Siyuan — CraftedSignal Threat Feed

SiYuan Path Traversal via Double URL Encoding in `/export/` Endpoint

hello@craftedsignal.io — Wed, 22 Apr 2026 20:55:31 +0000

SiYuan is vulnerable to a path traversal vulnerability (CVE-2026-30869) due to a redundant url.PathUnescape() call within the serveExport() function. The vulnerability exists in versions prior to 3.6.5. This flaw allows an authenticated attacker, including low-privilege users with Publish/Reader roles, to bypass intended security restrictions and access sensitive files stored within the SiYuan workspace. The initial fix attempted with IsSensitivePath() proved insufficient as it did not address the core issue of double URL decoding. An attacker can exploit this vulnerability by using double URL encoded characters in a crafted HTTP request, allowing them to read arbitrary files such as the complete SQLite document database (siyuan.db), kernel logs, and other critical files.

Attack Chain

An authenticated attacker sends a GET request to the /export/ endpoint with a double URL encoded path, such as /export/%252e%252e/siyuan.db.
The Go HTTP server decodes the initial layer of URL encoding, transforming %25 into %, resulting in a path like /export/%2e%2e/siyuan.db.
The path cleaner does not recognize %2e%2e as directory traversal, so it passes through.
The serveExport() function then calls url.PathUnescape() on the path, decoding %2e%2e into ...
The filepath.Join() function concatenates the exportBaseDir with the now decoded path, e.g., /../siyuan.db.
The IsSensitivePath() check fails to block the request because it doesn’t account for the decoded path or specific database files in the temp/ directory.
The attacker successfully retrieves the contents of the siyuan.db file, which contains the complete document database.
The attacker repeats the process to access other sensitive files within the workspace, such as siyuan.log, blocktree.db, and asset_content.db.

Impact

Successful exploitation of this vulnerability allows an attacker to exfiltrate sensitive data, including the entire SQLite document database, potentially containing all user documents, attributes, and search indexes. The attacker can also access the kernel log, which may contain internal server paths, versions, configuration details, and error messages. This information disclosure could lead to further compromise of the system. While the number of victims is unknown, any SiYuan instance running a version prior to 3.6.5 is potentially vulnerable.

Recommendation

Upgrade SiYuan to version 3.6.5 or later to remediate the vulnerability.
Deploy the provided Sigma rule Detect SiYuan Path Traversal Attempt to detect attempts to exploit this vulnerability by monitoring for double URL encoded characters in requests to the /export/ endpoint.
Monitor web server logs for requests to the /export/ endpoint containing %252e%252e to identify potential exploitation attempts.
Consider implementing a more robust path validation mechanism within the serveExport() function that properly handles URL decoding and directory traversal attempts.

SiYuan Zero-Click NTLM Theft and Blind SSRF via Mermaid Diagrams

hello@craftedsignal.io — Sat, 11 Apr 2026 12:00:00 +0000

SiYuan, a note-taking application, is vulnerable to a zero-click NTLM hash theft and blind SSRF exploit due to insecure configuration of Mermaid.js. The application configures Mermaid.js with securityLevel: "loose" and htmlLabels: true, which allows tags with src attributes to bypass sanitization and be injected into SVG blocks. When a user opens a note containing a malicious Mermaid diagram with a protocol-relative URL (e.g., //attacker.com/image.png), the Electron client fetches the URL. On Windows, this resolves as a UNC path, triggering SMB authentication and sending the victim’s NTLMv2 hash to the attacker. On macOS and Linux, the same diagram triggers an HTTP request to the attacker’s server, exfiltrating the victim’s IP address. The vulnerability affects SiYuan versions prior to the fix implemented after April 7, 2026. This allows for credential theft without any user interaction beyond opening a note.

Attack Chain

The attacker crafts a malicious SiYuan note containing a Mermaid diagram with a protocol-relative URL within an tag, such as .
The attacker distributes the malicious note (e.g., via sharing or a crafted .sy export).
The victim opens the note in SiYuan.
SiYuan renders the Mermaid diagram using the insecure Mermaid.js configuration.
The SVG containing the malicious tag is injected into the DOM via innerHTML.
The Electron client attempts to fetch the resource at the protocol-relative URL.
On Windows, the protocol-relative URL resolves to a UNC path (\\attacker.com\share\img.png), initiating an SMB connection.
Windows automatically sends the victim’s NTLMv2 hash to the attacker’s SMB server, or makes an HTTP request leaking victim’s IP on other platforms.

Impact

The vulnerability allows for zero-click NTLMv2 hash theft on Windows systems, where the victim only needs to open a note containing the malicious Mermaid diagram. The stolen NTLMv2 hashes can be cracked offline or used in relay attacks to gain unauthorized access to the victim’s resources. On all platforms, this vulnerability can be exploited to perform blind SSRF and leak the victim’s IP address, acting as a tracking pixel to confirm when the note was opened. This affects all SiYuan users who receive a crafted note.

Recommendation

Deploy the Sigma rule Detect SiYuan Mermaid NTLM Theft Attempt to identify SMB traffic originating from SiYuan processes attempting to connect to external IPs (network_connection log source).
Deploy the Sigma rule Detect SiYuan Mermaid SSRF Attempt to detect HTTP requests from SiYuan to external IP addresses with a suspicious URL (network_connection log source).
Monitor network traffic for SMB connections originating from SiYuan, especially to unusual or external destinations (network_connection log source).
Block the attacker’s domain (attacker.com) at the DNS resolver, as observed in the malicious Mermaid diagram example (iocs).
Upgrade SiYuan to a patched version that addresses CVE-2026-40107 to mitigate the underlying vulnerability.

SiYuan Note Reflected XSS Vulnerability in SVG Processing

hello@craftedsignal.io — Wed, 01 Apr 2026 00:30:01 +0000

SiYuan Note, a note-taking application, is susceptible to a reflected XSS vulnerability in its dynamic icon generation functionality. This flaw, present in versions prior to commit f09953afc57a, arises from an insufficient sanitization of SVG content, specifically failing to account for namespace prefixes in SVG elements. The vulnerability resides in the /api/icon/getDynamicIcon endpoint, which is accessible without authentication. An attacker can exploit this by crafting a malicious SVG payload containing namespaced