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CVE-2026-100868

Penpot before 2.18.0 Unauthenticated WebSocket Access via MCP Bridge

MEDIUM
6.3
CVSS Score
Published: September 27, 2026 at 01:09 PM UTC
Updated: October 8, 2026 at 04:17 PM UTC
2 products affected across 1 vendorPenpotMcp

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Severity
MEDIUM6.3
Exploit prediction
EPSS 0.5%
SSVC
PoC

Description

Penpot before 2.18.0 binds the MCP server plugin WebSocket bridge to all network interfaces without authentication in single-user mode. Unauthenticated attackers on adjacent networks can connect to the WebSocket port to impersonate the Penpot browser plugin, intercept task payloads, and return forged results to the MCP client.

Affected

Our own answer: ranges merged, affected separated from platform-only, with confidence and review flags.

Mcp· Penpotnpm
90%
0 ≤ v ≤ 2.15.40
Penpot· Penpot
90%
0 ≤ v < 2.18.00
Affected range stops below 2.18.0, so it looks safe — our inference, not a vendor statement

References (6)

Product
Source: [email protected]
https://github.com/penpot/penpot
Technical Description
Source: [email protected]
https://github.com/penpot/penpot/blob/1d2c37e52c733f74017d90b0fd1ae2d074a5c33d/mcp/packages/server/src/PluginBridge.ts#L52
Patch
Source: [email protected]
https://github.com/penpot/penpot/commit/b5274a44766d095247037be18c1d1918ac67ddeb
RelatedVendor Advisory
Source: [email protected]
https://github.com/penpot/penpot/security/advisories/GHSA-22qr-rp27-j9wm
Vendor Advisory
Source: [email protected]
https://github.com/penpot/penpot/security/advisories/GHSA-ch2q-6x56-qg5r
Third Party Advisory
Source: [email protected]
https://www.vulncheck.com/advisories/penpot-before-2.18.0-unauthenticated-websocket-access-via-mcp-bridge

SSVC — Action Prioritization

SSVCPoCNot automatablePartial impact

SSVC signals action urgency (what to patch first), separate from CVSS which measures severity.

CVSS

6.3MEDIUMVulnCheck
Attack Vector
ADJACENT_NETWORK
Complexity
LOW
Privileges
NONE
User Interaction
NONE
Scope
UNCHANGED
Confidentiality
LOW
Integrity
LOW
Availability
LOW
Vector?

Quick Info

StatusDEFERRED
CWE
CWE-1327

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