CVE-2026-56449·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 0.61% — higher than 48% 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-2026-56449 scores 7.5 on CVSS, so a successful attack would be serious — but at 0.61%, 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 2.4.69 or later to patch the out-of-bounds write vulnerability in mod_proxy_html that can be triggered by malicious HTTP response bodies. Organizations should prioritize this update as the vulnerability affects all versions from 2.4.0 through 2.4.68 and can lead to memory corruption when the proxy_html module processes untrusted responses from upstream servers.

sudo dnf update httpd

What an exploitation attempt looks like

Sample log line indicative of exploitation attempts:

POST/GET requests to proxied endpoints followed by HTTP 5xx errors or segmentation fault entries in error logs; look for malformed Content-Type headers or extremely large Content-Length values in upstream responses that trigger buffer overflows in HTML rewriting logic

WAF mitigation (if patching is not yet possible)

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

Implement a WAF rule to validate and sanitize HTTP response Content-Length headers from upstream servers; limit the maximum size of HTML response bodies processed by mod_proxy_html to prevent triggering out-of-bounds writes

How to check if you are affected

1. Step 1: Check Apache version with `apachectl -v` or `apache2ctl -v` and verify it is 2.4.69 or later
2. Step 2: Confirm mod_proxy_html is loaded by running `apache2ctl -M | grep proxy_html` (Ubuntu/Debian) or `httpd -M | grep proxy_html` (RHEL/CentOS)
3. Step 3: Search Apache error logs for segmentation faults or memory-related errors: `grep -i 'segfault\|out of bounds\|memory' /var/log/apache2/error.log` or equivalent path
4. Step 4: After patching, restart Apache with `sudo systemctl restart apache2` (Ubuntu/Debian) or `sudo systemctl restart httpd` (RHEL/CentOS) and verify no errors in logs

FAQ

Related Apache CVEs

References

• https://httpd.apache.org/security/vulnerabilities_24.html
• http://www.openwall.com/lists/oss-security/2026/10/01/18