CVE-2025-49630: Apache HTTP Server: mod_proxy_http2 denial of service

Severity: high (CVSS 7.5 v3.1)
Exploited in the wild: not listed in CISA KEV
EPSS: 1.4% 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-617

Description

In certain proxy configurations, a denial of service attack against Apache HTTP Server versions 2.4.26 through to 2.4.63 can be triggered by untrusted clients causing an assertion in mod_proxy_http2. Configurations affected are a reverse proxy is configured for an HTTP/2 backend, with ProxyPreserveHost set to "on".

Affected products

Apache HTTP Server: from 2.4.26 before 2.4.64 — fixed in 2.4.64

How to fix

Upgrade to a fixed version: Apache HTTP Server 2.4.64. Check the vendor advisory for mitigations.

References

https://httpd.apache.org/security/vulnerabilities_24.html
http://www.openwall.com/lists/oss-security/2025/07/10/2
http://www.openwall.com/lists/oss-security/2025/07/10/7
https://lists.debian.org/debian-lts-announce/2025/08/msg00009.html

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