CVE-2021-40438

Act now ● On CISA KEV — actively exploited used in ransomware

Actively exploited — on the CISA KEV list.

CVSS base

9.0 CRITICAL

CVSS:3.1/AV:N/AC:H/PR:N/UI:N/S:C/C:H/I:H/A:H

EPSS — probability of exploitation (30 days)

100.0%

100.0th percentile

CISA KEV

Listed

Added 2021-12-01 · patch by 2021-12-15

Weakness / dates

CWE-918

Published 2021-09-16 · modified 2026-08-06

CVSS breakdown

CVSS:3.1/AV:N/AC:H/PR:N/UI:N/S:C/C:H/I:H/A:H

Attack Vector	N	Network
Attack Complexity	H	High
Privileges Required	N	None
User Interaction	N	None
Scope	C	Changed
Confidentiality	H	High
Integrity	H	High
Availability	H	High

Timeline

2021-09-16 — Published (NVD)
2021-12-01 — Added to CISA KEV (actively exploited)
2021-12-15 — CISA patch-by deadline
2026-08-06 — Last modified (NVD)

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.

Affected

apache broadcom debian f5 fedoraproject netapp oracle redhat resf siemens tenable

References

Official: NVD · CVE.org