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

Quick assessment

Affected
ThinkInAIXYZ deepchat
Exploitation
No confirmed in-the-wild exploitation; assess based on exposure
Recommended action
Check the vendor advisory and references for a fixed version. If immediate upgrade is impossible, restrict exposure and increase monitoring.

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

CVSS 9.6 · Critical EPSS 0.56% · P46

Possible ATT&CK Techniques 1 AI

T1203 · Exploitation for Client Execution

Affected Version Matrix 1

VendorProduct Version RangeStatus
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: CVE Program / CVE List V5
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: CVE Program / CVE List V5
CVSS Information
CVSS:3.1/AV:N/AC:L/PR:N/UI:R/S:C/C:H/I:H/A:H
Source: CVE Program / CVE List V5
Vulnerability Type
输入验证不恰当
Source: CVE Program / CVE List V5
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

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III. Intelligence Information for CVE-2026-43899

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Vendor Advisories for CVE-2026-43899 (1)

IV. Related Vulnerabilities

Same product: deepchat
Same vendor: ThinkInAIXYZ
Same weakness: CWE-20