apache http-server CVE-2021-41773 vulnerability in Apache and Other Products
Published on October 5, 2021

Path traversal and file disclosure vulnerability in Apache HTTP Server 2.4.49

product logo product logo product logo product logo
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.

Vendor Advisory Vendor Advisory Vendor Advisory Vendor Advisory NVD

Known Exploited Vulnerability

This Apache HTTP Server Path Traversal Vulnerability is part of CISA's list of Known Exploited Vulnerabilities. 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 .

The following remediation steps are recommended / required by November 17, 2021: Apply updates per vendor instructions.

Vulnerability Analysis

CVE-2021-41773 can be exploited with network access, and does not require authorization privileges or user interaction. This vulnerability is considered to have a low attack complexity. This vulnerability is known to be actively exploited by threat actors in an automatable fashion. The potential impact of an exploit of this vulnerability is considered to have a high impact on confidentiality, with no impact on integrity and availability.

Attack Vector:
NETWORK
Attack Complexity:
LOW
Privileges Required:
NONE
User Interaction:
NONE
Scope:
UNCHANGED
Confidentiality Impact:
HIGH
Integrity Impact:
NONE
Availability Impact:
NONE

Timeline

reported

fixed by r1893775 in 2.4.50 2 days later.

Weakness Type

What is a Directory traversal Vulnerability?

The software uses external input to construct a pathname that is intended to identify a file or directory that is located underneath a restricted parent directory, but the software does not properly neutralize special elements within the pathname that can cause the pathname to resolve to a location that is outside of the restricted directory.

CVE-2021-41773 has been classified to as a Directory traversal vulnerability or weakness.


Products Associated with CVE-2021-41773

You can be notified by email with stack.watch whenever vulnerabilities like CVE-2021-41773 are published in these products:

 
 
 
 

Affected Versions

Apache Software Foundation Apache HTTP Server Version Apache HTTP Server 2.4 2.4.49 is affected by CVE-2021-41773

Exploit Probability

EPSS
94.39%
Percentile
99.97%

EPSS (Exploit Prediction Scoring System) scores estimate the probability that a vulnerability will be exploited in the wild within the next 30 days. The percentile shows you how this score compares to all other vulnerabilities.