CVE-2021-42013
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. This CVE ID resolves an incomplete patch for CVE-2021-41773.
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:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:H/I:H/A:H- jvn.jp/en/jp/JVN51106450/index.htmlThird Party Advisory
- packetstormsecurity.com/files/164501/Apache-HTTP-Server-2.4.50-Path-Traversal-Code-Execution.htmlExploitThird Party Advisory
- packetstormsecurity.com/files/164609/Apache-HTTP-Server-2.4.50-Remote-Code-Execution.htmlExploitThird Party Advisory
- packetstormsecurity.com/files/164629/Apache-2.4.49-2.4.50-Traversal-Remote-Code-Execution.htmlExploitThird Party Advisory
- packetstormsecurity.com/files/164941/Apache-HTTP-Server-2.4.50-Remote-Code-Execution.htmlExploitThird Party Advisory
- packetstormsecurity.com/files/165089/Apache-HTTP-Server-2.4.50-CVE-2021-42013-Exploitation.htmlThird Party AdvisoryVDB Entry
- packetstormsecurity.com/files/167397/Apache-2.4.50-Remote-Code-Execution.htmlExploitThird Party Advisory
- openwall.com/lists/oss-security/2021/10/07/6Mailing ListThird Party Advisory
- openwall.com/lists/oss-security/2021/10/08/1Mailing ListThird Party Advisory
- openwall.com/lists/oss-security/2021/10/08/2Mailing ListThird Party Advisory
- openwall.com/lists/oss-security/2021/10/08/3Mailing ListThird Party Advisory
- openwall.com/lists/oss-security/2021/10/08/4Mailing ListThird Party Advisory
Actively exploited and used by ransomware crews. Patch immediately.
- Exploitation
- Confirmed in the wild (CISA KEV)
- Federal remediation deadline
- Overdue by 1805 days
- Ransomware
- Used in known ransomware campaigns
- CVSS
- 9.8 CRITICAL
- EPSS (30-day exploit probability)
- 100.0% · top 1% of all CVEs
- Weakness
- CWE-22
- Attack vector
- Network, remotely reachable
- Preconditions
- No privileges and no user interaction
- 1.Apply updates per vendor instructions.
- 2.Treat as emergency change: patch or isolate internet-facing instances first.
- 3.Review exposure: confirm which instances are reachable from the internet and restrict access until patched.
- 4.Hunt for compromise: review logs for the disclosure window, not just from the patch date.
- 5.Verify offline/immutable backups and segment the affected systems. This flaw is used for ransomware initial access.
Assessment is derived automatically from the live signals above; verify against your own asset inventory.