CVE-2021-40438
Apache Software Foundation Apache HTTP Server
Published 16 Sept 2021 · updated 6 Aug 2026 · Analyzed
9.0 Critical · CVSS 3.1, NVD
Exploited in the wild
CISA added this to its Known Exploited Vulnerabilities catalog on 1 Dec 2021, with a remediation deadline of 15 Dec 2021 for US federal agencies. It has been used in ransomware campaigns.
Required action: Apply updates per vendor instructions.
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.
References
- cert-portal.siemens.com/productcert/pdf/ssa-685781.pdf · Third Party Advisory
- httpd.apache.org/security/vulnerabilities_24.html · Release Notes, Vendor Advisory
- lists.apache.org/thread.html/r210807d0bb55f4aa6fbe1512be6bcc4dacd64e84940429fba329967a%40%3Cusers.httpd.apache.org%3E · Mailing List
- lists.apache.org/thread.html/r2eb200ac1340f69aa22af61ab34780c531d110437910cb9c0ece3b37%40%3Cbugs.httpd.apache.org%3E · Mailing List
- lists.apache.org/thread.html/r3925e167d5eb1c75def3750c155d753064e1d34a143028bb32910432%40%3Cusers.httpd.apache.org%3E · Mailing List
- lists.apache.org/thread.html/r61fdbfc26ab170f4e6492ef3bd5197c20b862ce156e9d5a54d4b899c%40%3Cusers.httpd.apache.org%3E · Mailing List
- lists.apache.org/thread.html/r82838efc5fa6fc4c73986399c9b71573589f78b31846aff5bd9b1697%40%3Cusers.httpd.apache.org%3E · Mailing List
- lists.apache.org/thread.html/r82c077663f9759c7df5a6656f925b3ee4f55fcd33c889ba7cd687029%40%3Cusers.httpd.apache.org%3E · Mailing List
- lists.apache.org/thread.html/rf6954e60b1c8e480678ce3d02f61b8a788997785652e9557a3265c00%40%3Cusers.httpd.apache.org%3E · Mailing List
- lists.debian.org/debian-lts-announce/2021/10/msg00001.html · Mailing List, Third Party Advisory
- lists.fedoraproject.org/archives/list/package-announce%40lists.fedoraproject.org/message/SPBR6WUYBJNACHKE65SPL7TJOHX7RHWD/ · Release Notes
- lists.fedoraproject.org/archives/list/package-announce%40lists.fedoraproject.org/message/ZNCYSR3BXT36FFF4XTCPL3HDQK4VP45R/ · Release Notes
- security.gentoo.org/glsa/202208-20 · Third Party Advisory
- security.netapp.com/advisory/ntap-20211008-0004/ · Third Party Advisory
- tools.cisco.com/security/center/content/CiscoSecurityAdvisory/cisco-sa-apache-httpd-2.4.49-VWL69sWQ · Broken Link, Third Party Advisory
- www.debian.org/security/2021/dsa-4982 · Mailing List, Third Party Advisory
- www.oracle.com/security-alerts/cpuapr2022.html · Patch, Third Party Advisory
- www.oracle.com/security-alerts/cpujan2022.html · Patch, Third Party Advisory
- www.tenable.com/security/tns-2021-17 · Third Party Advisory
- www.cisa.gov/known-exploited-vulnerabilities-catalog?field_cve=CVE-2021-40438 · US Government Resource