CVE-2021-41773
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. The original patch issued under this CVE ID is insufficient, please review remediation information under CVE-2021-42013.
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.
CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:H/I:H/A:H- packetstormsecurity.com/files/164418/Apache-HTTP-Server-2.4.49-Path-Traversal-Remote-Code-Execution.htmlExploitThird Party Advisory
- packetstormsecurity.com/files/164418/Apache-HTTP-Server-2.4.49-Path-Traversal.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
- openwall.com/lists/oss-security/2021/10/05/2Mailing ListThird Party Advisory
- openwall.com/lists/oss-security/2021/10/07/1Mailing ListThird Party Advisory
- openwall.com/lists/oss-security/2021/10/07/6Mailing ListThird Party Advisory
- openwall.com/lists/oss-security/2021/10/08/1ExploitMailing List
- openwall.com/lists/oss-security/2021/10/08/2Mailing ListThird Party Advisory
- openwall.com/lists/oss-security/2021/10/08/3ExploitMailing List
- openwall.com/lists/oss-security/2021/10/08/4Mailing ListThird Party Advisory
- openwall.com/lists/oss-security/2021/10/08/5Mailing ListThird Party Advisory
Actively exploited and used by ransomware crews. Patch immediately.
- Exploitation
- Confirmed in the wild (CISA KEV)
- Federal remediation deadline
- Overdue by 1804 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.