Critical severity · published Sep 16, 2021
CVE-2021-40438
mod_proxy SSRF
RansomwareIn wildKEV
9.0
CVSS
100%
EPSS
Yes
On KEV
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 vector
CVSS:3.1/AV:N/AC:H/PR:N/UI:N/S:C/C:H/I:H/A:H
Attack vector
Network
Complexity
High
Privileges
None
User interaction
None
Confidentiality
High
Integrity
High
Availability
High
Scope
Changed
Exploitation
Is it being used?
Exploit prediction (EPSS)100.0% · higher than 100% of CVEs
Exploited in the wildYes
CISA KEVListed Dec 1, 2021
Federal remediation dueDec 15, 2021
Ransomware campaign useKnown
Affected products
Which versions
HS
HTTP Server · Apache
Apache HTTP Server 2.4 through 2.4.48 · source: vendor, NVD
BF
Brocade Fabric Operating System Firmware · Broadcom
All versions, or not specified · source: NVD
CB
Cloud Backup · Netapp
All versions, or not specified · source: NVD
CD
Clustered Data Ontap · Netapp
All versions, or not specified · source: NVD
DL
Debian Linux · Debian
9.0; 10.0; 11.0 · source: NVD
EL
Enterprise Linux · Redhat
8.0 · source: NVD
EL
Enterprise Linux Eus · Redhat
8.1; 8.2; 8.4; 8.6; 8.8 · source: NVD
EL
Enterprise Linux For Arm 64 · Redhat
8.0 · source: NVD
EL
Enterprise Linux For Arm 64 Eus · Redhat
8.6; 8.8 · source: NVD
EL
Enterprise Linux For Ibm Z Systems · Redhat
7.0_s390x; 8.0 · source: NVD
EL
Enterprise Linux For Ibm Z Systems Eus · Redhat
8.1; 8.4; 8.8 · source: NVD
EL
Enterprise Linux For Ibm Z Systems Eus S390x · Redhat
8.2 · source: NVD
References
NVD
https://nvd.nist.gov/vuln/detail/CVE-2021-40438
CVE.org
https://www.cve.org/CVERecord?id=CVE-2021-40438
CISA KEV catalogue
https://www.cisa.gov/known-exploited-vulnerabilities-catalog
x_refsource_MISC
https://httpd.apache.org/security/vulnerabilities_24.html
vendor-advisory
https://lists.fedoraproject.org/archives/list/package-announce%40lists.fedoraproject.org/message/SPBR6WUYBJNACHKE65SPL7TJOHX7RHWD/
mailing-list
https://lists.apache.org/thread.html/r82838efc5fa6fc4c73986399c9b71573589f78b31846aff5bd9b1697%40%3Cusers.httpd.apache.org%3E
mailing-list
https://lists.apache.org/thread.html/r82c077663f9759c7df5a6656f925b3ee4f55fcd33c889ba7cd687029%40%3Cusers.httpd.apache.org%3E
mailing-list
https://lists.apache.org/thread.html/r3925e167d5eb1c75def3750c155d753064e1d34a143028bb32910432%40%3Cusers.httpd.apache.org%3E
mailing-list
https://lists.apache.org/thread.html/r61fdbfc26ab170f4e6492ef3bd5197c20b862ce156e9d5a54d4b899c%40%3Cusers.httpd.apache.org%3E
More from HTTP Server
9.8
CVE-2021-42013
Path Traversal and Remote Code Execution in Apache HTTP Server 2.4.49 and 2.4.50 (incomplete fix of CVE-2021-41773)
9.8
CVE-2021-41773
Path traversal and file disclosure vulnerability in Apache HTTP Server 2.4.49
9.1
CVE-2024-38475
Apache HTTP Server weakness in mod_rewrite when first segment of substitution matches filesystem path.
7.8
CVE-2019-0211
Apache HTTP Server Privilege Escalation Vulnerability
9.8
CVE-2026-59797
Apache HTTP Server: mod_ssl SSLRequire allows .htaccess ap_expr file-function