CVE-2026-79768 Overview
CVE-2026-79768 is a path equivalence vulnerability in the Apache HTTP Server mod_userdir module. The flaw affects configurations using the absolute non-wildcard form of the UserDir directive. Attackers can leverage a single-dot directory (/./) in request paths to bypass intended access restrictions and disclose information. The issue is classified under CWE-55: Path Equivalence 'filename/./' (Trailing Dot).
The vulnerability affects Apache HTTP Server versions 2.4.0 through 2.4.68. Remote attackers can exploit it without authentication or user interaction over the network.
Critical Impact
Remote unauthenticated attackers can craft URLs containing /./ to bypass path restrictions in mod_userdir, leading to unintended information disclosure from user directories.
Affected Products
- Apache HTTP Server 2.4.0 through 2.4.68
- Deployments using mod_userdir with absolute non-wildcard UserDir directive
- Shared hosting environments relying on mod_userdir for per-user content
Discovery Timeline
- 2026-10-01 - CVE-2026-79768 published to NVD
- 2026-10-05 - Last updated in NVD database
Technical Details for CVE-2026-79768
Vulnerability Analysis
The mod_userdir module maps request URIs beginning with /~username to filesystem paths. When administrators configure the second form of the UserDir directive, which uses an absolute path without a wildcard, the module constructs filesystem paths from the request URI. The vulnerability occurs because the module does not treat path segments containing /./ as equivalent to the base path during access control evaluation.
This path equivalence issue allows attackers to craft URIs that resolve to the same filesystem resource through alternate representations. The server may serve content that administrators intended to restrict. Confidentiality is impacted while integrity and availability remain unaffected.
Root Cause
The root cause is improper normalization of path segments in mod_userdir before access decisions are made. The CWE-55 classification identifies the specific class of weakness: Apache treats /path and /./path as distinct for access checks but equivalent for file resolution. This mismatch between normalization during authorization and normalization during file resolution creates the bypass condition.
Attack Vector
Attackers send HTTP requests to vulnerable Apache instances with URIs that embed /./ sequences within mod_userdir-mapped paths. The attack requires no credentials, no user interaction, and only basic HTTP request-crafting capability. Exploitation is network-reachable against any public-facing Apache server running an affected version with the vulnerable UserDir configuration.
The vulnerability is described in prose because no verified public exploit code is available. Refer to the Apache HTTP Server security bulletin and the Openwall OSS-Security disclosure for additional technical context.
Detection Methods for CVE-2026-79768
Indicators of Compromise
- HTTP access log entries containing /./ sequences in requests targeting /~username/ paths handled by mod_userdir
- Unexpected 200-status responses for user directory URIs that should return 403 or 404
- Repeated probing of mod_userdir-mapped paths from a single source address with path-normalization variants
Detection Strategies
- Audit all Apache configuration files for UserDir directives using the absolute non-wildcard form
- Review access logs for request URIs matching the pattern /~[^/]+/\./ and correlate with response status codes
- Deploy a web application firewall rule that flags or blocks URIs containing /./ segments against mod_userdir endpoints
Monitoring Recommendations
- Forward Apache access and error logs to a centralized analytics platform for pattern analysis across the fleet
- Alert on anomalous spikes in requests targeting /~ paths, particularly from unfamiliar source networks
- Track Apache HTTP Server version inventory and alert when hosts remain on versions 2.4.0 through 2.4.68
How to Mitigate CVE-2026-79768
Immediate Actions Required
- Upgrade Apache HTTP Server to a version later than 2.4.68 that includes the fix for CVE-2026-79768
- Inventory all Apache instances and identify configurations using the vulnerable UserDir absolute non-wildcard form
- Restrict external exposure of mod_userdir-enabled servers until patches are applied
Patch Information
The Apache Software Foundation addresses the vulnerability in versions released after 2.4.68. Consult the Apache HTTP Server 2.4 vulnerabilities page for the exact fixed version and advisory details before deploying updates.
Workarounds
- Disable mod_userdir entirely if per-user web directories are not required in the environment
- Switch to the wildcard form of the UserDir directive, which is not affected by this vulnerability
- Add a reverse proxy or WAF rule in front of Apache that normalizes or rejects request URIs containing /./ segments
- Apply explicit <Directory> and <Location> access controls that account for alternate path representations
Disclaimer: This content was generated using AI. While we strive for accuracy, please verify critical information with official sources.