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Posted to announce@apache.org by Mark Thomas <ma...@apache.org> on 2026/09/23 10:01:55 UTC

[SECURITY] CVE-2026-78437 Apache Tomcat - HTTP/2 DoS via malformed request

CVE-2026-78437 Apache Tomcat - HTTP/2 DoS via malformed request

Severity: Low

Vendor: The Apache Software Foundation

Versions Affected:
Apache Tomcat 11.0.19 to 11.0.25
Apache Tomcat 10.1.53 to 10.1.59
Apache Tomcat 9.0.116 to 9.0.121

Description:
A malformed HTTP/2 request could potentially (depends on timing) cause 
one request from another user to fail.

Mitigation:
Users of the affected versions should apply one of the following
mitigations:
- Remove the examples web application
- Upgrade to Apache Tomcat 11.0.26
- Upgrade to Apache Tomcat 10.1.60
- Upgrade to Apache Tomcat 9.0.122

History:
2026-09-23 Original advisory

References:
[1] https://tomcat.apache.org/security-11.html
[2] https://tomcat.apache.org/security-10.html
[3] https://tomcat.apache.org/security-9.html














[UPDATE][SECURITY] CVE-2026-78437 Apache Tomcat - HTTP/2 DoS via malformed request

Posted by Mark Thomas <ma...@apache.org>.
CVE-2026-78437 Apache Tomcat - HTTP/2 DoS via malformed request

Severity: Low

Vendor: The Apache Software Foundation

Versions Affected:
Apache Tomcat 11.0.19 to 11.0.25
Apache Tomcat 10.1.53 to 10.1.59
Apache Tomcat 9.0.116 to 9.0.121

Description:
A malformed HTTP/2 request could potentially (depends on timing) cause 
one request from another user to fail.

Mitigation:
Users of the affected versions should apply one of the following
mitigations:
- Upgrade to Apache Tomcat 11.0.26
- Upgrade to Apache Tomcat 10.1.60
- Upgrade to Apache Tomcat 9.0.122

History:
2026-09-28 Correction. Removing the examples app is not a mitigation
2026-09-23 Original advisory

References:
[1] https://tomcat.apache.org/security-11.html
[2] https://tomcat.apache.org/security-10.html
[3] https://tomcat.apache.org/security-9.html














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[UPDATE][SECURITY] CVE-2026-78437 Apache Tomcat - HTTP/2 DoS via malformed request

Posted by Mark Thomas <ma...@apache.org>.
CVE-2026-78437 Apache Tomcat - HTTP/2 DoS via malformed request

Severity: Low

Vendor: The Apache Software Foundation

Versions Affected:
Apache Tomcat 11.0.19 to 11.0.25
Apache Tomcat 10.1.53 to 10.1.59
Apache Tomcat 9.0.116 to 9.0.121

Description:
A malformed HTTP/2 request could potentially (depends on timing) cause 
one request from another user to fail.

Mitigation:
Users of the affected versions should apply one of the following
mitigations:
- Upgrade to Apache Tomcat 11.0.26
- Upgrade to Apache Tomcat 10.1.60
- Upgrade to Apache Tomcat 9.0.122

History:
2026-09-28 Correction. Removing the examples app is not a mitigation
2026-09-23 Original advisory

References:
[1] https://tomcat.apache.org/security-11.html
[2] https://tomcat.apache.org/security-10.html
[3] https://tomcat.apache.org/security-9.html














[UPDATE][SECURITY] CVE-2026-78437 Apache Tomcat - HTTP/2 DoS via malformed request

Posted by Mark Thomas <ma...@apache.org>.
CVE-2026-78437 Apache Tomcat - HTTP/2 DoS via malformed request

Severity: Low

Vendor: The Apache Software Foundation

Versions Affected:
Apache Tomcat 11.0.19 to 11.0.25
Apache Tomcat 10.1.53 to 10.1.59
Apache Tomcat 9.0.116 to 9.0.121

Description:
A malformed HTTP/2 request could potentially (depends on timing) cause 
one request from another user to fail.

Mitigation:
Users of the affected versions should apply one of the following
mitigations:
- Upgrade to Apache Tomcat 11.0.26
- Upgrade to Apache Tomcat 10.1.60
- Upgrade to Apache Tomcat 9.0.122

History:
2026-09-28 Correction. Removing the examples app is not a mitigation
2026-09-23 Original advisory

References:
[1] https://tomcat.apache.org/security-11.html
[2] https://tomcat.apache.org/security-10.html
[3] https://tomcat.apache.org/security-9.html














[UPDATE][SECURITY] CVE-2026-78437 Apache Tomcat - HTTP/2 DoS via malformed request

Posted by Mark Thomas <ma...@apache.org>.
CVE-2026-78437 Apache Tomcat - HTTP/2 DoS via malformed request

Severity: Low

Vendor: The Apache Software Foundation

Versions Affected:
Apache Tomcat 11.0.19 to 11.0.25
Apache Tomcat 10.1.53 to 10.1.59
Apache Tomcat 9.0.116 to 9.0.121

Description:
A malformed HTTP/2 request could potentially (depends on timing) cause 
one request from another user to fail.

Mitigation:
Users of the affected versions should apply one of the following
mitigations:
- Upgrade to Apache Tomcat 11.0.26
- Upgrade to Apache Tomcat 10.1.60
- Upgrade to Apache Tomcat 9.0.122

History:
2026-09-28 Correction. Removing the examples app is not a mitigation
2026-09-23 Original advisory

References:
[1] https://tomcat.apache.org/security-11.html
[2] https://tomcat.apache.org/security-10.html
[3] https://tomcat.apache.org/security-9.html














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[UPDATE][SECURITY] CVE-2026-78437 Apache Tomcat - HTTP/2 DoS via malformed request

Posted by Mark Thomas via users <us...@tomcat.apache.org>.
CVE-2026-78437 Apache Tomcat - HTTP/2 DoS via malformed request

Severity: Low

Vendor: The Apache Software Foundation

Versions Affected:
Apache Tomcat 11.0.19 to 11.0.25
Apache Tomcat 10.1.53 to 10.1.59
Apache Tomcat 9.0.116 to 9.0.121

Description:
A malformed HTTP/2 request could potentially (depends on timing) cause 
one request from another user to fail.

Mitigation:
Users of the affected versions should apply one of the following
mitigations:
- Upgrade to Apache Tomcat 11.0.26
- Upgrade to Apache Tomcat 10.1.60
- Upgrade to Apache Tomcat 9.0.122

History:
2026-09-28 Correction. Removing the examples app is not a mitigation
2026-09-23 Original advisory

References:
[1] https://tomcat.apache.org/security-11.html
[2] https://tomcat.apache.org/security-10.html
[3] https://tomcat.apache.org/security-9.html

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[UPDATE][SECURITY] CVE-2026-78437 Apache Tomcat - HTTP/2 DoS via malformed request

Posted by Mark Thomas via dev <de...@tomcat.apache.org>.
CVE-2026-78437 Apache Tomcat - HTTP/2 DoS via malformed request

Severity: Low

Vendor: The Apache Software Foundation

Versions Affected:
Apache Tomcat 11.0.19 to 11.0.25
Apache Tomcat 10.1.53 to 10.1.59
Apache Tomcat 9.0.116 to 9.0.121

Description:
A malformed HTTP/2 request could potentially (depends on timing) cause 
one request from another user to fail.

Mitigation:
Users of the affected versions should apply one of the following
mitigations:
- Upgrade to Apache Tomcat 11.0.26
- Upgrade to Apache Tomcat 10.1.60
- Upgrade to Apache Tomcat 9.0.122

History:
2026-09-28 Correction. Removing the examples app is not a mitigation
2026-09-23 Original advisory

References:
[1] https://tomcat.apache.org/security-11.html
[2] https://tomcat.apache.org/security-10.html
[3] https://tomcat.apache.org/security-9.html

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