---
title: "CVE-2026-40289: PraisonAI Browser Server allows unauthenticated WebSocket clients to hijack connected extension sessions"
url: https://erroneo.us/security/cve/CVE-2026-40289/
description: "CVE-2026-40289 (praisonaiagents (PyPI)): PraisonAI is a multi-agent teams system. In versions below 4.5.139 of PraisonAI and 1.5.140 of praisonaiagents, the…"
type: vulnerability-record
section: "Security Digest"
date_published: 2026-04-14
date_modified: 2026-04-14
publisher: erroneo.us
author: erroneo.us Security Desk
cve: "CVE-2026-40289"
kev: false
cvss: 9.1
epss: 0.00521
license: All rights reserved. Quote with attribution and a link.
---

# CVE-2026-40289: PraisonAI Browser Server allows unauthenticated WebSocket clients to hijack connected extension sessions

**Signal:** Critical and remotely reachable. No known exploitation yet, but it is network-reachable without credentials. (Computed from CISA KEV, EPSS and CVSS; not an editorial verdict.)

## Should you act?

- Not in CISA KEV , but CISA’s SSVC assessment records a public proof-of-concept, so attack code exists.
- EPSS 0.5% , percentile 43: FIRST’s model estimates a 0.5% chance of exploitation activity in the next 30 days, higher than 43% of all scored CVEs (low). EPSS is a probability, not a verdict.
- Remotely reachable with no login and no user interaction. If the vulnerable service is exposed to the internet, prioritize it.
- Only applies if your dependency tree includes praisonaiagents (PyPI) <= 1.5.139, fixed in 1.5.140 ; PraisonAI (PyPI) <= 4.5.138, fixed in 4.5.139 . Check your lockfile, including transitive dependencies.

## What it is

PraisonAI is a multi-agent teams system. In versions below 4.5.139 of PraisonAI and 1.5.140 of praisonaiagents, the browser bridge (praisonai browser start) is vulnerable to unauthenticated remote session hijacking due to missing authentication and a bypassable origin check on its /ws WebSocket endpoint. The server binds to 0.0.0.0 by default and only validates the Origin header when one is present, meaning any non-browser client that omits the header is accepted without restriction. An unauthenticated network attacker can connect, send a startsession message, and the server will route it to the first idle browser-extension WebSocket (effectively hijacking that session) and then broadcast all resulting automation actions and outputs back to the attacker. 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 in any environment where the bridge is network-reachable. This issue has been fixed in versions 4.5.139 of PraisonAI and 1.5.140 of praisonaiagents.

## Affected packages

- PyPI `praisonaiagents` <= 1.5.139 → fixed: 1.5.140
- PyPI `PraisonAI` <= 4.5.138 → fixed: 4.5.139

## Affected products (CVE record)

- MervinPraison PraisonAI: < 4.5.139
- MervinPraison praisonaiagents: < 1.5.140

## Severity

- GitHub_M CVSS 3.1: 9.1 `CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:H/I:H/A:N`
- GitHub CVSS 3.1: 9.1 `CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:H/I:H/A:N`

## Exploitation

- CISA KEV: not listed (no confirmed in-the-wild exploitation known to CISA).
- CISA SSVC assessment: exploitation poc , automatable yes , technical impact total .
- FIRST EPSS (model of 2026-10-21): 0.52% probability of exploitation activity in the next 30 days; percentile 43.

## Sources

- [GitHub Advisory GHSA-8x8f-54wf-vv92](https://github.com/advisories/GHSA-8x8f-54wf-vv92)
- [CVE.org record CVE-2026-40289](https://www.cve.org/CVERecord?id=CVE-2026-40289)
- [NVD entry CVE-2026-40289](https://nvd.nist.gov/vuln/detail/CVE-2026-40289)
- [github.com](https://github.com/MervinPraison/PraisonAI/security/advisories/GHSA-8x8f-54wf-vv92)
- [github.com](https://github.com/MervinPraison/PraisonAI/releases/tag/v4.5.139)

---
Source page: https://erroneo.us/security/cve/CVE-2026-40289/ · Security Digest: https://erroneo.us/security/ · More: https://erroneo.us/llms.txt