CVE-2021-40438 — Security Box Score

CVE · referencelatest edition

Reference page — cumulative record through Wednesday, August 19, 2026 UTC. Reference pages update as the archive grows; only dated daily editions are immutable pages of record.

CVE-2021-40438CRITICAL

Apache Software Foundation Apache HTTP Server — mod_proxy SSRF

  AV  AC  PR  UI  S  C  I  A   CVSS     EPSS    %ile   KEV
   N   H   N   N  C  H  H  H    9.0   1.0000   100.0   YES

AFFECTED
  Product             Versions                  Fixed
  Apache HTTP Server  Apache HTTP Server 2.4 –  —

TIMELINE
  Sep 2   Reserved by apache
  Dec 1   Added to CISA KEV, remediation due 2021-12-15
  Dec 1   Published (CNA: apache)

CWE-918 · CNA: apache · CVSS v3.1 · 20 references · NVD status: Analyzed · KEV due December 15, 2021

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.

Lifecycle

Complete event history — 3 events, chronological
Date	Event	Detail
September 2, 2021	Reserved	Reserved by apache
December 1, 2021	KEV ADDED	Added to CISA KEV, remediation due 2021-12-15
December 1, 2021	Published	Published (CNA: apache)

Affected

Affected products and packages — 1 row
Vendor	Product / Package	Ecosystem	Version introduced	Fixed
Apache Software Foundation	Apache HTTP Server	—	Apache HTTP Server 2.4	—

Weaknesses

CWE-918

References (20)

https://cert-portal.siemens.com/productcert/pdf/ssa-685781.pdf [Third Party Advisory]
https://httpd.apache.org/security/vulnerabilities_24.html [Release Notes, Vendor Advisory]
https://lists.apache.org/thread.html/r210807d0bb55f4aa6fbe1512be6bcc4dacd64e84940429fba329967a%40%3Cusers.httpd.apache.org%3E [Mailing List]
https://lists.apache.org/thread.html/r2eb200ac1340f69aa22af61ab34780c531d110437910cb9c0ece3b37%40%3Cbugs.httpd.apache.org%3E [Mailing List]
https://lists.apache.org/thread.html/r3925e167d5eb1c75def3750c155d753064e1d34a143028bb32910432%40%3Cusers.httpd.apache.org%3E [Mailing List]
https://lists.apache.org/thread.html/r61fdbfc26ab170f4e6492ef3bd5197c20b862ce156e9d5a54d4b899c%40%3Cusers.httpd.apache.org%3E [Mailing List]
https://lists.apache.org/thread.html/r82838efc5fa6fc4c73986399c9b71573589f78b31846aff5bd9b1697%40%3Cusers.httpd.apache.org%3E [Mailing List]
https://lists.apache.org/thread.html/r82c077663f9759c7df5a6656f925b3ee4f55fcd33c889ba7cd687029%40%3Cusers.httpd.apache.org%3E [Mailing List]
https://lists.apache.org/thread.html/rf6954e60b1c8e480678ce3d02f61b8a788997785652e9557a3265c00%40%3Cusers.httpd.apache.org%3E [Mailing List]
https://lists.debian.org/debian-lts-announce/2021/10/msg00001.html [Mailing List, Third Party Advisory]
https://lists.fedoraproject.org/archives/list/package-announce%40lists.fedoraproject.org/message/SPBR6WUYBJNACHKE65SPL7TJOHX7RHWD/ [Release Notes]
https://lists.fedoraproject.org/archives/list/package-announce%40lists.fedoraproject.org/message/ZNCYSR3BXT36FFF4XTCPL3HDQK4VP45R/ [Release Notes]
https://security.gentoo.org/glsa/202208-20 [Third Party Advisory]
https://security.netapp.com/advisory/ntap-20211008-0004/ [Third Party Advisory]
https://tools.cisco.com/security/center/content/CiscoSecurityAdvisory/cisco-sa-apache-httpd-2.4.49-VWL69sWQ [Broken Link, Third Party Advisory]
https://www.cisa.gov/known-exploited-vulnerabilities-catalog?field_cve=CVE-2021-40438 [US Government Resource]
https://www.debian.org/security/2021/dsa-4982 [Mailing List, Third Party Advisory]
https://www.oracle.com/security-alerts/cpuapr2022.html [Patch, Third Party Advisory]
https://www.oracle.com/security-alerts/cpujan2022.html [Patch, Third Party Advisory]
https://www.tenable.com/security/tns-2021-17 [Third Party Advisory]

Authoritative record: CVE-2021-40438 at cve.org

Vendors: apache

Weaknesses: CWE-918

About this page

This is a reference page, not a dated page of record. It assembles the complete lifecycle of CVE-2021-40438 from the CVE Program record, NVD enrichment, the CISA KEV catalog, EPSS, and OSV advisories. The box score's numbers (CVSS, EPSS, KEV status) are current as of Wednesday, August 19, 2026 UTC and are re-derived as the archive grows; only dated daily editions are immutable pages of record. The authoritative source for this identifier is cve.org.