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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
2026-06-23
Advisory published
2026-06-19
Advisory updated
2026-06-23

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.

Sources and references

Verified primary and authoritative sources

  • CVE-2026-49357 CVE Program record

    Publisher, destination, and source semantics verified

    URL: https://www.cve.org/CVERecord?id=CVE-2026-49357

    CVE Program - Official CVE Program record with source-provided CVE metadata.

  • CVE-2026-49357 NVD vulnerability detail

    Publisher, destination, and source semantics verified

    URL: https://nvd.nist.gov/vuln/detail/CVE-2026-49357

    NIST National Vulnerability Database - Official NIST NVD detail page and source-specific vulnerability assessment.

Supplemental references

Methodology and review provenance

AI-assisted synthesis based on stored public vulnerability evidence. System validation, approval state, and publication status do not by themselves establish human review of this revision. PatchSiren helps prioritize defensive review and does not prove exposure or remediation on any system.