CVE-2026-77339

MEDIUMPre-NVD 5.15.1—
EchelonGraph scoreMEDIUM confidence

This medium-severity CVE scores 5.1 under a secondary CVSS source (NVD's own analysis pending). EPSS exploit probability: 0.2%, top 88% of all CVEs by exploit prediction. GitHub Security Advisory data not yet ingested — confidence will rise once GHSA publishes (typical lag: hours to days for open-source ecosystem CVEs; never for infrastructure-only CVEs).

Triggered by: NVD CVSS baseline
Sources: epss, secondary
Elevated
5.1EG
EchelonGraph verdictMonitorLow exploitation likelihood right now — keep watching.
  • Lower severity and no public exploit yet
CISA-KEV: Not listedEPSS PROB: 0%CVSS: 5.1Exploit: Elevated riskExposed: 0

No vendor fix yet — apply a workaround or compensating control (WAF / firewall / segmentation) and watch for a patch.

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 v3
5.1
EG Score
5.1(medium)
EG Risk
39(Track)
EG Risk 39/100SSVC: Track

EG Risk is EchelonGraph's 0–100 priority score: it fuses intrinsic severity with real-world exploitation and automatability so you can rank equal-severity CVEs and fix the most dangerous first. Higher = act sooner. Distinct from the 0–10 EG Score (severity).

How it’s computed
Severity51% × 45%
Exploitation40% × 40%
Automatability0% × 15%
Action: Routine — remediate on your standard cadence.
EPSS PROB
0%
EPSS %ILE
12%
KEV
Not listed

Published

September 18, 2026

Last Modified

September 18, 2026

Advisory Details (3)

Auto-updated Sep 18, 2026
🔬 Proof of concept available. Patch available. Sources: github, github_commit, github_release.
github_release Patch Available

v1.120.0

Patch available: F1bonacc1/process-compose v1.120.0

https://github.com/F1bonacc1/process-compose/releases/tag/v1.120.0
github_commit

commit 6ffa74f462cd (F1bonacc1/process-compose)

Fix landed in F1bonacc1/process-compose commit 6ffa74f462cd — awaiting tagged release

https://github.com/F1bonacc1/process-compose/commit/6ffa74f462cd2fa4f8dc1ee63c70b793b298c858
github Patch Available🟡 PoC Available

Browser DNS rebinding lets websites control local process-compose MCP tools · Advisory · F1bonacc1/process-compose · GitHub

https://github.com/F1bonacc1/process-compose/security/advisories/GHSA-5gm3-9crp-6g3v

Vendor Advisories for CVE-2026-77339(1)

These vendors published their own advisory mentioning this CVE — often with vendor-specific remediation steps + affected product lists not in NVD.

Weakness Classification(2)

MITRE Common Weakness Enumeration — the root-cause categories this CVE belongs to.

Data Freshness Timeline

(refreshed 5× in last 7d / 5× in last 30d)

Each row is a source pipeline that fetched or updated this CVE on that date, with what changed. For example, "NVD update" means NVD published or revised its analysis for this CVE; "MITRE cvelistV5" means we ingested or refreshed it from the CNA feed. Most recent first.

  1. 2026-09-19 17:27 UTCEG score recompute
  2. 2026-09-18 17:26 UTCEG score recompute
  3. 2026-09-18 16:54 UTCEG score recompute
  4. 2026-09-18 16:49 UTCEG score recompute
  5. 2026-09-18 16:49 UTCMITRE cvelistV5first tracked

Frequently asked(5)

What is CVE-2026-77339?
CVE-2026-77339 is a medium vulnerability published on September 18, 2026. 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…
When was CVE-2026-77339 disclosed?
CVE-2026-77339 was first published in the National Vulnerability Database on September 18, 2026. EchelonGraph re-ingests CVE updates from NVD on a 2-hour cycle, so this page reflects the latest published state.
Is CVE-2026-77339 actively exploited?
CVE-2026-77339 is not currently on CISA's Known Exploited Vulnerabilities catalog. FIRST EPSS estimates a 0% probability of exploitation in the next 30 days, which ranks it in the top 88.0% of all scored CVEs.
What is the CVSS score of CVE-2026-77339?
CVE-2026-77339 has a CVSS v3 base score of 5.1 (NVD).
How do I remediate CVE-2026-77339?
Patch to the fixed version published by the affected vendor. Where vendor advisories exist for CVE-2026-77339, EchelonGraph cross-links them in the Vendor Advisories panel below — those typically contain the canonical remediation steps, fixed version numbers, and any vendor-specific mitigations.

Dependency Blast Radius

Explore the affected products and dependency analysis for CVE-2026-77339

Explore →

Is Your Infrastructure Affected by CVE-2026-77339?

EchelonGraph automatically scans your cloud infrastructure and maps CVE exposure using blast radius analysis.

Start Free Scan →Browse All CVEs