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Medium, CVSS 5.1amended

Process Compose: Browser DNS rebinding lets websites control local process-compose MCP tools

CVE-2026-77339GHSA-5gm3-9crp-6g3v

What to do

Vendor fix available. Upgrade each affected package to the fixed version on its release line (github.com/f1bonacc1/process-compose 1.120.0), redeploy, then verify what is actually installed.

This page has no inventory attached, so it cannot say whether you are affected. A vendor fix is not proof that your deployment is fixed.

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Affected packages

Sources

Severity and exploitation
Exploitation
No confirmed exploitation recorded. Patch Next marks exploitation only from CISA KEV.
CVSS 4.0
5.1 · 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 · score source
EPSS
  • CVE-2026-77339: 0.26% estimated exploitation activity in the next 30 days; percentile 17.30 (FIRST EPSS, 2026-11-03). This is a model estimate, not proof of exploitation or customer exposure.
Source description

As published by the source; long descriptions are shortened.

Summary A malicious website can use DNS rebinding to control a developer's local process-compose MCP SSE listener when MCP SSE is enabled. The vulnerable path accepts browser-origin requests before any Host validation, Origin validation, or caller-secret check, then dispatches the requests into process-compose MCP tools. This advisory covers https://github.com/F1bonacc1/process-compose, confirmed at commit d56aa59df04b72f8644811ac581a051bec05e485. The issue is in the MCP SSE transport, not the Gin REST API. The REST API token middleware protects REST routes, but the MCP listener is started separately and does not inherit that protection. Affected Code Root cause: Impact surface: Reproduction Start process-compose from the affected commit with MCP SSE and built-in control tools enabled: In a second terminal, emulate the browser request shape produced by DNS rebinding. A real attacker page keeps Host: attacker.example:8081 and Origin: http://attacker.example:8081 while the hostname…

Dates and revisions
Published by the source
Last modified by the source
Source last checked
  1. Revision 4 · amended ·

    Amended from ghsa record GHSA-5gm3-9crp-6g3v

  2. Revision 3 · amended ·

    Reviewed OSV alias/range/CVSS4 correction; package source scopes and original publication preserved. No customer finding resolved.

  3. Revision 2 · amended ·

    Amended from osv record GO-2026-6515

  4. Revision 1 · created ·

    Published from osv record GHSA-5gm3-9crp-6g3v

Agent brief

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# Patch Next advisory brief: CVE-2026-77339

Advisory: Process Compose: Browser DNS rebinding lets websites control local process-compose MCP tools
IDs: CVE-2026-77339, GHSA-5gm3-9crp-6g3v
Record: https://patchnext.com/advisories/cve-2026-77339 (revision 4, source checked 26 Oct 2026, 15:29 UTC)
Inventory: none attached. This brief comes from a public page and does not say whether any deployment is affected.
Severity: Medium (CVSS 5.1)
Exploitation: no confirmed exploitation recorded. Patch Next confirms exploitation only from CISA KEV.
Vendor response: Vendor fix available; fixed versions by package: github.com/f1bonacc1/process-compose 1.120.0. A vendor fix does not mean a deployment is fixed.

## Affected components
- Go github.com/f1bonacc1/process-compose: affected < 1.120.0; fixed in 1.120.0

## Suggested inspection (read-only)
- Go github.com/f1bonacc1/process-compose: check the installed version with your package manager.

## Supported action
Upgrade each affected component to a fixed version on its release line. For a transitive dependency, upgrade the parent package or add an override or constraint, then regenerate the lockfile. Redeploy every environment that ran an affected version.

## Required regression checks
- Run the test suite and a production build.
- Exercise the features that depend on github.com/f1bonacc1/process-compose.
- Repeat the inspection and confirm that only fixed versions remain installed.

## Rollback considerations
- Keep the previous lockfile and deployment artifact. Rolling back reinstates the vulnerable version, so apply any documented mitigation while you fix forward.

## Unresolved questions
- Which deployments run an affected version?
- Exploitation status can change. Check again before lowering the priority.
- Mark the work resolved only after the fixed version is verified in production.

## Sources
- Verified: https://osv.dev/vulnerability/GHSA-5gm3-9crp-6g3v (OSV record GHSA-5gm3-9crp-6g3v lists affected ranges: Go github.com/f1bonacc1/process-compose >=0 <1.120.0 (fixed))
- Verified: https://osv.dev/vulnerability/GO-2026-6515 (OSV record GO-2026-6515 lists affected ranges: Go github.com/f1bonacc1/process-compose >=0 <1.120.0 (fixed))
- Verified: https://github.com/advisories/GHSA-5gm3-9crp-6g3v (GitHub-reviewed advisory GHSA-5gm3-9crp-6g3v lists affected ranges: Go github.com/f1bonacc1/process-compose >=0 <1.120.0)

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