CVE-2021-42013VulnerabilityPublished 11/03/2021Updated 10/24/2026

CVE-2021-42013: Apache HTTP Server Path Traversal Vulnerability

Affects Apache HTTP ServerSource CISA KEV

Severity

High

No CVSS score published yet

Exploitation: Actively exploited – in CISA KEV since 11/03/2021
KEV deadline: 11/17/2021
Ransomware: Used in ransomware campaigns
EPSS: 100.0% chance of exploitation in 30 days – higher than 99% of CVEs

What to do

CISA required action

Apply updates per vendor instructions.

nvd.nist.gov/vuln/detail/CVE-2021-42013 (opens in a new tab)

Description

CVE-2021-42013 is a path traversal vulnerability in Apache HTTP Server that enables remote code execution under certain conditions, such as when files outside Alias-like configured directories are accessible or when CGI scripts are enabled. This vulnerability is a follow-up to an incomplete patch for CVE-2021-41773 and has been exploited in the wild, including in ransomware campaigns.

Summary

Apache HTTP Server contains a path traversal vulnerability (CVE-2021-42013) that allows attackers to perform remote code execution if files outside directories configured by Alias-like directives are not protected by default 'require all denied' settings or if CGI scripts are enabled. This issue resolves an incomplete patch for CVE-2021-41773. The vulnerability has been exploited in the wild and is known to be used in ransomware campaigns.

Impact

Successful exploitation of this vulnerability can lead to remote code execution on affected Apache HTTP Server instances. This can allow attackers to execute arbitrary code with the privileges of the web server, potentially leading to full system compromise. The vulnerability has been actively exploited in the wild and used in ransomware campaigns, indicating a high risk to affected systems.

Mitigation

Patch status is not yet confirmed — check the vendor advisory for current remediation guidance. Until an official fix is confirmed, administrators should ensure that directories outside Alias-like configured paths are protected with 'require all denied' directives and disable CGI scripts if not needed to reduce exposure.

Weaknesses

CWE-22Path Traversal (opens in a new tab)

What to do

Description

AnalysisAI-generated, updated 10/24/2026, 09:42:00 UTC

Weaknesses

References

Related threats