CVE-2025-49630·Apache vulnerability

How likely is exploitation

FIRST's Exploit Prediction Scoring System puts the probability of this CVE being exploited in the next 30 days at 0.79% — higher than 74% of all published CVEs. EPSS is an independent forecast of exploitation, not a severity rating: it says nothing about how much damage a successful attack does, which is what a CVSS score measures.

Read the two together. CVE-2025-49630 scores 7.5 on CVSS, so a successful attack would be serious — but at 0.79%, almost nobody is currently attempting it. That is a different situation from a flaw under mass exploitation, and it is usually the difference between patching on your next maintenance window and patching tonight.

Affected versions

How to fix this CVE

Upgrade Apache HTTP Server to version 2.4.64 or later to patch the assertion failure in mod_proxy_http2. This vulnerability specifically affects reverse proxy configurations with HTTP/2 backends and ProxyPreserveHost enabled, making it critical to update if your deployment matches this setup. Apply the update during a maintenance window and restart the Apache service to ensure the fix is active.

sudo dnf update httpd && sudo systemctl restart httpd

What an exploitation attempt looks like

Sample log line indicative of exploitation attempts:

GET|POST|HEAD|OPTIONS|CONNECT|TRACE|DELETE|PUT|PATCH requests originating from untrusted networks to a reverse proxy endpoint followed by Apache error log entries containing 'mod_proxy_http2', 'Assertion', or 'core:notice', with corresponding process termination (exit code 134 or 139)

WAF mitigation (if patching is not yet possible)

Add this rule to your WAF to block exploitation attempts while you schedule the patch.

Configure rate limiting and connection limits on reverse proxy endpoints to reduce the impact of DoS attempts. Block or throttle requests from sources sending malformed HTTP/2 frames. Implement request timeout policies to prevent slowdown attacks. However, WAF rules cannot fully prevent this assertion-level vulnerability; upgrading Apache is mandatory.

How to check if you are affected

1. Run 'apache2ctl -v' or 'httpd -v' to check the installed Apache version; versions 2.4.26 through 2.4.63 are vulnerable
2. Check your Apache configuration file (typically /etc/apache2/sites-enabled/*.conf or /etc/httpd/conf.d/*.conf) for ProxyPreserveHost On combined with ProxyPass directives pointing to HTTP/2 backends
3. Search Apache error logs (/var/log/apache2/error.log or /var/log/httpd/error_log) for assertion failures or segmentation faults from mod_proxy_http2 with patterns like 'Assertion.*failed' or 'SIGABRT'
4. Verify the patch was applied by re-running 'apache2ctl -v' or 'httpd -v' and confirming the version is 2.4.64 or later, then check 'systemctl status apache2' or 'systemctl status httpd' shows the service is running

FAQ

Related Apache CVEs

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