Apache HTTP Server-Side Request Forgery (SSRF)

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.

CheckOps priority index

9.6/10 Patch within 24 h

Severity9.0

Probability10.0

Exploitation5/5

Severity = CVSS. Probability = EPSS (FIRST). Exploitation = public signals: KEV, EUVD, ransomware, EPSS above 10 %, no account required.

EPSS · today 100.00% higher than 100.00% of CVEs

CVSS 3.1 9.0 AV:N/AC:H/PR:N/UI:N/S:C/C:H/I:

Exploited for 1,798 days 01 Dec 2021

CISA due date 15 Dec 2021 for US federal agencies

Exploitation probability EPSS · FIRST

EPSS probability (%)Percentile among all CVEs

Exploitation signals 5 / 5

KEV catalog (CISA)01 Dec 2021
Exploited in EUVD (ENISA)01 Dec 2021
Used by ransomwareyes
EPSS above 10 %100.00%
No account, over the networkyes

What to do

Fix

Update to a fixed version: 2.4.49-1

CISA guidance: Apply updates per vendor instructions.

Meanwhile

Take the service off the internet or restrict access to it, watch the logs and look for signs of compromise.

Manufacturers (CRA)

Exploited vulnerability in your product: early warning to ENISA within 24 h, then notification within 72 h (Article 14 of the Cyber Resilience Act). The CRA explained

Affected products

Apache HTTP ServerApache

Affected versions

Apache HTTP Server 2.4 ≤2.4.48

Weaknesses (CWE)

CWE-918

Open source packages OSV

apache2Debian:13 · CVE-2021-40438
fixed in 2.4.49-1

Timeline

16 Sept 2021
Published
01 Dec 2021
Exploitation reported (ENISA)
01 Dec 2021
Added to the KEV catalog
15 Dec 2021
CISA remediation due date
26 Sept 2026
EPSS peak: 100.00%

Other exploited vulnerabilities from the same vendor

CVE-2016-3081Apache Struts Command Injection Vulnerability
8.5 · Rising fast
CVE-2026-34486Apache Tomcat Missing Encryption of Sensitive Data Vulnerability
8.4 · Actively exploited
CVE-2026-34197Apache ActiveMQ Improper Input Validation Vulnerability
8.3 · Background exploitation
CVE-2024-38475Apache HTTP Server Improper Escaping of Output Vulnerability
9.0 · Background exploitation
CVE-2025-24813Apache Tomcat Path Equivalence Vulnerability
9.4 · Background exploitation
CVE-2024-45195Apache OFBiz Forced Browsing Vulnerability
9.3 · Background exploitation