CVE-2026-100868 penpot CVE debrief

Who should care

Defenders responsible for Penpot installations, especially those exposed to adjacent networks, should assess and mitigate this vulnerability. This includes reviewing system configurations, verifying the integrity of the MCP server plugin WebSocket bridge, and ensuring that appropriate security measures are in place to prevent exploitation. Additionally, security teams and vulnerability management teams should prioritize this vulnerability based on its CVSS

Why it matters

This vulnerability allows unauthenticated attackers to access and manipulate the Penpot MCP server plugin WebSocket bridge, potentially leading to data tampering and other security issues.

• Unauthenticated access to the WebSocket port
• Impersonation of the Penpot browser plugin
• Interception of task payloads and injection of forged results

Technical summary

The Penpot MCP server plugin WebSocket bridge is bound to all network interfaces without authentication in single-user mode. This allows unauthenticated attackers on adjacent networks to connect to the WebSocket port, impersonate the Penpot browser plugin, intercept task payloads, and return forged results to the MCP client. The vulnerability highlights the importance of securing network interfaces and implementing proper authentication mechanisms to prevent unauthorized access and potential data tampering within Penpot installations.

Defensive priority

Defenders should prioritize verifying and mitigating this vulnerability, especially in environments where Penpot is exposed to adjacent networks.

Recommended defensive actions

• Verify Penpot version and configuration
• Restrict network access to the WebSocket port
• Implement authentication for the WebSocket bridge
• Monitor for suspicious activity
• Review compensating controls for exposed systems
• Track exceptions and retest remediated assets
• Plan vendor-supported updates or mitigations through normal change control

Evidence notes

The CVE record and NVD entry provide details about the vulnerability, but additional information from the vendor and other sources is limited. Defenders should verify the vulnerability's impact on their systems, focusing on Penpot installations exposed to adjacent networks, and review available patches or mitigations. The lack of authentication in single-user mode for the MCP server plugin WebSocket bridge increases the risk of exploitation.

Sources and references

Methodology and review provenance

AI-assisted synthesis based on stored public vulnerability evidence. System validation, approval state, and publication status do not by themselves establish human review of this revision. PatchSiren helps prioritize defensive review and does not prove exposure or remediation on any system.