CVE-2026-53519: Nezha Monitoring Path Traversal Flaw

CVE-2026-53519 Overview

CVE-2026-53519 is a path traversal vulnerability [CWE-22] in Nezha Monitoring, a self-hostable server and website monitoring tool. The flaw resides in the fallbackToFrontend function within the dashboard's NoRoute handler. The handler uses strings.HasPrefix to validate requests targeting /dashboard instead of performing a path-segment match. Attackers can exploit this logic to read arbitrary files on the host without authentication. The maintainers patched the issue in version 2.0.13.

Critical Impact
Unauthenticated remote attackers can read sensitive files such as data/config.yaml from the server filesystem by sending crafted HTTP requests.

Affected Products

Nezha Monitoring versions prior to 2.0.13
Self-hosted Nezha dashboard deployments
Servers exposing the Nezha admin interface to untrusted networks

Discovery Timeline

2026-06-12 - CVE-2026-53519 published to NVD
2026-06-17 - Last updated in NVD database

Technical Details for CVE-2026-53519

Vulnerability Analysis

The vulnerability stems from improper input validation in the dashboard's catch-all route handler. The fallbackToFrontend function treats any URL whose raw string starts with /dashboard as a request for admin-frontend static assets. Because the prefix check uses strings.HasPrefix rather than a path-segment comparison, traversal sequences embedded immediately after the prefix bypass the intended restriction. The handler then serves files outside the admin asset directory.

The Common Weakness Enumeration classifies this issue as CWE-22 (Improper Limitation of a Pathname to a Restricted Directory). No authentication is required, and the attack is performed over the network with low complexity.

Root Cause

The root cause is the substring-based prefix check on untrusted URL input. The handler accepts an input such as /dashboard../data/config.yaml because the string still begins with /dashboard. Subsequent processing with strings.TrimPrefix removes only the literal prefix, leaving ../data/config.yaml. The call path.Join("admin-dist", "../data/config.yaml") then normalizes to data/config.yaml. Finally, os.Stat locates the file and http.ServeFile returns its contents to the requester.

Attack Vector

An unauthenticated attacker sends an HTTP GET request to the dashboard endpoint with a crafted path containing traversal characters appended directly to the /dashboard prefix. The server returns the contents of the targeted file, including configuration files holding database credentials, API tokens, and notification secrets. Exploitation requires only network access to the dashboard port and no user interaction. See the GitHub Security Advisory GHSA-5c25-7vpj-9mqh for additional technical details.

Detection Methods for CVE-2026-53519

Indicators of Compromise

HTTP request logs containing /dashboard.. or /dashboard%2e%2e sequences targeting the Nezha dashboard
Successful HTTP 200 responses to requests for paths resembling /dashboard../data/config.yaml
Unexpected reads of data/config.yaml or other server-side files outside the admin-dist directory
Outbound traffic from hosts containing leaked credentials shortly after suspicious dashboard requests

Detection Strategies

Inspect reverse proxy and web server access logs for requests where the path matches the regex pattern ^/dashboard[^/] followed by traversal characters
Alert on responses serving YAML, environment, or key files from the Nezha process
Correlate dashboard requests originating from non-administrator source IP addresses with file access patterns

Monitoring Recommendations

Enable verbose HTTP logging on the Nezha dashboard and forward logs to a central analytics platform
Monitor file integrity on data/config.yaml and adjacent secret files for unexpected read access
Track the Nezha version field in inventory data to identify hosts running releases earlier than 2.0.13

How to Mitigate CVE-2026-53519

Immediate Actions Required

Upgrade all Nezha Monitoring deployments to version 2.0.13 or later without delay
Restrict network access to the Nezha dashboard using firewall rules or a VPN until patching is complete
Rotate any credentials, API tokens, and notification secrets stored in data/config.yaml on exposed instances
Review historical access logs for evidence of exploitation prior to remediation

Patch Information

The maintainers fixed the issue in Nezha Monitoring version 2.0.13. The patched release replaces the substring prefix check with a path-segment match and prevents traversal sequences from resolving outside the admin asset directory. Refer to the GitHub Security Advisory GHSA-5c25-7vpj-9mqh for release details.

Workarounds

Place the dashboard behind an authenticating reverse proxy that rejects URLs containing .. sequences
Configure a web application firewall rule to block requests matching /dashboard[^/] patterns
Bind the Nezha dashboard to localhost and require an SSH tunnel for administrative access until upgrade

bash

# Example nginx rule blocking traversal attempts against the Nezha dashboard
location ~* "^/dashboard[^/].*\.\." {
    return 403;
}