What’s Vulnerable › Vulnerabilities

CVE-2025-53506: Apache Tomcat: DoS via excessive h2 streams at connection start

• Severity: high (CVSS 7.5 v3.1)
• Exploited in the wild: not listed in CISA KEV
• EPSS: 2.1% probability of exploitation in the next 30 days
• Public exploit or detection template: none known
• Published: 2025-07-10 · updated 2026-06-17
• Weakness: CWE-400

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-M1 through 11.0.8, from 10.1.0-M1 through 10.1.42, from 9.0.0.M1 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.

Affected products

• Apache Tomcat: from 9.0.0 through 9.0.106; from 10.1.0 through 10.1.42; from 11.0.0 through 11.0.8

References

• https://lists.apache.org/thread/p09775q0rd185m6zz98krg0fp45j8kr0
• http://www.openwall.com/lists/oss-security/2025/07/10/13
• https://lists.debian.org/debian-lts-announce/2025/07/msg00009.html

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