CVE-2025-53506
Apache Tomcat: DoS via excessive h2 streams at connection start
Description
Uncontrolled Resource Consumption vulnerability in Apache Tomcat if an HTTP/2 client did not acknowledge the initial settings frame that reduces the maximum permitted concurrent streams. This issue affects Apache Tomcat: from 11.0.0 through 11.0.8, from 10.1.0 through 10.1.42, from 9.0.0 through 9.0.106. The following versions were EOL at the time the CVE was created but are known to be affected: 8.5.0 through 8.5.100. Other EOL versions may also be affected. Users are recommended to upgrade to version 11.0.9, 10.1.43 or 9.0.107, which fix the issue.
How to fix CVE-2025-53506
To remediate CVE-2025-53506, upgrade the affected package to a fixed version below.
- —upgrade to 9.0.107 or later
- —upgrade to 10.1.52-1~deb12u1 or later
- —upgrade to 11.0.15-1~deb13u1 or later
- —upgrade to 9.0.107-0+deb11u1 or later
- —no fix listed
- —upgrade to 11.0.9 or later
Is CVE-2025-53506 being exploited?
Low — EPSS is 1.9%, meaning exploitation activity has not been observed at scale.
Affected packages (6)
- from 0, < 9.0.107, >= 10.0.0, < 10.1.43, >= 11.0.0, < 11.0.9
- from 0, < 10.1.52-1~deb12u1
- from 0, < 11.0.15-1~deb13u1
- from 0, < 9.0.107-0+deb11u1
- >= 8.5.0, <= 8.5.100
- >= 11.0.0-M1, < 11.0.9
CVSS scores
| Source | Version | Severity | Vector |
|---|---|---|---|
| osv | CVSS 3.1 | HIGH7.5 | CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:N/I:N/A:H |