Exploited vulnerability · CISA KEV

Is CVE-2021-42013 exploited? Yes: in CISA KEV since 3 Nov 2021

Gociux · Apache HTTP Server · data: CISA KEV, CVE record, FIRST EPSS

Yes. CVE-2021-42013, Apache HTTP Server Path Traversal Vulnerability, is being exploited in the wild. CISA added it to its Known Exploited Vulnerabilities catalog on 3 Nov 2021, 27 days after it was published. It is known to be used in ransomware campaigns. It affects Apache HTTP Server. If you run it, CISA's required action is: Apply updates per vendor instructions.

What it is

Apache HTTP Server contains a path traversal vulnerability that allows an attacker to perform remote code execution if files outside directories configured by Alias-like directives are not under default require all denied or if CGI scripts are enabled. This CVE ID resolves an incomplete patch for CVE-2021-41773.

What to do

1. Check whether you run it. Look for HTTP Server in your asset inventory, including appliances and cloud images. Stack check lists every exploited Apache CVE at once.
2. Apply the fix. Apply updates per vendor instructions.
3. If you can't patch today, take the affected service off the internet or restrict who can reach it, and check its logs for signs of compromise since 7 Oct 2021.
4. Get told next time. Email alerts when CISA adds a CVE for Apache.

Other exploited CVEs in HTTP Server

• CVE-2024-38475: Apache HTTP Server Improper Escaping of Output Vulnerability (1 May 2025)
• CVE-2021-41773: Apache HTTP Server Path Traversal Vulnerability (3 Nov 2021)
• CVE-2019-0211: Apache HTTP Server Privilege Escalation Vulnerability (3 Nov 2021)

References

• nvd.nist.gov/vuln/detail/CVE-2021-42013

Sources: CISA KEV (exploitation, ransomware use, required action, due date), the CVE record (publication date, CVSS, CNA), NVD and FIRST EPSS (live score). More: all KEV additions in November 2021 · Apache scorecard · act-now radar.