CVE-2026-77339
When MCP SSE is enabled, a malicious website can use DNS rebinding to reach the loopback listener and issue MCP requests.
Does this matter?
Lower severity and a low EPSS score (0.26%). Track it; it rarely justifies an emergency change on its own.
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.
- CVSS 4.0
- 5.1 MEDIUMCVSS:4.0/AV:N/AC:L/AT:P/PR:N/UI:P/VC:L/VI:L/VA:N/SC:L/SI:H/SA:N/E:X/CR:X/IR:X/AR:X/MAV:X/MAC:X/MAT:X/MPR:X/MUI:X/MVC:X/M
- EPSS
- 0.26% probability · 17th percentile
- Public exploits
- None in Exploit-DB
- CISA KEV
- Not listed
- Weakness
- CWE-306, CWE-346
- Source
- security-advisories@github.com
EPSS 0.3% since 26 October 2026; no change recorded yet. Points are recorded when the score first appears and whenever it moves by a percentage point or more.
References
- https://github.com/F1bonacc1/process-compose/commit/6ffa74f462cd2fa4f8dc1ee63c70b793b298c858
- https://github.com/F1bonacc1/process-compose/releases/tag/v1.120.0
- https://github.com/F1bonacc1/process-compose/security/advisories/GHSA-5gm3-9crp-6g3v
- https://github.com/F1bonacc1/process-compose/security/advisories/GHSA-5gm3-9crp-6g3v
Source: NVD record, EPSS from FIRST.org, KEV from CISA, exploits from Exploit-DB. Refreshed daily. Download this record as JSON.