CVE-2021-41773
Apache HTTP Server Path Traversal Vulnerability
IN CISA KEV
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
- Apache
- Product
- HTTP Server
- CVSS 3.1
- 9.8 (critical), scored by NVD (primary)CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:H/I:H/A:H
- CVSS 3.1
- 7.5 (high), scored by 134c704f-9b21-4f2e-91b3-4a467353bcc0CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:H/I:N/A:N
- CWE
- CWE-22
- Published
- 2021-10-05
- NVD modified
- 2026-06-17
- NVD status
- Analyzed
CISA KEV
- Date added
- 2021-11-03
- Due date
- 2021-11-17
- Ransomware use
- Known
- Required action
- Apply updates per vendor instructions.
EPSS
100% chance of exploitation in the next 30 days (percentile 99th)
FIRST EPSS, updated 17 Oct 2026. About EPSS
CVSS is severity, EPSS is likelihood, KEV means already exploited. EPSS is a statistical probability, not a certainty: a low score does not make a bug safe, and a high one does not prove it is being exploited.
References
- www.openwall.com (Mailing List, Third Party Advisory)
- www.openwall.com (Mailing List, Third Party Advisory)
- www.openwall.com (Mailing List, Third Party Advisory)
- www.openwall.com (Mailing List, Third Party Advisory)
- www.openwall.com (Mailing List, Third Party Advisory)
- www.openwall.com (Mailing List, Third Party Advisory)
- www.openwall.com (Mailing List, Third Party Advisory)
- www.openwall.com (Mailing List, Third Party Advisory)
- www.openwall.com (Mailing List, Patch, Third Party Advisory)
- www.openwall.com (Mailing List, Patch, Third Party Advisory)
- www.openwall.com (Mailing List, Third Party Advisory)
- httpd.apache.org (Release Notes, Vendor Advisory)
Data last updated 18 Oct 2026. Sources: NVD API 2.0, CISA KEV catalog, FIRST EPSS. Links: NVD, CISA KEV. Metadata only. ThreatWire does not host exploit code.