CVE-2021-40438

9.0 CRITICAL CISA KEV - Actively Exploited
Published: September 16, 2021 Modified: October 27, 2025
View on NVD

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.

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CVSS v3.x Details

0.0 Low Medium High Critical 10.0
Vector String
CVSS:3.1/AV:N/AC:H/PR:N/UI:N/S:C/C:H/I:H/A:H

References to Advisories, Solutions, and Tools

Patch Vendor Advisory Exploit Third Party Advisory
https://cert-portal.siemens.com/productcert/pdf/ssa-685781.pdf
Source: security@apache.org
Third Party Advisory
https://httpd.apache.org/security/vulnerabilities_24.html
Source: security@apache.org
Release Notes Vendor Advisory
https://lists.apache.org/thread.html/r210807d0bb55f4aa6fbe1512be6bcc4dacd64e84940429fba329967a%40%3Cusers.httpd.apache.org%3E
Source: security@apache.org
Mailing List
https://lists.apache.org/thread.html/r2eb200ac1340f69aa22af61ab34780c531d110437910cb9c0ece3b37%40%3Cbugs.httpd.apache.org%3E
Source: security@apache.org
Mailing List
https://lists.apache.org/thread.html/r3925e167d5eb1c75def3750c155d753064e1d34a143028bb32910432%40%3Cusers.httpd.apache.org%3E
Source: security@apache.org
Mailing List
https://lists.apache.org/thread.html/r61fdbfc26ab170f4e6492ef3bd5197c20b862ce156e9d5a54d4b899c%40%3Cusers.httpd.apache.org%3E
Source: security@apache.org
Mailing List
https://lists.apache.org/thread.html/r82838efc5fa6fc4c73986399c9b71573589f78b31846aff5bd9b1697%40%3Cusers.httpd.apache.org%3E
Source: security@apache.org
Mailing List
https://lists.apache.org/thread.html/r82c077663f9759c7df5a6656f925b3ee4f55fcd33c889ba7cd687029%40%3Cusers.httpd.apache.org%3E
Source: security@apache.org
Mailing List
https://lists.apache.org/thread.html/rf6954e60b1c8e480678ce3d02f61b8a788997785652e9557a3265c00%40%3Cusers.httpd.apache.org%3E
Source: security@apache.org
Mailing List
https://lists.debian.org/debian-lts-announce/2021/10/msg00001.html
Source: security@apache.org
Mailing List Third Party Advisory
https://lists.fedoraproject.org/archives/list/package-announce%40lists.fedoraproject.org/message/SPBR6WUYBJNACHKE65SPL7TJOHX7RHWD/
Source: security@apache.org
Release Notes
https://lists.fedoraproject.org/archives/list/package-announce%40lists.fedoraproject.org/message/ZNCYSR3BXT36FFF4XTCPL3HDQK4VP45R/
Source: security@apache.org
Release Notes
https://security.gentoo.org/glsa/202208-20
Source: security@apache.org
Third Party Advisory
https://security.netapp.com/advisory/ntap-20211008-0004/
Source: security@apache.org
Third Party Advisory
https://tools.cisco.com/security/center/content/CiscoSecurityAdvisory/cisco-sa-apache-httpd-2.4.49-VWL69sWQ
Source: security@apache.org
Broken Link Third Party Advisory
https://www.debian.org/security/2021/dsa-4982
Source: security@apache.org
Mailing List Third Party Advisory
https://www.oracle.com/security-alerts/cpuapr2022.html
Source: security@apache.org
Patch Third Party Advisory
https://www.oracle.com/security-alerts/cpujan2022.html
Source: security@apache.org
Patch Third Party Advisory
https://www.tenable.com/security/tns-2021-17
Source: security@apache.org
Third Party Advisory
https://cert-portal.siemens.com/productcert/pdf/ssa-685781.pdf
Source: af854a3a-2127-422b-91ae-364da2661108
Third Party Advisory
https://httpd.apache.org/security/vulnerabilities_24.html
Source: af854a3a-2127-422b-91ae-364da2661108
Release Notes Vendor Advisory
https://lists.apache.org/thread.html/r210807d0bb55f4aa6fbe1512be6bcc4dacd64e84940429fba329967a%40%3Cusers.httpd.apache.org%3E
Source: af854a3a-2127-422b-91ae-364da2661108
Mailing List
https://lists.apache.org/thread.html/r2eb200ac1340f69aa22af61ab34780c531d110437910cb9c0ece3b37%40%3Cbugs.httpd.apache.org%3E
Source: af854a3a-2127-422b-91ae-364da2661108
Mailing List
https://lists.apache.org/thread.html/r3925e167d5eb1c75def3750c155d753064e1d34a143028bb32910432%40%3Cusers.httpd.apache.org%3E
Source: af854a3a-2127-422b-91ae-364da2661108
Mailing List
https://lists.apache.org/thread.html/r61fdbfc26ab170f4e6492ef3bd5197c20b862ce156e9d5a54d4b899c%40%3Cusers.httpd.apache.org%3E
Source: af854a3a-2127-422b-91ae-364da2661108
Mailing List
https://lists.apache.org/thread.html/r82838efc5fa6fc4c73986399c9b71573589f78b31846aff5bd9b1697%40%3Cusers.httpd.apache.org%3E
Source: af854a3a-2127-422b-91ae-364da2661108
Mailing List
https://lists.apache.org/thread.html/r82c077663f9759c7df5a6656f925b3ee4f55fcd33c889ba7cd687029%40%3Cusers.httpd.apache.org%3E
Source: af854a3a-2127-422b-91ae-364da2661108
Mailing List
https://lists.apache.org/thread.html/rf6954e60b1c8e480678ce3d02f61b8a788997785652e9557a3265c00%40%3Cusers.httpd.apache.org%3E
Source: af854a3a-2127-422b-91ae-364da2661108
Mailing List
https://lists.debian.org/debian-lts-announce/2021/10/msg00001.html
Source: af854a3a-2127-422b-91ae-364da2661108
Mailing List Third Party Advisory
https://lists.fedoraproject.org/archives/list/package-announce%40lists.fedoraproject.org/message/SPBR6WUYBJNACHKE65SPL7TJOHX7RHWD/
Source: af854a3a-2127-422b-91ae-364da2661108
Release Notes
https://lists.fedoraproject.org/archives/list/package-announce%40lists.fedoraproject.org/message/ZNCYSR3BXT36FFF4XTCPL3HDQK4VP45R/
Source: af854a3a-2127-422b-91ae-364da2661108
Release Notes
https://security.gentoo.org/glsa/202208-20
Source: af854a3a-2127-422b-91ae-364da2661108
Third Party Advisory
https://security.netapp.com/advisory/ntap-20211008-0004/
Source: af854a3a-2127-422b-91ae-364da2661108
Third Party Advisory
https://tools.cisco.com/security/center/content/CiscoSecurityAdvisory/cisco-sa-apache-httpd-2.4.49-VWL69sWQ
Source: af854a3a-2127-422b-91ae-364da2661108
Broken Link Third Party Advisory
https://www.debian.org/security/2021/dsa-4982
Source: af854a3a-2127-422b-91ae-364da2661108
Mailing List Third Party Advisory
https://www.oracle.com/security-alerts/cpuapr2022.html
Source: af854a3a-2127-422b-91ae-364da2661108
Patch Third Party Advisory
https://www.oracle.com/security-alerts/cpujan2022.html
Source: af854a3a-2127-422b-91ae-364da2661108
Patch Third Party Advisory
https://www.tenable.com/security/tns-2021-17
Source: af854a3a-2127-422b-91ae-364da2661108
Third Party Advisory
https://www.cisa.gov/known-exploited-vulnerabilities-catalog?field_cve=CVE-2021-40438
Source: 134c704f-9b21-4f2e-91b3-4a467353bcc0
US Government Resource

39 reference(s) from NVD

Quick Stats

CVSS v3 Score
9.0 / 10.0
EPSS (Exploit Probability)
94.4%
100th percentile
Exploitation Status
Actively Exploited
Remediation due: 2021-12-15

Weaknesses (CWE)

CWE-918 CWE-918

Affected Vendors

redhat debian f5 broadcom netapp fedoraproject resf oracle siemens tenable +1 more

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