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.
Published 2021-10-05 09:15:08
Updated 2022-10-28 16:16:22
View at NVD,   CVE.org
Vulnerability category: Directory traversalExecute code

Threat overview for CVE-2021-41773

Top countries where our scanners detected CVE-2021-41773
Top open port discovered on systems with this issue 80
IPs affected by CVE-2021-41773 5,494
Threat actors abusing to this issue? Yes
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CVE-2021-41773 is in the CISA Known Exploited Vulnerabilities Catalog

This issue is known to have been leveraged as part of a ransomware campaign.
CISA vulnerability name:
Apache HTTP Server Path Traversal Vulnerability
CISA required action:
Apply updates per vendor instructions.
CISA description:
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. The original patch issued under this CVE ID i
Added on 2021-11-03 Action due date 2021-11-17

Exploit prediction scoring system (EPSS) score for CVE-2021-41773

Probability of exploitation activity in the next 30 days: 97.44%

Percentile, the proportion of vulnerabilities that are scored at or less: ~ 100 % EPSS Score History EPSS FAQ

Metasploit modules for CVE-2021-41773

  • Apache 2.4.49/2.4.50 Traversal RCE scanner
    Disclosure Date: 2021-05-10
    First seen: 2022-12-23
    auxiliary/scanner/http/apache_normalize_path
  • Apache 2.4.49/2.4.50 Traversal RCE
    Disclosure Date: 2021-05-10
    First seen: 2022-12-23
    exploit/multi/http/apache_normalize_path_rce

CVSS scores for CVE-2021-41773

Base Score Base Severity CVSS Vector Exploitability Score Impact Score Score Source
4.3
MEDIUM AV:N/AC:M/Au:N/C:P/I:N/A:N
8.6
2.9
nvd@nist.gov
7.5
HIGH CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:H/I:N/A:N
3.9
3.6
nvd@nist.gov

CWE ids for CVE-2021-41773

  • The product uses external input to construct a pathname that is intended to identify a file or directory that is located underneath a restricted parent directory, but the product does not properly neutralize special elements within the pathname that can cause the pathname to resolve to a location that is outside of the restricted directory.
    Assigned by:
    • nvd@nist.gov (Primary)
    • security@apache.org (Secondary)

References for CVE-2021-41773

Products affected by CVE-2021-41773

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