CVE-2021-41773VulnerabilityPublished 11/03/2021Updated 10/24/2026

CVE-2021-41773: 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-2021-41773 (opens in a new tab)

Description

CVE-2021-41773 is a path traversal vulnerability in Apache HTTP Server that can enable remote code execution if certain directory configurations or CGI scripts are present. The initial patch for this vulnerability was insufficient, and further remediation is detailed under CVE-2021-42013. This vulnerability has been exploited in the wild and is associated with known ransomware campaigns.

Summary

Apache HTTP Server contains a path traversal vulnerability (CWE-22) that allows attackers to access files outside of intended directories if those directories are not protected by default 'require all denied' settings or if CGI scripts are enabled. Successful exploitation can lead to remote code execution. The original patch issued for CVE-2021-41773 was found to be insufficient, prompting additional remediation guidance under CVE-2021-42013. This vulnerability has been actively exploited in the wild and linked to ransomware activity.

Impact

Exploitation of this vulnerability can lead to unauthorized access to files outside of configured directories and potentially remote code execution on affected Apache HTTP Server instances. This poses a significant risk of system compromise and has been observed in active ransomware campaigns.

Mitigation

The initial patch for CVE-2021-41773 is insufficient; users should refer to the remediation information provided under CVE-2021-42013 for complete mitigation. Ensure that directories outside Alias-like directives are protected by 'require all denied' and disable CGI scripts if not needed. Monitor the vendor advisory for official fixes and updates.

Weaknesses

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

What to do

Description

AnalysisAI-generated, updated 10/24/2026, 09:41:58 UTC

Weaknesses

References

Related threats