CVE intelligence and bounded remediation

CVE-2021-41773 — Apache HTTP Server Path Traversal Vulnerability

Critical CVSS 9.8 CISA KEV

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.

Severity
Critical
CVSS
9.8 (3.1)
Published
2021-10-05
CISA KEV
Known exploited
Ecosystem
software/application
Weaknesses
CWE-22

Affected products

  • apache / http_server / 2.4.49
  • fedoraproject / fedora / 34
  • fedoraproject / fedora / 35
  • oracle / instantis_enterprisetrack / 17.1
  • oracle / instantis_enterprisetrack / 17.2
  • oracle / instantis_enterprisetrack / 17.3

Showing 6 representative product identities from 7 source matches. Confirm exact affected versions with the linked vendor and NVD evidence.

Matched remediation archetype

Path traversal, unsafe upload, and file handling

This catalog composition supplies bounded fallback guidance. Explicitly reviewed curated workflows load with the complete record below.

Check exposure

  • Trace untrusted filenames, archive entries, URLs, and path segments into read, write, include, extraction, and upload operations.
  • Identify filesystem roots, mount permissions, symbolic-link behavior, archive handling, and whether uploaded content is web-accessible or executable.
  • Review canonicalization and containment checks across supported operating systems and storage backends.

Remediate safely

  • Generate server-side storage identifiers and resolve paths beneath a fixed root using filesystem-aware containment checks.
  • Reject absolute, parent-relative, alternate-separator, device, link, and archive entries that escape the intended root.
  • Store uploads outside executable or served paths, validate type and size, and use private atomic temporary files.

Authoritative sources

Complete CVE record and remediation plan

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