CVE-2021-40438
mod_proxy SSRF
02 Description
mod_proxy SSRF
03 Exploitation and scoring
- Exploitation
- Exploited in the wild. Listed in the CISA Known Exploited Vulnerabilities catalog on 2021-12-01. Federal remediation due 2021-12-15. Known ransomware campaign use: reported by CISA.
- SSVC decision
- ExploitationactiveCISA reports credible evidence of active exploitation.
- AutomatableyesAn attacker can reliably automate reconnaissance through exploitation, so this scales.
- Technical ImpacttotalSuccessful exploitation gives total control of the vulnerable component.
- EPSS probability
- 99.99% probability of exploitation activity in the next 30 days.
- EPSS percentile
- Equal to or higher than the score of 99.9% of scored records. A rank, not a probability.
- NVD base score
- 9.0 (CVSS v3.x), scored by the NVD independently of the CNA.
- NVD CVSS vector
- CVSS:3.1/AV:N/AC:H/PR:N/UI:N/S:C/C:H/I:H/A:H
- NVD analysis status
- Analyzed. NVD last modified this record on 2026-08-06.
- Red Hat severity
- Important. Red Hat's rating for its own products, not a CVSS rating.
Exploit-prediction scores from FIRST. Independent scoring and analysis status from the NVD. Vendor severity from Red Hat. Exploitation assessment and catalog membership from CISA.
04 Metadata
- Published
- 2021-09-16 14:40Z5 YR AGO
- Last updated
- 2026-08-06 03:55Z2 MO AGO
- Reserved
- 2021-09-02
- Assigning CNA
- apache
- Record state
- PUBLISHED
- Severity
- Critical (CVSS 9.0)
- CNA CVSS vector
- CVSS:3.1/AV:N/AC:H/PR:N/UI:N/S:C/C:H/I:H/A:H
- Weaknesses
- CWE-918Server-Side Request Forgery (SSRF)Base
- Data version
- 5.2
- Document digest
- 2dbb2eaded828c764e5e024921a5b3202db658559398ca3758894f4d973d1d38
05 Affected products
06 References
- httpd.apache.orghttps://httpd.apache.org/security/vulnerabilities_24.html
- lists.fedoraproject.orgFEDORA-2021-dce7e7738ehttps://lists.fedoraproject.org/archives/list/package-announce%40lists.fedoraproject.org/message/SPBR6WUYBJNACHKE65SPL7TJOHX7RHWD/
- lists.apache.org[httpd-users] 20210923 [users@httpd] 2.4.49 security fixes: more infohttps://lists.apache.org/thread.html/r82838efc5fa6fc4c73986399c9b71573589f78b31846aff5bd9b1697%40%3Cusers.httpd.apache.org%3E
- lists.apache.org[httpd-users] 20210923 Re: [users@httpd] 2.4.49 security fixes: more infohttps://lists.apache.org/thread.html/r82c077663f9759c7df5a6656f925b3ee4f55fcd33c889ba7cd687029%40%3Cusers.httpd.apache.org%3E
- lists.apache.org[httpd-users] 20210923 [users@httpd] Re: [External] : [users@httpd] 2.4.49 security fixes: more infohttps://lists.apache.org/thread.html/r3925e167d5eb1c75def3750c155d753064e1d34a143028bb32910432%40%3Cusers.httpd.apache.org%3E
- lists.apache.org[httpd-users] 20210923 Re: [users@httpd] Re: [External] : [users@httpd] 2.4.49 security fixes: more infohttps://lists.apache.org/thread.html/r61fdbfc26ab170f4e6492ef3bd5197c20b862ce156e9d5a54d4b899c%40%3Cusers.httpd.apache.org%3E
- lists.fedoraproject.orgFEDORA-2021-e3f6dd670dhttps://lists.fedoraproject.org/archives/list/package-announce%40lists.fedoraproject.org/message/ZNCYSR3BXT36FFF4XTCPL3HDQK4VP45R/
- lists.debian.org[debian-lts-announce] 20211002 [SECURITY] [DLA 2776-1] apache2 security updatehttps://lists.debian.org/debian-lts-announce/2021/10/msg00001.html
- lists.apache.org[httpd-bugs] 20211008 [Bug 65616] CVE-2021-36160 regressionhttps://lists.apache.org/thread.html/r2eb200ac1340f69aa22af61ab34780c531d110437910cb9c0ece3b37%40%3Cbugs.httpd.apache.org%3E
- www.debian.orgDSA-4982https://www.debian.org/security/2021/dsa-4982
- lists.apache.org[httpd-users] 20211019 [users@httpd] Regarding CVE-2021-40438https://lists.apache.org/thread.html/r210807d0bb55f4aa6fbe1512be6bcc4dacd64e84940429fba329967a%40%3Cusers.httpd.apache.org%3E
- lists.apache.org[httpd-users] 20211019 Re: [users@httpd] Regarding CVE-2021-40438https://lists.apache.org/thread.html/rf6954e60b1c8e480678ce3d02f61b8a788997785652e9557a3265c00%40%3Cusers.httpd.apache.org%3E
- tools.cisco.com20211124 Multiple Vulnerabilities in Apache HTTP Server Affecting Cisco Products: November 2021https://tools.cisco.com/security/center/content/CiscoSecurityAdvisory/cisco-sa-apache-httpd-2.4.49-VWL69sWQ
- www.oracle.comhttps://www.oracle.com/security-alerts/cpujan2022.html
- www.tenable.comhttps://www.tenable.com/security/tns-2021-17
- security.netapp.comhttps://security.netapp.com/advisory/ntap-20211008-0004/
- www.oracle.comhttps://www.oracle.com/security-alerts/cpuapr2022.html
- cert-portal.siemens.comhttps://cert-portal.siemens.com/productcert/pdf/ssa-685781.pdf
- security.gentoo.orgGLSA-202208-20https://security.gentoo.org/glsa/202208-20
- www.cisa.govhttps://www.cisa.gov/known-exploited-vulnerabilities-catalog?field_cve=CVE-2021-40438
07 Fixed in
AlmaLinux 8
- httpd Fixed in 2.4.37-43.module_el8.5.0+2597+c4b14997.alma
- httpd-devel Fixed in 2.4.37-43.module_el8.5.0+2597+c4b14997.alma
- httpd-filesystem Fixed in 2.4.37-43.module_el8.5.0+2597+c4b14997.alma
- httpd-manual Fixed in 2.4.37-43.module_el8.5.0+2597+c4b14997.alma
- httpd-tools Fixed in 2.4.37-43.module_el8.5.0+2597+c4b14997.alma
- mod_http2 Fixed in 1.15.7-3.module_el8.5.0+2609+b30d9eec
- mod_ldap Fixed in 2.4.37-43.module_el8.5.0+2597+c4b14997.alma
- mod_md Fixed
A version is affected if any line below covers it.
- Affected before 1:2.0.8-8.module_el8.5.0+2609+b30d9eec
- Affected before 1:2.0.8-8.module_el8.6.0+2872+fe0ff7aa
- mod_proxy_html Fixed in 1:2.4.37-43.module_el8.5.0+2597+c4b14997.alma
- mod_session Fixed in 2.4.37-43.module_el8.5.0+2597+c4b14997.alma
- mod_ssl Fixed in 1:2.4.37-43.module_el8.5.0+2597+c4b14997.alma
Source: AlmaLinux, AlmaLinux OS. Copyright (c) 2023 AlmaLinux OS. Licensed under MIT License. Received through OSV.dev. Reformatted by exploit.cc.
Arch Linux
- apache Fixed in 2.4.49-1
Source: Arch Linux Security Tracker, the Arch Linux security team. Reformatted by exploit.cc.
CloudLinux 8
- httpd Fixed in 2.4.37-43.module_el8.5.0+2597+c4b14997.alma
- httpd-devel Fixed in 2.4.37-43.module_el8.5.0+2597+c4b14997.alma
- httpd-filesystem Fixed in 2.4.37-43.module_el8.5.0+2597+c4b14997.alma
- httpd-manual Fixed in 2.4.37-43.module_el8.5.0+2597+c4b14997.alma
- httpd-tools Fixed in 2.4.37-43.module_el8.5.0+2597+c4b14997.alma
- mod_http2 Fixed in 1.15.7-3.module_el8.5.0+2609+b30d9eec
- mod_ldap Fixed in 2.4.37-43.module_el8.5.0+2597+c4b14997.alma
- mod_md Fixed
A version is affected if any line below covers it.
- Affected before 1:2.0.8-8.module_el8.5.0+2609+b30d9eec
- Affected before 1:2.0.8-8.module_el8.6.0+2872+fe0ff7aa
- mod_proxy_html Fixed in 1:2.4.37-43.module_el8.5.0+2597+c4b14997.alma
- mod_session Fixed in 2.4.37-43.module_el8.5.0+2597+c4b14997.alma
- mod_ssl Fixed in 1:2.4.37-43.module_el8.5.0+2597+c4b14997.alma
Derived from AlmaLinux 8. Partial coverage: only packages taken from AlmaLinux 8 are listed.
Source: CloudLinux errata, CloudLinux Inc. Derived from: AlmaLinux, AlmaLinux OS. Copyright (c) 2023 AlmaLinux OS. Licensed under MIT License. Received through OSV.dev. Reformatted by exploit.cc.
Debian 12
- apache2 Fixed in 2.4.49-1
Source: Debian Security Tracker, the Debian security team. Received through OSV.dev. Reformatted by exploit.cc.
Debian 13
- apache2 Fixed in 2.4.49-1
Source: Debian Security Tracker, the Debian security team. Received through OSV.dev. Reformatted by exploit.cc.
Debian 14
- apache2 Fixed in 2.4.49-1
Source: Debian Security Tracker, the Debian security team. Received through OSV.dev. Reformatted by exploit.cc.
Ubuntu 18.04 LTS
- apache2 Fixed in 2.4.29-1ubuntu4.18
Source: Ubuntu, Canonical Ltd. Licensed under CC BY-SA 4.0. Received through OSV.dev. Reformatted by exploit.cc.
Ubuntu 20.04 LTS
- apache2 Fixed in 2.4.41-4ubuntu3.6
Source: Ubuntu, Canonical Ltd. Licensed under CC BY-SA 4.0. Received through OSV.dev. Reformatted by exploit.cc.
Ubuntu Pro 16.04 LTS
- apache2 Fixed in 2.4.18-2ubuntu3.17+esm3Available with Ubuntu Pro (Infra-only): https://ubuntu.com/pro
Source: Ubuntu, Canonical Ltd. Licensed under CC BY-SA 4.0. Received through OSV.dev. Reformatted by exploit.cc.
A release or ecosystem missing from this list has no record here. It may be unaffected or not covered by the source. Source notices and licences.