CVE Analysis 3 min read

CVE-2026-41448: AdGuard Home, when started Directory traversal

CVE-2026-41448 CVSS 9.4 CRITICAL vulnerability analysis

CVE-2026-41448 is a critical severity vulnerability (CVSS 9.4) identified in the National Vulnerability Database. AdGuard Home, when started with the --glinet flag, contains an authentication bypass vulnerability that allows unauthenticated attackers to gain full admin access by supplying a path traversal sequence in the Admin-Token cookie, exploiting unsanitized string concatenation in the token file path construction within the authglinet middleware.

TL;DR: This is a directory traversal vulnerability (CVSS 9.4 CRITICAL). Authentication: Not required (unauthenticated). Patch immediately.

What This Vulnerability Is

AdGuard Home, when started with the --glinet flag, contains an authentication bypass vulnerability that allows unauthenticated attackers to gain full admin access by supplying a path traversal sequence in the Admin-Token cookie, exploiting unsanitized string concatenation in the token file path construction within the authglinet middleware. Attackers can craft a request with a traversal payload in the Admin-Token header to redirect file reads to arbitrary paths.

The National Vulnerability Database assigned this issue a CVSS base score of 9.4, placing it in the CRITICAL category. The identifier CVE-2026-41448 was published on 2026-06-08T17:16:42.847.

CVE Identifier
CVE-2026-41448
CVSS Base Score
9.4 / 10.0 (CRITICAL)
Published
2026-06-08T17:16:42.847
NVD Entry
https://nvd.nist.gov/vuln/detail/CVE-2026-41448
MITRE Entry
https://cve.mitre.org/cgi-bin/cvename.cgi?name=CVE-2026-41448

Who Is Affected

Based on the vulnerability data published by NVD, the following products and configurations are identified as affected:

  • Specific affected products are listed in the NVD entry. Review the CPE data for your stack.

If your organization uses any of the above, this vulnerability applies to your environment. Even if your specific version is not listed, review the full CPE match data to confirm.

What Attack Traffic Looks Like

Illustrative patterns for defensive detection. Not a working exploit.

Path traversal attempts use dot-dot-slash sequences to access files outside intended directories:

../../etc/passwd
..%2f..%2fetc%2fpasswd
....//....//etc/passwd
%2e%2e%2f%2e%2e%2f
..%252f..%252f (double encoding)

How to Detect It

Sigma Rule

title: Path Traversal in HTTP Request
id: auto-cwe22-detection
status: experimental
description: Detects directory traversal sequences in HTTP requests.
logsource:
  category: webserver
detection:
  selection:
    cs-uri-stem|re: '(\.\./|\.\.\\|%2e%2e%2f|%2e%2e/|\.%2e/|%252e%252e)'
  condition: selection
level: high

Detection Regex

(?i)(\.\./|\.\.\\|%2e%2e(%2f|/|\\)|%252e%252e)

IOC Hunt List

  • Access to sensitive system files (/etc/passwd, /etc/shadow, web.config) in access logs
  • HTTP responses containing system file content
  • Requests with unusually deep relative paths

What to Do About It

Here is what we recommend, in order of priority:

  1. Check your exposure. Determine whether the affected software or component is present in your environment. Asset inventories and software composition analysis (SCA) tools are the fastest route.
  2. Apply the patch. If a vendor patch or updated version is available, apply it. Check the references below for vendor advisories.
  3. Mitigate if patching is not immediate. If you cannot patch right now, evaluate whether network segmentation, access control changes or configuration adjustments reduce the attack surface for this specific vulnerability.
  4. Monitor for exploitation. Check whether proof-of-concept exploit code exists. The CISA Known Exploited Vulnerabilities catalog tracks actively exploited CVEs.
  5. Document your response. Record what you checked, when you patched and what residual risk remains. This matters for compliance and for incident response if this vulnerability is exploited later.

Triage Quick Start

Run as administrator. Collect artifacts before applying patches or making changes:

# Linux/Unix systems
tar czf /tmp/triage-$(hostname)-$(date +%s).tgz \
  /var/log/syslog /var/log/auth.log /var/log/messages \
  /var/log/secure /var/log/apache2/ /var/log/nginx/ \
  /etc/passwd /etc/shadow \
  /root/.bash_history \
  /home/*/.bash_history \
  /tmp/ /var/tmp/ 2>/dev/null

# Windows systems (PowerShell)
# Compress-Archive -Path C:\Windows\System32\winevt\Logs\*,C:\inetpub\logs\* -DestinationPath C:\triage.zip

If you need help analyzing these artifacts, call Sherlock Forensics at 604.229.1994.

Why This Matters for Companies Without Security Teams

A CVSS score of 9.4 means this vulnerability is straightforward to exploit, likely to cause significant damage or both. For startups and small companies operating without a dedicated security team, vulnerabilities at this severity level represent real operational risk rather than theoretical concern.

The challenge is not awareness. Vulnerability databases are public. The challenge is triage: understanding whether a given CVE affects your specific stack and knowing what to do about it before an attacker does. If you lack the internal capacity to perform that assessment, an external review of your exposure is a concrete next step.

Sherlock Forensics provides vulnerability assessment and penetration testing for organizations that need to understand their attack surface without building a full internal security function.

References and Further Reading