PatchSiren cyber security CVE debrief
CVE-2026-49357 dtwang CVE debrief
CVE-2026-49357 is a high-severity vulnerability in the Line Desktop MCP project, which enables users to operate the LINE Desktop application on Windows or Mac via MCP. The vulnerability arises from the `--http-mode` Streamable HTTP transport, which exposes the MCP `/mcp` endpoint without authentication. This allows any network client that can reach the port to initialize a session, list tools, and call tools that read LINE Desktop chat history or send LINE messages through the already logged-in desktop application. The vulnerability has a CVSS score of 8.8 and is considered HIGH severity. Defenders should prioritize patching to limit exposure.
- Vendor
- dtwang
- Product
- line-desktop-mcp
- CVSS
- HIGH 8.8
- CISA KEV
- Not listed in stored evidence
- Original CVE published
- 2026-06-19
- Original CVE updated
- 2026-06-22
- Advisory published
- 2026-06-19
- Advisory updated
- 2026-06-22
Who should care
Organizations using Line Desktop MCP, especially those with sensitive chat history or messaging functionality, should prioritize patching to prevent unauthorized access. Additionally, defenders responsible for securing network ports and monitoring for suspicious activity should be aware of this vulnerability.
Technical summary
The Line Desktop MCP project, unaffiliated with the official line-bot-mcp-server, supports a `--http-mode` Streamable HTTP transport for use with clients like n8n. In this mode, the server binds to `0.0.0.0` and exposes the MCP `/mcp` endpoint without an MCP-layer authentication check. Prior to version 1.1.2, any network client that can reach the port can initialize a session, list tools, and call tools that read LINE Desktop chat history or send LINE messages through the already logged-in desktop application. The vulnerability is fixed in version 1.1.2.
Defensive priority
High priority due to unauthenticated access and potential for sensitive data exposure.
Recommended defensive actions
- Apply the patch by updating to version 1.1.2 or later
- Inventory and review network-exposed Line Desktop MCP instances
- Limit exposure by restricting access to the MCP port
- Monitor for suspicious activity on the MCP port
- Review and update compensating controls for network security
Evidence notes
The primary evidence for this vulnerability comes from the CVE record and the NVD detail page. The vulnerability affects Line Desktop MCP versions prior to 1.1.2. Defenders should verify the version of Line Desktop MCP in use and check for any exposed instances on the network.
Official resources
This article is AI-assisted and based on the supplied source corpus.