CVE-2021-41773

CRITICAL9.8

CISA KEV

Published 2021-10-05 · Updated 2026-06-17 · Source security@apache.org

Summary

CVE-2021-41773 is a critical-severity (CVSS 9.8) vulnerability in Apache HTTP Server. CISA added it to the Known Exploited Vulnerabilities catalog on November 3, 2021, which means exploitation in the wild has been confirmed; US federal agencies had to remediate it by November 17, 2021. CISA also lists it as known to be used in ransomware campaigns, so it should be prioritised accordingly. Apache has 41 vulnerabilities in the KEV catalog, 8 of them linked to ransomware.

All 41 known-exploited Apache vulnerabilities →

Description

A flaw was found in a change made to path normalization in Apache HTTP Server 2.4.49. An attacker could use a path traversal attack to map URLs to files outside the directories configured by Alias-like directives. If files outside of these directories are not protected by the usual default configuration "require all denied", these requests can succeed. If CGI scripts are also enabled for these aliased pathes, this could allow for remote code execution. This issue is known to be exploited in the wild. This issue only affects Apache 2.4.49 and not earlier versions. The fix in Apache HTTP Server 2.4.50 was found to be incomplete, see CVE-2021-42013.

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

CWE-22CWE-22

CISA Known-Exploited Vulnerability

Product: Apache — HTTP Server

Name: Apache HTTP Server Path Traversal Vulnerability

Date added: 2021-11-03 · Due: 2021-11-17

USED IN RANSOMWARE

Required action: Apply updates per vendor instructions.

References

View on NVD

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