CISA KEV · Known exploitedCritical

CVE-2021-42013

Apache HTTP Server

It was found that the fix for CVE-2021-41773 in Apache HTTP Server 2.4.50 was insufficient. 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 only affects Apache 2.4.49 and Apache 2.4.50 and not earlier versions.

CVSS: 9.8
EPSS: 100.0%
CISA KEV: Listed
Published: 2021.10.08

PRIORITY ASSESSMENT

Immediate review

CISA has listed this vulnerability in the Known Exploited Vulnerabilities catalog.

Known exploitationConfirmed by CISA KEV

Exploit probability100.0%

Technical severityCVSS 9.8

Vulnerability overview

Affected product and versions

Product: Apache HTTP Server
Affected versions: Apache HTTP Server 2.4.49, Apache HTTP Server 2.4.50, 2.4.49, 2.4.50, 34, 35, 17.1, 17.2, 17.3, < 9.2.6.0, < 18.1.0.1.0
Fixed versions: 9.2.6.0, 18.1.0.1.0

Recommended response sequence

Confirm exposure before applying a vendor-supported change.

Full remediation guide

CISA required action

Apply updates per vendor instructions.

Due date: 2021.11.17

1
Identify
Confirm that Apache HTTP Server and an affected version are present.
2
Prioritize
Combine exploitation signals with asset exposure and business criticality.
3
Remediate
Follow the vendor advisory or supported update path and preserve rollback options.
4
Verify
Recheck the version, service health, access paths, and relevant logs.

Technical data

CVSS vector: CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:H/I:H/A:H
CWE: CWE-22
KEV added: 2021.11.03
Ransomware use: 확인됨