--- title: "CVE-2021-40438: mod_proxy SSRF | CubePath" 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…" language: en source: https://cubepath.com/security/cve/CVE-2021-40438 --- # CVE-2021-40438: mod_proxy SSRF | CubePath ## 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. Official description from the CVE record, published by apache. Copyright © 1999-2026 The MITRE Corporation. See [/security/cve/legal](https://cubepath.com/security/cve/legal) for the CVE license. [View the record on cve.org](https://www.cve.org/CVERecord?id=CVE-2021-40438) ## Key data ### CVSS 3.1 Critical 9.0 Score published by CISA-ADP in the CVE record. CVSS:3.1/AV:N/AC:H/PR:N/UI:N/S:C/C:H/I:H/A:H | Metric | Value | What it means | | ---------------------- | ------- | ----------------------------------------------------------------------------------------- | | Attack vector | Network | The vulnerable component can be reached over a network, possibly from the Internet. | | Attack complexity | High | The attack depends on conditions outside the attacker's control, so it takes preparation. | | Privileges required | None | No account or privileges are needed. | | User interaction | None | No action from any user is needed. | | Scope | Changed | The impact can reach other components beyond the vulnerable one. | | Confidentiality impact | High | Serious or total effect on the secrecy of data. | | Integrity impact | High | Serious or total effect on the trustworthiness of data. | | Availability impact | High | Serious or total effect on availability. | CVSS is owned and managed by FIRST.Org, Inc. (FIRST) and is used by permission. Each CVSS score on this site is shown together with its vector string, as published in the CVE record by the source named next to it. Learn more at [first.org/cvss](https://www.first.org/cvss/) . ### EPSS Exploit Prediction Scoring System by FIRST: an estimate of the probability that exploitation activity will be observed in the next 30 days. Score 0.99999 (99.99% probability) Percentile 99.99% Scores of Nov 10, 2026 Model v2026.06.15 ### CISA Known Exploited Vulnerabilities This CVE is listed in the CISA KEV catalog. Name in the catalog Apache HTTP Server-Side Request Forgery (SSRF) Added to the catalog Dec 1, 2021 Federal due date Dec 15, 2021 Ransomware campaigns Known use ### CISA assessment as of Oct 14, 2021 Stakeholder-Specific Vulnerability Categorization (SSVC) decision points added by CISA. Exploitation Recorded by CISA as active Automatable yes Technical impact total ### Weakness (CWE) CWE catalog version 5.0. CWE names: Copyright © 2006-2026, The MITRE Corporation. See [/security/cve/legal](https://cubepath.com/security/cve/legal) for the CWE license. - [CWE-918](https://cwe.mitre.org/data/definitions/918.html) Server-Side Request Forgery ## Affected products Products listed in the CVE record, as the CNA published them. - Apache HTTP Server - affected: Apache HTTP Server 2.4 up to 2.4.48 ## References Links listed in the CVE record. They lead to other sites, which CubePath does not control. - [httpd.apache.org/security/vulnerabilities\_24.html](https://httpd.apache.org/security/vulnerabilities%5F24.html) - [FEDORA-2021-dce7e7738e](https://lists.fedoraproject.org/archives/list/package-announce%40lists.fedoraproject.org/message/SPBR6WUYBJNACHKE65SPL7TJOHX7RHWD/) (lists.fedoraproject.org) vendor-advisory - [\[httpd-users\] 20210923 \[users@httpd\] 2.4.49 security fixes: more info](https://lists.apache.org/thread.html/r82838efc5fa6fc4c73986399c9b71573589f78b31846aff5bd9b1697%40%3Cusers.httpd.apache.org%3E) (lists.apache.org) mailing-list - [\[httpd-users\] 20210923 Re: \[users@httpd\] 2.4.49 security fixes: more info](https://lists.apache.org/thread.html/r82c077663f9759c7df5a6656f925b3ee4f55fcd33c889ba7cd687029%40%3Cusers.httpd.apache.org%3E) (lists.apache.org) mailing-list - [\[httpd-users\] 20210923 \[users@httpd\] Re: \[External\] : \[users@httpd\] 2.4.49 security fixes: more info](https://lists.apache.org/thread.html/r3925e167d5eb1c75def3750c155d753064e1d34a143028bb32910432%40%3Cusers.httpd.apache.org%3E) (lists.apache.org) mailing-list - [\[httpd-users\] 20210923 Re: \[users@httpd\] Re: \[External\] : \[users@httpd\] 2.4.49 security fixes: more info](https://lists.apache.org/thread.html/r61fdbfc26ab170f4e6492ef3bd5197c20b862ce156e9d5a54d4b899c%40%3Cusers.httpd.apache.org%3E) (lists.apache.org) mailing-list - [FEDORA-2021-e3f6dd670d](https://lists.fedoraproject.org/archives/list/package-announce%40lists.fedoraproject.org/message/ZNCYSR3BXT36FFF4XTCPL3HDQK4VP45R/) (lists.fedoraproject.org) vendor-advisory - [\[debian-lts-announce\] 20211002 \[SECURITY\] \[DLA 2776-1\] apache2 security update](https://lists.debian.org/debian-lts-announce/2021/10/msg00001.html) (lists.debian.org) mailing-list - [\[httpd-bugs\] 20211008 \[Bug 65616\] CVE-2021-36160 regression](https://lists.apache.org/thread.html/r2eb200ac1340f69aa22af61ab34780c531d110437910cb9c0ece3b37%40%3Cbugs.httpd.apache.org%3E) (lists.apache.org) mailing-list - [DSA-4982](https://www.debian.org/security/2021/dsa-4982) (debian.org) vendor-advisory - [\[httpd-users\] 20211019 \[users@httpd\] Regarding CVE-2021-40438](https://lists.apache.org/thread.html/r210807d0bb55f4aa6fbe1512be6bcc4dacd64e84940429fba329967a%40%3Cusers.httpd.apache.org%3E) (lists.apache.org) mailing-list - [\[httpd-users\] 20211019 Re: \[users@httpd\] Regarding CVE-2021-40438](https://lists.apache.org/thread.html/rf6954e60b1c8e480678ce3d02f61b8a788997785652e9557a3265c00%40%3Cusers.httpd.apache.org%3E) (lists.apache.org) mailing-list - [20211124 Multiple Vulnerabilities in Apache HTTP Server Affecting Cisco Products: November 2021](https://tools.cisco.com/security/center/content/CiscoSecurityAdvisory/cisco-sa-apache-httpd-2.4.49-VWL69sWQ) (tools.cisco.com) vendor-advisory - [oracle.com/security-alerts/cpujan2022.html](https://www.oracle.com/security-alerts/cpujan2022.html) - [tenable.com/security/tns-2021-17](https://www.tenable.com/security/tns-2021-17) - [security.netapp.com/advisory/ntap-20211008-0004](https://security.netapp.com/advisory/ntap-20211008-0004/) - [oracle.com/security-alerts/cpuapr2022.html](https://www.oracle.com/security-alerts/cpuapr2022.html) - [cert-portal.siemens.com/productcert/pdf/ssa-685781.pdf](https://cert-portal.siemens.com/productcert/pdf/ssa-685781.pdf) - [GLSA-202208-20](https://security.gentoo.org/glsa/202208-20) (security.gentoo.org) vendor-advisory ## Timeline 1. ID reserved Sep 2, 2021 2. Record published Sep 16, 2021 3. Added to CISA KEV Dec 1, 2021 4. Record last updated Aug 6, 2026 ## Look up another CVE ## About CubePath CubePath is a cloud provider with data centers in Europe and the United States. It offers VPS, bare metal servers and DDoS protection. [Cloud VPS](https://cubepath.com/vps) [DDoS protection](https://cubepath.com/ddos-protection) Data from the CVE Program (MITRE), CISA KEV and FIRST EPSS. CVSS is owned by FIRST and used by permission. Not affiliated with or endorsed by MITRE, CISA or FIRST. Data as of Nov 10, 2026, 20:04 UTC. [Sources and licenses](https://cubepath.com/security/cve/legal)