# CVE-2021-40438: mod_proxy SSRF

> CVE-2021-40438: mod_proxy SSRF. CVSS 9.0 (CVSS 3.1), in CISA KEV.

Canonical: https://rewindex.com/cve/CVE-2021-40438
Last updated: 2026-08-06T03:55:20Z

- Published: 2021-09-16 14:40 UTC · Updated: 2026-08-06 03:55 UTC · Assigner: apache
- CVSS: 9.0 (CVSS 3.1) · Severity: Critical · Vector: CVSS:3.1/AV:N/AC:H/PR:N/UI:N/S:C/C:H/I:H/A:H
- EPSS: 100.0%, 100th percentile (scored 2026-10-25)
- CISA KEV: yes, added 2021-12-01, federal due date 2021-12-15, ransomware use: Known
- CWE: CWE-918

## 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.

## CISA required action

Apply updates per vendor instructions.

## Affected vendors and products

- Apache Software Foundation: Apache HTTP Server

## References

- [CVE record on cve.org](https://www.cve.org/CVERecord?id=CVE-2021-40438)
- [NVD entry](https://nvd.nist.gov/vuln/detail/CVE-2021-40438)
- [https://cert-portal.siemens.com/productcert/pdf/ssa-685781.pdf](https://cert-portal.siemens.com/productcert/pdf/ssa-685781.pdf)
- [https://httpd.apache.org/security/vulnerabilities\_24.html](https://httpd.apache.org/security/vulnerabilities_24.html)
- [https://lists.apache.org/thread.html/r210807d0bb55f4aa6fbe1512be6bcc4dacd64e84940429fba329967a%40%3Cusers.httpd.apache.org%3E](https://lists.apache.org/thread.html/r210807d0bb55f4aa6fbe1512be6bcc4dacd64e84940429fba329967a%2540%3Cusers.httpd.apache.org%3E)
- [https://lists.apache.org/thread.html/r2eb200ac1340f69aa22af61ab34780c531d110437910cb9c0ece3b37%40%3Cbugs.httpd.apache.org%3E](https://lists.apache.org/thread.html/r2eb200ac1340f69aa22af61ab34780c531d110437910cb9c0ece3b37%2540%3Cbugs.httpd.apache.org%3E)
- [https://lists.apache.org/thread.html/r3925e167d5eb1c75def3750c155d753064e1d34a143028bb32910432%40%3Cusers.httpd.apache.org%3E](https://lists.apache.org/thread.html/r3925e167d5eb1c75def3750c155d753064e1d34a143028bb32910432%2540%3Cusers.httpd.apache.org%3E)
- [https://lists.apache.org/thread.html/r61fdbfc26ab170f4e6492ef3bd5197c20b862ce156e9d5a54d4b899c%40%3Cusers.httpd.apache.org%3E](https://lists.apache.org/thread.html/r61fdbfc26ab170f4e6492ef3bd5197c20b862ce156e9d5a54d4b899c%2540%3Cusers.httpd.apache.org%3E)
- [https://lists.apache.org/thread.html/r82838efc5fa6fc4c73986399c9b71573589f78b31846aff5bd9b1697%40%3Cusers.httpd.apache.org%3E](https://lists.apache.org/thread.html/r82838efc5fa6fc4c73986399c9b71573589f78b31846aff5bd9b1697%2540%3Cusers.httpd.apache.org%3E)
- [https://lists.apache.org/thread.html/r82c077663f9759c7df5a6656f925b3ee4f55fcd33c889ba7cd687029%40%3Cusers.httpd.apache.org%3E](https://lists.apache.org/thread.html/r82c077663f9759c7df5a6656f925b3ee4f55fcd33c889ba7cd687029%2540%3Cusers.httpd.apache.org%3E)
- [https://lists.apache.org/thread.html/rf6954e60b1c8e480678ce3d02f61b8a788997785652e9557a3265c00%40%3Cusers.httpd.apache.org%3E](https://lists.apache.org/thread.html/rf6954e60b1c8e480678ce3d02f61b8a788997785652e9557a3265c00%2540%3Cusers.httpd.apache.org%3E)
- [https://lists.debian.org/debian-lts-announce/2021/10/msg00001.html](https://lists.debian.org/debian-lts-announce/2021/10/msg00001.html)
- [https://lists.fedoraproject.org/archives/list/package-announce%40lists.fedoraproject.org/message/SPBR6WUYBJNACHKE65SPL7TJOHX7RHWD/](https://lists.fedoraproject.org/archives/list/package-announce%2540lists.fedoraproject.org/message/SPBR6WUYBJNACHKE65SPL7TJOHX7RHWD/)
- [https://lists.fedoraproject.org/archives/list/package-announce%40lists.fedoraproject.org/message/ZNCYSR3BXT36FFF4XTCPL3HDQK4VP45R/](https://lists.fedoraproject.org/archives/list/package-announce%2540lists.fedoraproject.org/message/ZNCYSR3BXT36FFF4XTCPL3HDQK4VP45R/)
- [https://security.gentoo.org/glsa/202208-20](https://security.gentoo.org/glsa/202208-20)
- [https://security.netapp.com/advisory/ntap-20211008-0004/](https://security.netapp.com/advisory/ntap-20211008-0004/)
- [https://tools.cisco.com/security/center/content/CiscoSecurityAdvisory/cisco-sa-apache-httpd-2.4.49-VWL69sWQ](https://tools.cisco.com/security/center/content/CiscoSecurityAdvisory/cisco-sa-apache-httpd-2.4.49-VWL69sWQ)
- [https://www.debian.org/security/2021/dsa-4982](https://www.debian.org/security/2021/dsa-4982)
- [https://www.oracle.com/security-alerts/cpuapr2022.html](https://www.oracle.com/security-alerts/cpuapr2022.html)
- [https://www.oracle.com/security-alerts/cpujan2022.html](https://www.oracle.com/security-alerts/cpujan2022.html)
- [https://www.tenable.com/security/tns-2021-17](https://www.tenable.com/security/tns-2021-17)

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_Sources: CVE records from the CVE Program (cve.org). CVE® is a registered trademark of The MITRE Corporation. (https://www.cve.org/) This product uses data from the NVD API but is not endorsed or certified by the NVD. (https://nvd.nist.gov/) Known Exploited Vulnerabilities catalog from CISA. (https://www.cisa.gov/known-exploited-vulnerabilities-catalog) EPSS scores from FIRST (Exploit Prediction Scoring System). (https://www.first.org/epss/)_


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Canonical: https://rewindex.com/cve/CVE-2021-40438 · Markdown: https://rewindex.com/cve/CVE-2021-40438.md · JSON: https://rewindex.com/api/v1/cves/CVE-2021-40438 · Data licensed CC BY 4.0 (https://creativecommons.org/licenses/by/4.0/) · Generated 2026-10-26T03:12:43.573Z