Execution
Adversaries may abuse command and script interpreters to execute commands, scripts, or binaries.
attack.mitre.org →
T1203 Exploitation for Client Execution Execution
Adversaries may exploit software vulnerabilities in client applications to execute code.
attack.mitre.org →
Derived from this CVE’s CWE(s) via the direct CWE→ATT&CK cross-walk.

CVEs Like This One

CVE-2025-31651Same product: Apache Tomcat
CVE-2025-52520Same product: Apache Tomcat
CVE-2026-41293Same product: Apache Tomcat
CVE-2026-24733Same product: Apache Tomcat
CVE-2026-32990Same product: Apache Tomcat
CVE-2026-55957Same product: Apache Tomcat
CVE-2026-59083Same product: Apache Tomcat
CVE-2026-24880Same product: Apache Tomcat
CVE-2025-55754Same product: Apache Tomcat
CVE-2023-46589Same 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

Control response

Prevent
Stop it (NIST 800-53)

—

Detect
Catch it (NIST detect / respond)

—

Harden
Shrink the surface (DISA STIG)

—

Validate
Prove the fix (OWASP ASVS)
  • V1.1.2
  • V1.2.1
  • V1.2.3

Likely Mitigating Controls AI

Per-CVE control mapping for this CVE has not run yet; the list below is derived from the weakness types (CWEs) cited in the NVD entry.

SI-15 Information Output Filtering
addresses: CWE-116

Validating that output matches expected content directly mitigates failures to properly encode or escape data for its destination context.

Mitigating Controls (NIST CSF 2.0) AI

Derived directly from the weakness types (CWEs) cited in the NVD entry via our AI-authored CWE→CSF cross-walk (authority under review) — links open the control.

PR.PS-06 mostly match
prevents

Secure SDLC practices directly require proper output encoding to prevent injection and message malformation.

Mitigating Controls (ISO/IEC 27001:2022 Annex A) AI

Derived directly from the weakness types (CWEs) cited in the NVD entry via our AI-authored CWE→ISO cross-walk (authority under review) — links open the control.

A.8.28 Secure coding mostly match
prevents

Secure coding standards explicitly require correct output encoding and escaping to preserve message structure.

A.8.29 Security testing in development and acceptance mostly match
finds

Security testing can detect missing or incorrect encoding but does not itself implement the control.

A.8.25 Secure development life cycle partial match
prevents

Secure development life cycle mandates output encoding/escaping practices that directly prevent improper encoding.

A.8.26 Application security requirements partial match
prevents

Application security requirements include explicit rules for safe output handling and encoding.

A.8.27 Secure system architecture and engineering principles partial match
prevents

Secure architecture principles reduce the likelihood of missing encoding but do not prescribe the actual technique.

References