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CVE

CVE-2021-41773

Apache HTTP Server Path Traversal Vulnerability

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.

CRITICAL · CVSS 9.8 ⚠ CISA KEV EPSS 0.94391 Ransomware: known
Act now
  • Listed on CISA KEV (known exploited in the wild)
  • Linked to known ransomware campaigns
  • SSVC exploitation status: active
  • EPSS ≥ 0.50 - high probability of exploitation in the next 30 days
  • EPSS percentile: top 0% of all CVEs by exploitation likelihood
  • Public exploit or PoC is available
  • SSVC automatable: yes - attacks can be scripted at scale
  • CVSS base score ≥ 7.0
Sigma rules0 YARA rules0

Required Remediation

Apply updates per vendor instructions.

Affected Products & Versions

4

Detection Rules (IDS/IPS)

4

Scoring & Timeline

9.8
CRITICAL · CVSS v3.1 · security@apache.org
View on NVD
Attack Vector
Network Adjacent Local Physical
Attack Complexity
Low High
Privileges Required
None Low High
User Interaction
None Required
Scope
Unchanged Changed
Confidentiality
None Low High
Integrity
None Low High
Availability
None Low High
Published to NVD05 Oct 2021 · 09:15 AM
CVSS VectorCVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:H/I:H/A:H
SSVC triage · cisa-vulnrichment
Exploitation
active
Automatable
yes
Technical impact
total
SSVC asks the questions that actually drive patch urgency: is it being exploited, can attacks be automated, and how total is the impact.

Vendor Advisories

5
suse-csafopenSUSE-SU-2024:11560-1
cisco-csafcisco-sa-apache-httpd-pathtrv-LAzg68cZ
🔗

References & Sources

26
Source URLs (vendor pages, mailing lists, write-ups). Exploit/PoC links are in their own section above to avoid duplication.
http://www.openwall.com/lists/oss-security/2021/10/08/1ExploitMailing ListThird Party Advisory
http://www.openwall.com/lists/oss-security/2021/10/08/3ExploitMailing ListThird Party Advisory
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