apache http-server CVE-2021-42013 vulnerability in Apache and Other Products
Published on October 7, 2021

Path Traversal and Remote Code Execution in Apache HTTP Server 2.4.49 and 2.4.50 (incomplete fix of CVE-2021-41773)

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It was found that the fix for CVE-2021-41773 in Apache HTTP Server 2.4.50 was insufficient. 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 only affects Apache 2.4.49 and Apache 2.4.50 and not earlier versions.

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Known Exploited Vulnerability

This Apache HTTP Server 2.4.49 and 2.4.50 Path Traversal vulnerability is part of CISA's list of Known Exploited Vulnerabilities. Apache HTTP server vulnerabilities allow an attacker to use a path traversal attack to map URLs to files outside the expected document root and perform Remote Code Execution.

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

Vulnerability Analysis

CVE-2021-42013 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 be critical as this vulnerability has a high impact to the confidentiality, integrity and availability of this component.

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

Timeline

reported

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-2021-42013 has been classified to as a Directory traversal vulnerability or weakness.


Products Associated with CVE-2021-42013

You can be notified by email with stack.watch whenever vulnerabilities like CVE-2021-42013 are published in these products:

Apache HTTP Server
 
Fedora Project Fedora
 
Oracle Instantis Enterprisetrack
 
Oracle Secure Backup
 
NetApp Cloud Backup
 
Oracle Jd Edwards Enterpriseone Tools
 

Affected Versions

Apache Software Foundation Apache HTTP Server:

Exploit Probability

EPSS
94.41%
Percentile
99.98%

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.