Path Traversal in Apache HTTP Server
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 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.
Vulnerability class: Path Traversal (Directory Traversal)
EPSS: 1.000 (100.0th percentile) — read the EPSS interpretation.
CVSS v3 metric
CVSS v3 base score 9.8 (Critical). Vector: CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:H/I:H/A:H.
Affected products
- Apache Http_server — versions 2.4.49
- Apache Software Foundation Http Server — versions Apache HTTP Server 2.4 2.4.49
- Netapp Cloud_backup
- Oracle Instantis_enterprisetrack — versions 17.1, 17.2, 17.3
- Fedoraproject Fedora — versions 34, 35
Weakness classification (CWE)
CISA KEV (Known Exploited Vulnerabilities)
This CVE is on the CISA KEV catalog, added on . CISA KEV inclusion means CISA has confirmed in-the-wild exploitation; US federal agencies are required to remediate within a published due date.
BOD 22-01 due date: .
Required action: Apply updates per vendor instructions.
Known ransomware campaign use: yes.
Public proof-of-concept exploits
References
- security@apache.org (x_refsource_MISC, Release Notes, Vendor Advisory)
- security@apache.org (mailing-list, x_refsource_MLIST, Mailing List)
- security@apache.org (mailing-list, x_refsource_MLIST, Mailing List)
- security@apache.org (mailing-list, x_refsource_MLIST, Mailing List, Third Party Advisory)
- security@apache.org (mailing-list, x_refsource_MLIST, Mailing List, Third Party Advisory)
- security@apache.org (mailing-list, x_refsource_MLIST, Mailing List)
- security@apache.org (mailing-list, x_refsource_MLIST, Mailing List)
- security@apache.org (mailing-list, x_refsource_MLIST, Mailing List, Third Party Advisory)
- security@apache.org (x_refsource_CISCO, vendor-advisory, Third Party Advisory)
- security@apache.org (mailing-list, x_refsource_MLIST, Exploit, Mailing List, Third Party Advisory)
Frequently asked questions
- What is CVE-2021-41773?
- CVE-2021-41773 is a critical-severity vulnerability in Apache HTTP Server, classified under Path Traversal. CVSS score: 9.8/10. Published 2021-10-05.
- How severe is CVE-2021-41773?
- Critical severity. CVSS v3 base score is 9.8 out of 10.
- Is CVE-2021-41773 known to be exploited?
- Yes. CVE-2021-41773 is listed in the CISA Known Exploited Vulnerabilities catalog (added 2021-11-03), indicating it is being actively exploited. 629 public proof-of-concept repositories are indexed.