CVE-2026-40289 MervinPraison CVE debrief

Who should care

Defenders responsible for PraisonAI and praisonaiagents deployments should assess exposure and prioritize patching vulnerable versions. This includes operators, platform administrators, vulnerability management teams, and security teams who need to review the affected scope, severity, and vendor guidance to validate affected scope and prioritize patching.

Why it matters

CVE-2026-40289 is a critical vulnerability in PraisonAI's browser bridge, allowing unauthenticated remote session hijacking. Defenders responsible for PraisonAI and praisonaiagents deployments should assess exposure and prioritize patching vulnerable versions.

• Unauthorized remote control of connected browser automation sessions
• Leakage of sensitive page context and automation results
• Misuse of model-backed browser actions

Technical summary

The browser bridge in PraisonAI versions below 4.5.139 and praisonaiagents versions below 1.5.140 is vulnerable to unauthenticated remote session hijacking due to missing authentication and a bypassable origin check on its /ws WebSocket endpoint. An attacker can connect to the /ws WebSocket endpoint, send a start_session message, and hijack an idle browser-extension WebSocket session. This enables unauthorized remote control of connected browser automation sessions, leakage of sensitive page context and automation results, and misuse of model-backed browser actions. Defenders should prioritize patching vulnerable versions of PraisonAI and praisonaiagents, and restrict access to the browser bridge.

Defensive priority

Defenders should prioritize patching vulnerable versions of PraisonAI and praisonaiagents, and restrict access to the browser bridge.

Recommended defensive actions

• Patch vulnerable versions of PraisonAI and praisonaiagents
• Restrict access to the browser bridge
• Monitor for suspicious activity on the /ws WebSocket endpoint
• Review compensating controls for exposed systems while remediation is scheduled and verified
• Check relevant monitoring, detection, and logs for exposed assets that need extra review
• Track exceptions, retest remediated assets, and close the item only after evidence is documented
• Confirm whether affected product deployments exist in managed environments and assign an owner for follow-up

Evidence notes

The CVE record and NVD vulnerability detail page provide information on the vulnerability, its impact, and affected versions. The browser bridge in PraisonAI versions below 4.5.139 and praisonaiagents versions below 1.5.140 is vulnerable to unauthenticated remote session hijacking due to missing authentication and a bypassable origin check on its /ws WebSocket endpoint. Defenders should verify the affected versions and assess exposure. The CVE Program record and NVD detail page offer source-provided metadata and vulnerability details.

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.