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CVE-2021-41773

Path traversal and file disclosure vulnerability in Apache HTTP Server 2.4.49

  • High 7.5
  • Exploited: added to CISA KEV 3 Nov 2021
  • Used in ransomware campaigns

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.

Key facts

Published
5 Oct 2021
Last changed
21 Oct 2025
Assigned by
apache
KEV added
3 Nov 2021
KEV fix due
17 Nov 2021
Used in ransomware
Yes, according to CISA
EPSS
99.992% likely to be exploited in the next 30 days, higher than 99.986% of CVEs (scores for 15 Nov 2026)
SSVC (CISA)
Exploitation: active; Automatable: yes; Technical impact: total

Severity scores

Each score is shown as its source gave it. They are not averaged or merged.

  • 7.5CVSS 3.1, Highfrom CISA (ADP container)CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:H/I:N/A:N

What to do

  • Apply updates per vendor instructions.CISA KEV required action

Historical context and remediation

This reference retains the original CVE publication date. A recent record update does not mean a new attack occurred.

No separately sourced impact summary is available on this page yet. Consult the description, version data and dated exploitation evidence.

Version statuses below come from the CNA. An “unaffected” version is not necessarily a currently supported release or proof of a patch date. EPSS is a dated risk estimate, not a count of historical attacks.

Read the original CVE record.

Affected products

VendorProductVersions
Apache Software FoundationApache HTTP Server
  • Apache HTTP Server 2.4 2.4.49 (affected)

Timeline

  1. 29 Sep 2021 reported
  2. 1 Oct 2021 fixed by r1893775 in 2.4.50
  3. 5 Oct 2021 Published
  4. 3 Nov 2021 CVE-2021-41773 added to CISA KEV
  5. 3 Nov 2021 Added to the CISA KEV catalogue

Weakness

Practice this bug class

HackZoneLabs has a hands-on lab on Path traversal (CWE-22).

Open the learning platform

References