CVE-2026-43899 CRITICAL

CVE-2026-43899: DeepChat: Incomplete Fix for CVE-2025-55733 leads to Remote Code Execution via Markdown Links bypassing `isValidExternalUrl`

Vendor Thinkinaixyz
Product deepchat
Weakness CWE-20 · Input validation
Published May 11, 2026
Last update May 12, 2026

CVSS base score

9.6/10
Attack vector Network
Attack complexity Low
Privileges required None
User interaction Required
Confidentiality High
Integrity High

CVSS vector

CVSS:3.1/AV:N/AC:L/PR:N/UI:R/S:C/C:H/I:H/A:H

What the vulnerability does

01Description

DeepChat is an open-source artificial intelligence agent platform that unifies models, tools, and agents. Prior to v1.0.4-beta.1, An incomplete mitigation for CVE-2025-55733 leaves DeepChat vulnerable to an arbitrary protocol execution bypass (RCE). While the patch correctly restricted api.openExternal() inside the renderer's preload/index.ts script, it structurally neglected to sanitize native Electron pop-up window handlers. An attacker or a compromised AI endpoint returning a Markdown link can trigger a target="_blank" native window interception in tabPresenter.ts, which forwards the malicious URL directly to shell.openExternal(url) and completely bypasses the isValidExternalUrl security boundary. This vulnerability is fixed in v1.0.4-beta.1.

Key dates

02Disclosure timeline

May 11, 2026 CVE published
May 12, 2026 Record updated