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How the CVE Works
CVE-2025-49630 exploits a vulnerability in Apache HTTP Server (versions 2.4.26 to 2.4.63) when configured as a reverse proxy with HTTP/2 backend and `ProxyPreserveHost` enabled. An attacker sends maliciously crafted requests to the proxy, triggering an assertion failure in mod_proxy_http2, causing the server to crash. This results in a denial of service, disrupting legitimate traffic. The flaw arises from improper handling of host headers during HTTP/2 request processing, leading to an unstable state.
DailyCVE Form
Platform: Apache HTTP Server
Version: 2.4.26 – 2.4.63
Vulnerability: DoS via assertion
Severity: Critical
Date: 07/29/2025
Prediction: Patch by 08/15/2025
What Undercode Say
Check Apache version httpd -v Test proxy config curl -I http://target/proxy-endpoint Debug mod_proxy_http2 tail -f /var/log/apache2/error.log
How Exploit
1. Craft HTTP/2 request with malformed host header.
2. Send to reverse proxy with `ProxyPreserveHost on`.
3. Trigger assertion crash in `mod_proxy_http2`.
Protection from this CVE
- Disable
ProxyPreserveHost. - Upgrade to patched version.
- Restrict client IPs.
Impact
- Service disruption.
- Downtime for reverse-proxied apps.
- High availability risk.
Sources:
Reported By: nvd.nist.gov
Extra Source Hub:
Undercode
