Home/CVE/Improper Encoding or Escaping of Output vulnerability in the JsonAccessLogValve component of Apache Tomcat. This issue
CVE

CVE-2026-34483

Improper Encoding or Escaping of Output vulnerability in the JsonAccessLogValve component of Apache Tomcat. This issue

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.

HIGH · CVSS 7.5 EPSS 0.00067
Schedule remediation
  • SSVC automatable: yes - attacks can be scripted at scale
  • CVSS base score ≥ 7.0
Sigma rules1 YARA rules0
⬡

Weakness Classification

CWE-116Improper Encoding or Escaping of Output
▤

Affected Products & Versions

3
apache tomcat>= 9.0.40 and < 9.0.117
apache tomcat>= 10.1.0 and < 10.1.54
apache tomcat>= 11.0.0 and < 11.0.21
▤

Affected Packages

3
Language-ecosystem packages (from OSV) tied to this CVE, with the version that fixes it - the dependency-level detail NVD doesn’t carry.
Maven org.apache.tomcat.embed:tomcat-embed-core HIGH fixed in 9.0.116
Maven org.apache.tomcat:tomcat HIGH fixed in 9.0.116
Maven org.apache.tomcat:tomcat-catalina HIGH fixed in 9.0.116
◈

Sigma Hunt Rules

1
Exact rules name this CVE ID. Product rules name an affected product in their title. Related rules cover techniques used by actors who exploited this CVE. Showing the most relevant matches; the complete related set is on the full drill-down.
productmediumTomcat WebServer Logs Deleted
▣

Scoring & Timeline

7.5
HIGH · CVSS v3.1 · security@apache.org
View on NVD
Attack Vector
Network Adjacent Local Physical
Attack Complexity
Low High
Privileges Required
None Low High
User Interaction
None Required
Scope
Unchanged Changed
Confidentiality
None Low High
Integrity
None Low High
Availability
None Low High
Published to NVD09 Apr 2026 · 08:16 PM
CVSS VectorCVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:H/I:N/A:N
SSVC triage · cisa-vulnrichment
Exploitation
none
Automatable
yes
Technical impact
partial
SSVC asks the questions that actually drive patch urgency: is it being exploited, can attacks be automated, and how total is the impact.
⚑

Vendor Advisories

16
suse-csafSUSE-SU-2026:1603-1
suse-csafSUSE-SU-2026:1604-1
suse-csafSUSE-SU-2026:1572-1
suse-csafopenSUSE-SU-2026:20611-1
suse-csafopenSUSE-SU-2026:20612-1
🔗

References & Sources

2
Source URLs (vendor pages, mailing lists, write-ups). Exploit/PoC links are in their own section above to avoid duplication.
https://lists.apache.org/thread/j1w7304yonlr8vo1tkb5nfs7od1y228bMailing ListVendor Advisory
http://www.openwall.com/lists/oss-security/2026/04/09/26Mailing ListThird Party Advisory
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