VulnerabilityAnalyzed
CVE-2021-40438
Apache HTTP Server-Side Request Forgery (SSRF)
KEVCRITICAL 9.0EPSS 100.0%
Does this matter?
Known to be exploited in the wild (CISA KEV, CISA remediation deadline 15 December 2021). Treat as an emergency change: patch or isolate now, then hunt for prior compromise.
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.
- CVSS 3.1
- 9.0 CRITICALCVSS:3.1/AV:N/AC:H/PR:N/UI:N/S:C/C:H/I:H/A:H
- EPSS
- 100.00% probability · 100th percentile
- Public exploits
- None in Exploit-DB
- CISA KEV
- Listed 1 December 2021 · due 15 December 2021 · used in ransomware campaigns
- Weakness
- CWE-918
- Affected
- resf/rocky linux · redhat/enterprise linux · redhat/enterprise linux eus · redhat/enterprise linux for arm 64 · redhat/enterprise linux for arm 64 eus · redhat/enterprise linux for ibm z systems · redhat/enterprise linux for ibm z systems eus · redhat/enterprise linux for ibm z systems eus s390x · redhat/enterprise linux for power big endian · redhat/enterprise linux for power little endian · redhat/enterprise linux for power little endian eus · redhat/enterprise linux for scientific computing · redhat/enterprise linux server · redhat/enterprise linux server aus · redhat/enterprise linux server for power little endian update services for sap solutions · redhat/enterprise linux server tus · redhat/enterprise linux server update services for sap solutions · redhat/enterprise linux update services for sap solutions · redhat/enterprise linux workstation · redhat/jboss core services · +19 more
- Source
- security@apache.org
EPSS 100.0% since 30 October 2026; no change recorded yet. The dashed line is the ten per cent mark our analysts treat as “patch before the next change window”. Points are recorded when the score first appears and whenever it moves by a percentage point or more.
CISA notes
Apply updates per vendor instructions. https://nvd.nist.gov/vuln/detail/CVE-2021-40438
References
- https://cert-portal.siemens.com/productcert/pdf/ssa-685781.pdfThird Party Advisory
- https://httpd.apache.org/security/vulnerabilities_24.htmlRelease Notes, Vendor Advisory
- https://lists.apache.org/thread.html/r210807d0bb55f4aa6fbe1512be6bcc4dacd64e84940429fba329967a%40%3Cusers.httpd.apache.org%3EMailing List
- https://lists.apache.org/thread.html/r2eb200ac1340f69aa22af61ab34780c531d110437910cb9c0ece3b37%40%3Cbugs.httpd.apache.org%3EMailing List
- https://lists.apache.org/thread.html/r3925e167d5eb1c75def3750c155d753064e1d34a143028bb32910432%40%3Cusers.httpd.apache.org%3EMailing List
- https://lists.apache.org/thread.html/r61fdbfc26ab170f4e6492ef3bd5197c20b862ce156e9d5a54d4b899c%40%3Cusers.httpd.apache.org%3EMailing List
- https://lists.apache.org/thread.html/r82838efc5fa6fc4c73986399c9b71573589f78b31846aff5bd9b1697%40%3Cusers.httpd.apache.org%3EMailing List
- https://lists.apache.org/thread.html/r82c077663f9759c7df5a6656f925b3ee4f55fcd33c889ba7cd687029%40%3Cusers.httpd.apache.org%3EMailing List
- https://lists.apache.org/thread.html/rf6954e60b1c8e480678ce3d02f61b8a788997785652e9557a3265c00%40%3Cusers.httpd.apache.org%3EMailing List
- https://lists.debian.org/debian-lts-announce/2021/10/msg00001.htmlMailing 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/202208-20Third 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-VWL69sWQBroken Link, Third Party Advisory
- https://www.debian.org/security/2021/dsa-4982Mailing List, Third Party Advisory
- https://www.oracle.com/security-alerts/cpuapr2022.htmlPatch, Third Party Advisory
- https://www.oracle.com/security-alerts/cpujan2022.htmlPatch, Third Party Advisory
- https://www.tenable.com/security/tns-2021-17Third Party Advisory
- https://cert-portal.siemens.com/productcert/pdf/ssa-685781.pdfThird Party Advisory
- https://httpd.apache.org/security/vulnerabilities_24.htmlRelease Notes, Vendor Advisory
- https://lists.apache.org/thread.html/r210807d0bb55f4aa6fbe1512be6bcc4dacd64e84940429fba329967a%40%3Cusers.httpd.apache.org%3EMailing List
- https://lists.apache.org/thread.html/r2eb200ac1340f69aa22af61ab34780c531d110437910cb9c0ece3b37%40%3Cbugs.httpd.apache.org%3EMailing List
- https://lists.apache.org/thread.html/r3925e167d5eb1c75def3750c155d753064e1d34a143028bb32910432%40%3Cusers.httpd.apache.org%3EMailing List
- https://lists.apache.org/thread.html/r61fdbfc26ab170f4e6492ef3bd5197c20b862ce156e9d5a54d4b899c%40%3Cusers.httpd.apache.org%3EMailing List
- https://lists.apache.org/thread.html/r82838efc5fa6fc4c73986399c9b71573589f78b31846aff5bd9b1697%40%3Cusers.httpd.apache.org%3EMailing List
- https://lists.apache.org/thread.html/r82c077663f9759c7df5a6656f925b3ee4f55fcd33c889ba7cd687029%40%3Cusers.httpd.apache.org%3EMailing List
- https://lists.apache.org/thread.html/rf6954e60b1c8e480678ce3d02f61b8a788997785652e9557a3265c00%40%3Cusers.httpd.apache.org%3EMailing List
- https://lists.debian.org/debian-lts-announce/2021/10/msg00001.htmlMailing List, Third Party Advisory
- https://lists.fedoraproject.org/archives/list/package-announce%40lists.fedoraproject.org/message/SPBR6WUYBJNACHKE65SPL7TJOHX7RHWD/Release Notes
Source: NVD record, EPSS from FIRST.org, KEV from CISA, exploits from Exploit-DB. Refreshed daily. Download this record as JSON.