Vulnerability · Published May 11, 2026 · Assigned by GitHub_M

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

Critical 9.6

In plain English

A critical-severity improper input validation in deepchat from ThinkInAIXYZ. Proof-of-concept exploit code is public. The chance it is exploited in the next 30 days is estimated at 0.4% (higher than 35% of all known vulnerabilities).

Severity (CVSS 3.1)9.6Critical

Exploit odds (30 days)0.4%top 65.4% of all CVEs

Exploited in the wildNo reportsCISA SSVC: poc

Attack toolingNoneno public tooling known

Official 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.

Affected products (as reported)

Vendor	Product	Versions
ThinkInAIXYZ	deepchat	< 1.0.4-beta.1

Weakness: CWE-20 · Vector: CVSS:3.1/AV:N/AC:L/PR:N/UI:R/S:C/C:H/I:H/A:H

References

https://github.com/ThinkInAIXYZ/deepchat/security/advisories/GHSA-cp8j-jx7q-7r5f x_refsource_CONFIRM