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High

Apache Tomcat Denial of Service vulnerability

  • Disclosed: 15.06.2020
  • Updated: 11.10.2026 12:22

The HTTP/2 implementation in Apache Tomcat 9.0.0.M1 to 9.0.14 and 8.5.0 to 8.5.37 accepted streams with excessive numbers of SETTINGS frames and also permitted clients to keep streams open without reading/writing request/response data. By keeping streams open for requests that utilised the Servlet API's blocking I/O, clients were able to cause server-side threads to block eventually leading to thread exhaustion and a DoS.

Affected software

Click a technology to see all vulnerabilities affecting it.

PlatformPackageVulnerable versionsFixed in
Java / Kotlin (Maven) org.apache.tomcat.embed:tomcat-embed-core >= 9.0.0, < 9.0.16, >= 8.0.0, < 8.5.38 9.0.16, 8.5.38
Java / Kotlin (Maven) org.apache.tomcat:tomcat-coyote >= 9.0.0, < 9.0.16, >= 8.0.0, < 8.5.38 9.0.16, 8.5.38

References

CVSS score 7.5/10
CVSS vector
CVSS:3.0/AV:N/AC:L/PR:N/UI:N/S:U/C:N/I:N/A:H
Weakness (CWE)
CWE-400
Platform
Java / Kotlin (Maven)
Package
org.apache.tomcat.embed:tomcat-embed-core, org.apache.tomcat:tomcat-coyote
Disclosed
15.06.2020
Updated
11.10.2026 12:22

Sources and licenses

OSV / GitHub Advisory Database - GHSA-qcxh-w3j9-58qr - CC BY 4.0

Vulnerability history: org.apache.tomcat.embed:tomcat-embed-core

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 (77) in the archive
Total entries
77
First → latest
10.2018 08.2026
Without a fix
0
Exploited in attacks
5

Severity breakdown

  • Critical 11
  • High 36
  • Medium 25
  • Low 5

Disclosures per year

Severity:
  1. Apache Tomcat Denial of Service vulnerability this entry
    High · 7.5 CVE-2019-0199 >= 9.0.0, < 9.0.16, >= 8.0.0, < 8.5.38 9.0.16, 8.5.38
  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 has an HTTP Request/Response Smuggling vulnerability
    High · 7.5 CVE-2026-24880 >= 7.0.0, < 9.0.116, >= 10.1.0-M1, < 10.1.52, >= 11.0.0-M1, < 11.0.20 9.0.116, 10.1.52, 11.0.20
  14. 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
  15. Apache Tomcat has an Improper Input Validation vulnerability
    High · 7.5 CVE-2026-24734 >= 11.0.0-M1, < 11.0.18, >= 10.1.0-M7, < 10.1.52, >= 9.0.83, < 9.0.115 11.0.18, 10.1.52, 9.0.115
  16. 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
  17. Apache Tomcat Improper Resource Shutdown or Release vulnerability
    High · 7.5 CVE-2025-48989 >= 11.0.0-M1, < 11.0.10, >= 10.1.0-M1, < 10.1.44, >= 9.0.0.M1, < 9.0.108 11.0.10, 10.1.44, 9.0.108
  18. Apache Tomcat Coyote vulnerable to Denial of Service via excessive HTTP/2 streams
    High · 7.5 CVE-2025-53506 >= 8.5.0, <= 8.5.100, >= 9.0.0.M1, < 9.0.107, >= 10.1.0-M1, < 10.1.43, >= 11.0.0-M1, < 11.0.9 9.0.107, 10.1.43, 11.0.9
  19. Apache Tomcat Catalina is vulnerable to DoS attack through bypassing of size limits
    High · 7.5 CVE-2025-52520 >= 11.0.0-M1, < 11.0.9, >= 10.1.0-M1, < 10.1.43, >= 9.0.0.M1, < 9.0.107, >= 8.5.0, <= 8.5.100 11.0.9, 10.1.43, 9.0.107
  20. Apache Tomcat - DoS in multipart upload
    High · 7.5 CVE-2025-48988 >= 11.0.0-M1, < 11.0.8, >= 10.1.0-M1, < 10.1.42, >= 9.0.0.M1, < 9.0.106, >= 8.5.0, <= 8.5.100 11.0.8, 10.1.42, 9.0.106
  21. Apache Tomcat: Potential RCE and/or information disclosure and/or information corruption with partial PUT
    Critical · 9.8 Exploited in attacks CVE-2025-24813 >= 11.0.0-M1, < 11.0.3, >= 10.1.0-M1, < 10.1.35, >= 9.0.0.M1, < 9.0.99, >= 8.5.0, <= 8.5.100 11.0.3, 10.1.35, 9.0.99
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