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Actively exploited · Published Oct 5, 2021 · Assigned by apache

CVE-2021-41773Path traversal and file disclosure vulnerability in Apache HTTP Server 2.4.49

High 7.5 Exploited Ransomware

In plain English

A high-severity path traversal in Apache HTTP Server from Apache Software Foundation. Attackers are actively exploiting it in the wild (listed by CISA on November 3, 2021). It has been used in ransomware campaigns. The chance it is exploited in the next 30 days is estimated at 100.0% (higher than 99.9% of all known vulnerabilities). Ready-made attack tooling exists: Metasploit, Nuclei, public proof-of-concept code. Fixed versions are available - upgrade the affected package.

Severity (CVSS 3.1)7.5High
Exploit odds (30 days)100.0%top 0.0% of all CVEs
Exploited in the wildYesCISA KEV since Nov 3, 2021
Attack tooling3Metasploit, Nuclei, Public PoC

CISA guidance

Apply updates per vendor instructions.

Federal agencies must remediate by Nov 17, 2021.

Official 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 packages & fixed versions

EcosystemPackageFixed inAdvisory
Alpine:v3.20apache22.4.50-r0ALPINE-CVE-2021-41773
Alpine:v3.21apache22.4.50-r0ALPINE-CVE-2021-41773
Alpine:v3.22apache22.4.50-r0ALPINE-CVE-2021-41773
Alpine:v3.23apache22.4.50-r0ALPINE-CVE-2021-41773
Alpine:v3.24apache22.4.50-r0ALPINE-CVE-2021-41773
Debian:12apache22.4.50-1DEBIAN-CVE-2021-41773
Debian:13apache22.4.50-1DEBIAN-CVE-2021-41773
Debian:14apache22.4.50-1DEBIAN-CVE-2021-41773

Affected products (as reported)

VendorProductVersions
Apache Software Foundation Apache HTTP Server Apache HTTP Server 2.4 2.4.49

Weakness: CWE-22 · Vector: CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:H/I:N/A:N

References