CVE-2026-43899— DeepChat: Incomplete Fix for CVE-2025-55733 leads to Remote Code Execution via Markdown Links bypassing `isValidExternalUrl`
Possible ATT&CK Techniques 1AI
T1203 · Exploitation for Client ExecutionAffected Version Matrix 1
| Vendor | Product | Version Range | Status |
|---|---|---|---|
| ThinkInAIXYZ | deepchat | < 1.0.4-beta.1 | affected |
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I. Basic Information for CVE-2026-43899
Vulnerability Information
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Vulnerability Title
DeepChat: Incomplete Fix for CVE-2025-55733 leads to Remote Code Execution via Markdown Links bypassing `isValidExternalUrl`
Source: NVD (National Vulnerability Database)
Vulnerability Description
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.
Source: NVD (National Vulnerability Database)
CVSS Information
CVSS:3.1/AV:N/AC:L/PR:N/UI:R/S:C/C:H/I:H/A:H
Source: NVD (National Vulnerability Database)
Vulnerability Type
输入验证不恰当
Source: NVD (National Vulnerability Database)
Vulnerability Title
DeepChat 输入验证错误漏洞
Source: CNNVD (China National Vulnerability Database)
Vulnerability Description
DeepChat是ThinkInAIXYZ开源的一款智能助手。 DeepChat v1.0.4-beta.1之前版本存在输入验证错误漏洞，该漏洞源于对CVE-2025-55733的不完全缓解措施，虽然补丁正确限制了渲染器中的api.openExternal()，但结构上忽略了清理原生Electron弹出窗口处理程序，攻击者或受损AI端点返回的Markdown链接可触发target=_blank原生窗口拦截，将恶意URL直接转发给shell.openExternal(url)并完全绕过isValidExte
Source: CNNVD (China National Vulnerability Database)
CVSS Information
N/A
Source: CNNVD (China National Vulnerability Database)
Vulnerability Type
N/A
Source: CNNVD (China National Vulnerability Database)
Affected Products
| Vendor | Product | Affected Versions | CPE | Subscribe |
|---|---|---|---|---|
| ThinkInAIXYZ | deepchat | < 1.0.4-beta.1 | - |
II. Public POCs for CVE-2026-43899
| # | POC Description | Source Link | Shenlong Link |
|---|
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IV. Related Vulnerabilities
Same product: deepchat
- CVE-2026-43900
DeepChat: Persistent DOM XSS via HTML Entity Encoding in `<a - CVE-2025-67744
Mermaid XSS vulnerability leads to Remote Code Execution - CVE-2025-66481
DeepChat's Incomplete XSS Fix Allows RCE through Mermaid Con - CVE-2025-66222
DeepChat Cross-Site Scripting(XSS) escalate to Remote Code E - CVE-2025-58768
DeepChat's Mermaid rendering has XSS leading to RCE
Same vendor: ThinkInAIXYZ
- CVE-2026-43900
DeepChat: Persistent DOM XSS via HTML Entity Encoding in `<a - CVE-2025-67744
Mermaid XSS vulnerability leads to Remote Code Execution - CVE-2025-66481
DeepChat's Incomplete XSS Fix Allows RCE through Mermaid Con - CVE-2025-66222
DeepChat Cross-Site Scripting(XSS) escalate to Remote Code E - CVE-2025-58768
DeepChat's Mermaid rendering has XSS leading to RCE
Same weakness: CWE-20
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Microsoft Edge (Chromium-based) Security Feature Bypass Vuln - CVE-2026-45317
Open WebUI: Cross-Site Request Forgery (CSRF) via Image URL - CVE-2025-29936
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V. Comments for CVE-2026-43899
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