CVE-2021-40438Actively exploitedAdded to KEV 2021-12-01Known ransomware campaign use

Apache HTTP Server-Side Request Forgery (SSRF)

Apache, Apache

Description

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.

CVSS severity for this advisory hasn't been enriched from NVD yet, check back shortly.

EPSS, exploit probability

Critical

100.0%

estimated chance of real-world exploitation in the next 30 days, higher than 100.0% of every CVE FIRST.org scores

Refreshed 10/28/2026, via FIRST.org's EPSS model, not CVSS, this measures likelihood of exploitation, not how severe it would be.

Required action

Apply updates per vendor instructions.

CISA-recommended due date: 2021-12-15

CWE-918

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