CVE-2024-38476·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 3.5% — higher than 87% 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.

Affected versions

How to fix this CVE

Upgrade Apache HTTP Server to version 2.4.60 or later immediately to patch a critical vulnerability that allows attackers to exploit malicious backend response headers for information disclosure, server-side request forgery, or code execution. Organizations running Apache 2.4.59 or earlier should prioritize this update as a critical security patch. After upgrading, validate the installation and restart the Apache service to ensure the fix is active.

sudo dnf update httpd httpd-core httpd-tools -y

What an exploitation attempt looks like

Sample log line indicative of exploitation attempts:

POST|GET .* HTTP/1.1.*\r\nX-.*:|Set-Cookie:.*exploit|Location:.*\$|Content-Disposition:.*exec|Transfer-Encoding:.*chunked.*\r\n0\r\n\r\n.*script

WAF mitigation (if patching is not yet possible)

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

Implement strict header validation rules that reject or sanitize response headers containing executable code patterns, script tags, or SSRF-indicative values. Block requests with malformed or oversized response headers. If using mod_proxy, apply rules to validate backend response headers before they are processed by the main Apache engine. Use ModSecurity with ruleset CRS to detect header injection attempts.

How to check if you are affected

1. Run 'apache2 -v' or 'httpd -v' to check the installed Apache version; vulnerable if version is 2.4.0 through 2.4.59
2. Check which Apache modules are enabled using 'apache2ctl -M' or 'httpctl -M' to understand potential attack vectors through proxy or backend integration
3. Search Apache error and access logs for unusual response header patterns: grep -r 'malformed\|invalid\|exploit' /var/log/apache2/ or equivalent log directory
4. After patching, verify the new version with 'apache2 -v' and confirm service restart was successful using 'systemctl status apache2' or 'service apache2 status'

FAQ

Related Apache CVEs

References

• https://httpd.apache.org/security/vulnerabilities_24.html
• https://security.netapp.com/advisory/ntap-20240712-0001/
• http://seclists.org/fulldisclosure/2024/Oct/11
• http://www.openwall.com/lists/oss-security/2024/07/01/9
• https://httpd.apache.org/security/vulnerabilities_24.html