CVE-2021-40438
Apache Software Foundation Apache HTTP Server
Summary
A crafted request uri-path can cause mod_proxy to forward the request to an origin server choosen by the remote user. This issue affects Apache HTTP Server 2.4.48 and earlier.
Published: 2021-09-16
Analysis
🟠 High — imminent exploitation
Weakness: Server-Side Request Forgery (SSRF) (CWE-918). Forces the server to make requests to internal targets.
How it's exploited: Exploitable over the network (internet-reachable), unauthenticated, no user interaction, with high complexity. The flaw can pivot to other components (scope changed).
Impact: Full compromise (confidentiality, integrity and availability).
Status: Exploit probability (EPSS, 30 days): 100% — high.
- Apply the vendor patch according to risk priority.
- Reduce exposure: keep it off the internet; firewall, VPN or network segmentation.
- Detect: turn this CVE into detection rules.
MITRE ATT&CK technique: T1190 · Exploit Public-Facing Application
Practice it in the arsenal: WAF Bypass
CVSS vector
CVSS:3.1/AV:N/AC:H/PR:N/UI:N/S:C/C:H/I:H/A:H
The vector encodes how it's exploited (translated above, in the analysis). Break it down in the CVSS tool →
Sources: CISA KEV · EPSS · FIRST.org · NVD. Analysis derived from the CVSS vector and exploitation status (no AI). Informational; always verify against the vendor's official advisory.