CVE-2026-77339Public exploitNetwork attack vectorHinoki check available

Process control via unauthenticated DNS-rebindable MCP listener

Published Sep 18, 2026 · Updated Sep 18, 2026

Origin-validation and authentication flaws in Process Compose before 1.120.0 allow remote attackers to control processes through a victim's browser. The MCP SSE listener accepts untrusted Host and Origin values and unauthenticated messages before dispatching requests to registered tools. MCP SSE must be enabled and the victim must visit an attacker-controlled site; exposed control or user-defined tools allow log access, process changes, and configured command execution.

CVSS severity5.1
Medium
EPSS probability0.26%
Next 30 days · Oct 19, 2026
Known exploitationUnconfirmed
Based on sourced intelligence
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Summary

What happened

Origin-validation and authentication flaws in Process Compose before 1.120.0 allow remote attackers to control processes through a victim's browser. The MCP SSE listener accepts untrusted Host and Origin values and unauthenticated messages before dispatching requests to registered tools. MCP SSE must be enabled and the victim must visit an attacker-controlled site; exposed control or user-defined tools allow log access, process changes, and configured command execution.

The record

CVE
CVE-2026-77339
Published
Sep 18, 2026
Updated
Sep 18, 2026
Vendor
F1bonacc1
Product
Process Compose
Classifications
CWE-346, CWE-306, T1189
Attack vector
network
Privileges
unauthenticated

Timeline

How it unfolded

  1. Sep 18, 2026CVE publishedPublication date reported by the CVE source.
  2. Sep 18, 2026Record updatedLatest update available in the CVE record.

Exploitability

Present is not the same as exploitable

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Is a vulnerable build present?

Compare these published version ranges with your installed build and any vendor patches.

  1. Affected versionversion=< 1.120.0

What conditions does exploitation require?

Attack vectornetwork
Required privilegesunauthenticated

What is affected?

F1bonacc1 · Process Composeversion=< 1.120.0

Published CVSS scores

5.1GitHubCVSS:4.0/AV:N/AC:L/AT:P/PR:N/UI:P/VC:L/VI:L/VA:N/SC:L/SI:H/SA:N

CVSS describes severity. EPSS estimates exploitation probability.

Attacks

What attackers are doing with it

Daily unique IPs observed by Shadowserver honeypots for known exploited vulnerabilities (KEVs). Missing observations do not establish an absence of attacks.

Activity data is delayed. The latest report is Sep 28, 2026.

Daily unique IPsNo honeypot observations are available for this CVE in the selected window.

No observations available

Sep 22, 2026Sep 28, 2026
Latest reporting daySep 28, 2026
Latest daily unique IPsUnavailable
Prior 30-day averageUnavailable
SourceShadowserver honeypots (KEV)
Vectornetwork
Privilegesunauthenticated
Known exploitationUnconfirmed
Public exploitPublished

Weakness, pattern, technique

CWE-346Origin Validation Error
CWE-306Missing Authentication for Critical Function
T1189Drive-by Compromise

Public exploit references

Labels summarize the accepted research assessment. They do not indicate a test against your environment.

Technologies

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Your stack

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