CVE-2026-54066: SiYuan Path Traversal Vulnerability

CVE-2026-54066 Overview

CVE-2026-54066 is a path traversal vulnerability in SiYuan, an open-source personal knowledge management system. The flaw exists in the /assets/*path route prior to version 3.7.0. A previous patch for CVE-2026-41894 addressed the same root cause in the /export/ route but left the /assets/ route exposed. When SiYuan runs in publish mode on default port 6808, an unauthenticated remote attacker can read arbitrary files within WorkspaceDir by double-URL-encoding .. segments. Targeted files include conf/conf.json, temp/siyuan.db, temp/blocktree.db, and siyuan.log. The vulnerability is tracked as [CWE-22] Path Traversal.

Critical Impact
Unauthenticated remote attackers can read the AccessAuthCode SHA256 hash, API token, and sync keys stored in conf/conf.json, enabling full compromise of the publish mode instance.

Affected Products

SiYuan personal knowledge management system versions prior to 3.7.0
Instances running in publish mode with the anonymous read-only HTTP endpoint exposed
Default deployments listening on port 6808

Discovery Timeline

2026-06-24 - CVE-2026-54066 published to NVD
2026-06-25 - Last updated in NVD database

Technical Details for CVE-2026-54066

Vulnerability Analysis

The vulnerability resides in SiYuan's HTTP routing layer, specifically the handler servicing the /assets/*path route. SiYuan's publish mode exposes an anonymous, read-only HTTP endpoint intended to share notebooks publicly. The asset handler resolves request paths relative to WorkspaceDir without normalizing percent-encoded sequences before performing path traversal checks.

When a request contains double-URL-encoded .. segments such as %252e%252e%252f, the routing layer decodes the path once during HTTP parsing. The remaining encoded layer bypasses the traversal filter. The handler then performs a second decoding pass when constructing the filesystem path, restoring the .. sequences and resolving them against WorkspaceDir.

The maintainers previously fixed the identical class of bug for the /export/ route as CVE-2026-41894. That patch did not cover the /assets/ handler, leaving the same defect exploitable through a different endpoint.

Root Cause

The root cause is incomplete input validation. The sanitization logic checks for literal .. substrings after a single decoding pass instead of fully canonicalizing the request path. Double encoding defeats the check, allowing attacker-controlled path components to escape WorkspaceDir.

Attack Vector

The attack requires only network access to a SiYuan instance running in publish mode. The attacker sends a crafted GET request to /assets/ followed by double-URL-encoded traversal sequences pointing at sensitive workspace files. No authentication, user interaction, or local access is required. Successful exploitation discloses conf/conf.json, which contains the AccessAuthCode hash, the API token, and sync keys, enabling further account compromise and data exfiltration.

No verified proof-of-concept code is published in the references. The GitHub Security Advisory GHSA-p4m3-mgmm-c664 provides additional technical context.

Detection Methods for CVE-2026-54066

Indicators of Compromise

HTTP requests to /assets/ containing double-encoded sequences such as %252e%252e%252f or %252E%252E%252F
Access log entries showing /assets/ requests targeting filenames like conf.json, siyuan.db, blocktree.db, or siyuan.log
Outbound connections from unknown IP addresses to TCP port 6808 on hosts running SiYuan
Unexpected use of the AccessAuthCode or API token from new geolocations following suspicious /assets/ traffic

Detection Strategies

Inspect web server and reverse proxy logs for repeated percent-encoded characters (%25) inside /assets/ request paths
Decode request URIs at the WAF or proxy layer and alert on resolved paths containing .. after recursive decoding
Compare baseline file access patterns for WorkspaceDir against runtime telemetry to flag reads of configuration and database files served over HTTP

Monitoring Recommendations

Enable verbose HTTP access logging on SiYuan and any fronting reverse proxy, retaining full request URIs
Monitor for SiYuan version strings below 3.7.0 in asset inventories and patch management systems
Alert on any external access to TCP port 6808 from networks outside an approved publish-mode allowlist

How to Mitigate CVE-2026-54066

Immediate Actions Required

Upgrade all SiYuan instances to version 3.7.0 or later, which contains the official fix
Rotate the AccessAuthCode, API token, and sync keys stored in conf/conf.json after patching, assuming exposure
Restrict network access to TCP port 6808 to trusted networks until the upgrade is completed
Review HTTP access logs for prior exploitation attempts using double-encoded traversal sequences

Patch Information

The maintainers fixed CVE-2026-54066 in SiYuan 3.7.0 by extending the path sanitization applied to the /export/ route to the /assets/*path handler. Details are published in the GitHub Security Advisory GHSA-p4m3-mgmm-c664.

Workarounds

Disable publish mode until the upgrade to 3.7.0 is applied
Place SiYuan behind a reverse proxy that recursively URL-decodes request paths and blocks any resolved path containing ..
Bind the SiYuan service to localhost or a private interface and require VPN access for remote users

bash

# Example nginx rule to block double-encoded traversal on the /assets/ route
location /assets/ {
    if ($request_uri ~* "%25(2e|2E){2}") { return 403; }
    if ($request_uri ~* "\.\./") { return 403; }
    proxy_pass http://127.0.0.1:6808;
}