CVE-2024-40898·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 0.47% — higher than 64% 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-2024-40898 scores 7.5 on CVSS, so a successful attack would be serious — but at 0.47%, 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 2.4.62 or later to address this server-side request forgery vulnerability affecting Windows deployments with mod_rewrite. Organizations running Apache on Windows should prioritize this update to prevent potential credential leakage through malicious rewrite rules that could redirect internal requests to attacker-controlled servers.

sudo dnf update httpd

What an exploitation attempt looks like

Sample log line indicative of exploitation attempts:

POST|GET|HEAD requests containing unusual 'Host:' headers pointing to internal IP ranges (127.0.0.1, 10.0.0.0/8, 172.16.0.0/12, 192.168.0.0/16) combined with mod_rewrite rule triggers; alternatively, log entries showing 'mod_rewrite' rules redirecting to external URLs with NTLM authentication headers

WAF mitigation (if patching is not yet possible)

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

Implement WAF rules to block requests with rewrite-triggering patterns that attempt to redirect traffic to private IP ranges or external hosts not in an allowlist. Restrict mod_rewrite directives in .htaccess files and enforce strict input validation on parameters that feed into rewrite rules.

How to check if you are affected

1. Step 1: Check Apache version with 'apache2 -v' (Debian/Ubuntu) or 'httpd -v' (RHEL/CentOS) and confirm it is below 2.4.62
2. Step 2: Verify mod_rewrite is enabled by running 'apache2ctl -M | grep rewrite' or 'httpctl -M | grep rewrite' and check for rewrite rules in server or vhost context
3. Step 3: Search Apache access and error logs for suspicious external requests or failed connection attempts: 'grep -E "CONNECT|tunnel|proxy" /var/log/apache2/error.log'
4. Step 4: After patching, run 'apache2ctl -v' or 'httpctl -v' to confirm version is 2.4.62 or higher, then restart the service with 'sudo systemctl restart apache2' or 'sudo systemctl restart httpd'

FAQ

Related Apache CVEs

References

• https://httpd.apache.org/security/vulnerabilities_24.html
• http://www.openwall.com/lists/oss-security/2024/07/17/7
• https://httpd.apache.org/security/vulnerabilities_24.html
• https://security.netapp.com/advisory/ntap-20240808-0006/