CVE-2021-41773

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…

Browse: All 2021 CVEs · All vendors

CVSS score
9.8 Critical
CVSS vector
CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:H/I:H/A:H
CISA KEV
Yes — actively exploited (added 2021-11-03, remediation due 2021-11-17)
Ransomware
Known ransomware campaign use
Weakness (CWE)
CWE-22
Published
2021-10-05
Last modified
2026-06-17
NVD status
Analyzed

Description

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.

Affected products

Affected ranges per NVD CPE data; confirm exact versions in the vendor advisory.

Required action (CISA)

Apply updates per vendor instructions. Federal remediation deadline: 2021-11-17.

How to prioritize this

This vulnerability is on the CISA KEV list, meaning it is being actively exploited — treat it as urgent regardless of the raw CVSS number. Use the live CVE lookup for the latest NVD data, and the CVSS 3.1 calculator to model your own environmental score. For the actively exploited vulnerabilities that matter this week, read The Exploit HQ daily security brief.

References

FAQ

Is CVE-2021-41773 actively exploited?

Yes. CISA added CVE-2021-41773 to its Known Exploited Vulnerabilities (KEV) catalog on 2021-11-03, with a federal remediation deadline of 2021-11-17. A KEV listing means real-world exploitation is confirmed, so patching this should be prioritized above many higher-CVSS bugs that aren't being exploited.

What is the CVSS score of CVE-2021-41773?

CVE-2021-41773 has a CVSS base score of 9.8 (Critical). Its vector string is CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:H/I:H/A:H.

Related vulnerabilities

Data source: NVD & CISA KEV. Shown as-is; nothing added. Last generated from NVD data — re-check the live tool for updates.