CVE-2021-40438
CVSS v3
9
CRITICAL
EPSS Score
94.4 %
exploit probability
CISA KEV
Yes
known exploited
Exploitation
—
SSVC status
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 Known Exploited Vulnerability
- Date Added
- 2021-12-01
- Patch Due Date
- 2021-12-15
- Ransomware Use
- Unknown
Technical details
- CVSS v3 Vector
- CVSS:3.1/AV:N/AC:H/PR:N/UI:N/S:C/C:H/I:H/A:H
- Published
- 2021-09-16
- Last Modified
- 2026-08-05
Frequently asked questions
What is CVE-2021-40438?
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.
Is CVE-2021-40438 actively exploited?
Yes. CVE-2021-40438 is on the CISA Known Exploited Vulnerabilities (KEV) catalog, meaning it has been confirmed as actively exploited in the wild. CISA requires federal agencies to patch by 12/15/2021.
What is the CVSS score for CVE-2021-40438?
CVE-2021-40438 has a CVSS v3 base score of 9 (CRITICAL severity), with vector string CVSS:3.1/AV:N/AC:H/PR:N/UI:N/S:C/C:H/I:H/A:H.
Is CVE-2021-40438 affecting your environment?
Use isMalicious to check if any of your IPs or domains are associated with this vulnerability's IOCs.
No credit card required · 30 free checks/month · Free API key
Other 2021 vulnerabilities worth triaging
Ranked by exploit probability (EPSS).