Path Traversal and Remote Code Execution in Apache HTTP Server 2.4.49 and 2.4.50 (incomplete fix of CVE-2021-41773)
Only affects Apache HTTP Server 2.4.49 and 2.4.50 with CGI scripts enabled on aliased paths. Fixed in 2.4.51.
- Published
- Last modified
- Where the record stands: published, rejected by its publisher, or superseded by another id.What do these mean? →
- published
- Whether CISA lists it in its Known Exploited Vulnerabilities catalog: proof that attackers are using it.What do these mean? →
- Listed in CISA KEV
- How many real-world setups can hit the bug, from the vendor's advisory and CISA data. It does not know your setup.What do these mean? →
- Actively exploited
- Fix
- Fixed in 2.4.51
- Whether working attack code is public (Exploit-DB, Metasploit, Nuclei or GitHub). Public code makes attacks easier.What do these mean? →
- None on Exploit-DB, Metasploit or GitHub
Summary
Apache HTTP Server, a widely used open-source web server, is affected by this vulnerability. An attacker could use crafted URLs to read files outside the intended web directories and, if CGI scripts are enabled for those paths, run arbitrary code on the server.
Summarized by anthropic/claude-haiku-5.5. Verify details against the original sources.
Read the original description
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.
Timeline
- CVE published
- Added to CISA KEV
CISA has evidence of exploitation in the wild
- CISA remediation deadline
Due date for US federal agencies to patch
- Record last updated
- EPSS reached 10%
FIRST estimates at least a 10% chance of exploitation in the next 30 days
Affected versions
- Apache Software Foundation Apache HTTP Server
Apache HTTP Server 2.4.49, Apache HTTP Server 2.4.50
References 25
httpd.apache.org
lists.apache.org
openwall.com
- lists/oss-security/2021/10/07/6
- lists/oss-security/2021/10/08/1
- lists/oss-security/2021/10/08/2
- lists/oss-security/2021/10/08/3
- lists/oss-security/2021/10/08/4
- lists/oss-security/2021/10/08/6
- lists/oss-security/2021/10/08/5
- lists/oss-security/2021/10/09/1
- lists/oss-security/2021/10/11/4
- lists/oss-security/2021/10/15/3
- lists/oss-security/2021/10/16/1
lists.fedoraproject.org
oracle.com
security.netapp.com
Questions about CVE-2021-42013
What does this mean?
A path traversal flaw lets URLs map to files outside the Alias-like directories. Where CGI scripts are enabled for those aliased paths, this can allow remote code execution.Source: sec.cloudapps.cisco.com, lists.fedoraproject.org
Am I affected, and how do I check?
Versions 2.4.49 and 2.4.50 are affected. Files outside the aliased directories are not protected by the usual default 'require all denied' setting, and remote code execution also needs CGI scripts enabled for the aliased paths. To check, look at the version reported by httpd -v and whether CGI is enabled for Alias paths in the configuration.Source: sec.cloudapps.cisco.com, lists.fedoraproject.org
What should I do about it?
Upgrade to Apache HTTP Server 2.4.51, the fixed version.Source: sec.cloudapps.cisco.com, lists.fedoraproject.org
Is it being exploited?
Yes. CISA added it to its Known Exploited Vulnerabilities catalog on 2021-11-03, which means it has evidence of attacks. No public exploit code is tracked.Source: cisa.gov, cve.now feed data