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Medium

Apache Tomcat Denial of Service via Malformed Request Headers

  • Disclosed: 02.05.2022
  • Updated: 11.10.2026 11:21

Apache Tomcat 4.1.0 through 4.1.39, 5.5.0 through 5.5.27, and 6.0.0 through 6.0.18, when the Java AJP connector and mod_jk load balancing are used, allows remote attackers to cause a denial of service (application outage) via a crafted request with invalid headers, related to temporary blocking of connectors that have encountered errors, as demonstrated by an error involving a malformed HTTP Host header.

Affected software

Click a technology to see all vulnerabilities affecting it.

PlatformPackageVulnerable versionsFixed in
Java / Kotlin (Maven) org.apache.tomcat:tomcat >= 4.1.0, <= 4.1.39, >= 5.5.0, <= 5.5.27, >= 6.0.0, <= 6.0.18 no fix

References

CVSS score -
Weakness (CWE)
CWE-20, CWE-400
Platform
Java / Kotlin (Maven)
Package
org.apache.tomcat:tomcat
Disclosed
02.05.2022
Updated
11.10.2026 11:21

Sources and licenses

OSV / GitHub Advisory Database - GHSA-5cw4-ggx9-36vg - CC BY 4.0

Vulnerability history: org.apache.tomcat:tomcat

All published vulnerabilities of this package (Java / Kotlin (Maven)), newest first. Shows whether this is a one-off slip or a package that needs watching.

All (162) in the archive
Total entries
162
First → latest
12.2018 08.2026
Without a fix
20
Exploited in attacks
1

Severity breakdown

  • Critical 8
  • High 40
  • Medium 102
  • Low 12

Disclosures per year

Severity:
  1. Apache Tomcat Denial of Service via Malformed Request Headers this entry
    Medium CVE-2009-0033 >= 4.1.0, <= 4.1.39, >= 5.5.0, <= 5.5.27, >= 6.0.0, <= 6.0.18 no fix
  2. Apache Tomcat's DIGEST authenticator has an Authentication Bypass by Capture-replay vulnerability
    Critical · 9.8 CVE-2026-65905 >= 11.0.0-M1, < 11.0.25, >= 10.1.0-M1, < 10.1.58, >= 9.0.0.M1, < 9.0.121, >= 8.5.0, <= 8.5.100, >= 7.0.30, <= 7.0.109 11.0.25, 10.1.58, 9.0.121
  3. Apache Tomcat has an Improper Access Control, Incorrect Authorization vulnerability
    Critical · 9.1 CVE-2026-65182 >= 11.0.0-M1, < 11.0.25, >= 10.1.0-M1, < 10.1.58, >= 9.0.0-M1, < 9.0.121, >= 8.5.0, <= 8.5.100, >= 7.0.0, <= 7.0.109 11.0.25, 10.1.58, 9.0.121
  4. Apache Tomcat's FORM authentication process has an Incorrect Authorization vulnerability
    Critical · 9.1 CVE-2026-68525 >= 11.0.0-M1, < 11.0.25, >= 10.1.0-M1, < 10.1.58, >= 9.0.0-M1, < 9.0.121, >= 8.5.0, <= 8.5.100, >= 7.0.0, <= 7.0.109 11.0.25, 10.1.58, 9.0.121
  5. Apache Tomcat: Unbounded read in WebDAV LOCK and PROPFIND handling
    High · 7.5 CVE-2026-41284 < 9.0.118, >= 10.1.0-M1, < 10.1.55, >= 11.0.0-M1, < 11.0.22 9.0.118, 10.1.55, 11.0.22
  6. Apache Tomcat - Digest authenticator will authenticate any unknown user
    Critical · 9.8 CVE-2026-43512 < 9.0.118, >= 10.1.0-M1, < 10.1.55, >= 11.0.0-M1, < 11.0.22 9.0.118, 10.1.55, 11.0.22
  7. Apache Tomcat: LockOutRealm treats user names as case-sensitive
    High · 7.5 CVE-2026-43513 < 9.0.118, >= 10.1.0-M1, < 10.1.55, >= 11.0.0-M1, < 11.0.22 9.0.118, 10.1.55, 11.0.22
  8. Apache Tomcat - Security constraints not correctly applied
    Critical · 9.1 CVE-2026-43515 < 9.0.118, >= 10.1.0-M1, < 10.1.55, >= 11.0.0-M1, < 11.0.22 9.0.118, 10.1.55, 11.0.22
  9. Apache Tomcat - WebSocket authentication header exposure
    High · 7.3 CVE-2026-42498 < 9.0.118, >= 10.1.0-M1, < 10.1.55, >= 11.0.0-M1, < 11.0.22 9.0.118, 10.1.55, 11.0.22
  10. Apache Tomcat - HTTP/2 request headers not validated
    Critical · 9.8 CVE-2026-41293 >= 8.5.0, < 9.0.118, >= 10.1.0-M1, < 10.1.55, >= 11.0.0-M1, < 11.0.22 9.0.118, 10.1.55, 11.0.22
  11. Apache Tomcat vulnerable to Insertion of Sensitive Information into Log File
    High · 7.5 CVE-2026-34487 >= 9.0.13, < 9.0.117, >= 10.1.0-M1, < 10.1.54, >= 11.0.0-M1, < 11.0.21 9.0.117, 10.1.54, 11.0.21
  12. Apache Tomcat has an Improper Encoding or Escaping of Output vulnerability in the JsonAccessLogValve
    High · 7.5 CVE-2026-34483 >= 9.0.40, < 9.0.116, >= 10.1.0-M1, < 10.1.54, >= 11.0.0-M1, < 11.0.21 9.0.116, 10.1.54, 11.0.21
  13. Apache Tomcat Missing Encryption of Sensitive Data vulnerability
    High · 7.5 Exploited in attacks CVE-2026-34486 >= 11.0.20, < 11.0.21, >= 10.1.53, < 10.1.54, >= 9.0.116, < 9.0.117 11.0.21, 10.1.54, 9.0.117
  14. Apache Tomcat: Padding Oracle vulnerability in EncryptInterceptor
    High · 7.5 CVE-2026-29146 >= 9.0.13, < 9.0.116, >= 10.1.50, < 10.1.53, >= 11.0.0-M1, < 11.0.20, >= 8.5.38, <= 8.5.100, >= 7.0.100, <= 7.0.109 9.0.116, 10.1.53, 11.0.20
  15. Apache Tomcat: CLIENT_CERT authentication does not fail as expected
    Critical · 9.1 CVE-2026-29145 >= 9.0.83, < 9.0.116, >= 10.1.0-M7, < 10.1.53, >= 11.0.0-M1, < 11.0.20 9.0.116, 10.1.53, 11.0.20
  16. Apache Tomcat: Configured cipher preference order not preserved
    High · 7.5 CVE-2026-29129 >= 9.0.114, < 9.0.116, >= 10.1.51, < 10.1.53, >= 11.0.16, < 11.0.20 9.0.116, 10.1.53, 11.0.20
  17. Apache Tomcat Vulnerable to Relative Path Traversal
    High · 7.5 CVE-2025-55752 >= 11.0.0-M1, < 11.0.11, >= 10.1.0-M1, < 10.1.45, >= 9.0.0-M11, < 9.0.109, >= 8.5.6, <= 8.5.100 11.0.11, 10.1.45, 9.0.109
  18. Deserialization of Untrusted Data in Apache Tomcat
    High CVE-2013-2185 < 7.0.39 7.0.39
  19. Improper Neutralization of Input During Web Page Generation in Apache Tomcat
    High · 8.1 CVE-2015-5346 >= 9.0.0.M1, < 9.0.0.M2, >= 8.0.0.RC1, < 8.0.31, >= 7.0.0, < 7.0.66 9.0.0.M2, 8.0.31, 7.0.66
  20. Apache Tomcat allows remote attackers to bypass a CSRF protection mechanism by using a token
    High · 8.8 CVE-2015-5351 < 7.0.68, >= 8.0.0, < 8.0.31, >= 9.0.0.M0, < 9.0.0.M2 7.0.68, 8.0.31, 9.0.0.M2
  21. Apache Tomcat does not enforce the maxHttpHeaderSize limit
    High · 7.5 CVE-2011-0534 >= 6.0.0, < 6.0.32, >= 7.0.0, < 7.0.8 6.0.32, 7.0.8
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