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

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CRITICAL

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

Published May 11, 2026

9.6

CRITICAL

CVSS 3.1

EPSS 0.56%

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

Vendor ThinkInAIXYZ Product Deepchat Default
n/a
- Version
  < 1.0.4-beta.1
  Status
  affected
  Constraints
  -

Default status is the baseline for the product, each version can override it (e.g. patched versions marked unaffected).

Vendor

Product

Default status

Versions

ThinkInAIXYZ

Deepchat

n/a

Version	Status	Constraints
< 1.0.4-beta.1	affected	-

Remediation

No remediation recorded yet.

Weaknesses (1)

CWE-20

Improper Input Validation

References (2)

https://euvd.enisa.europa.eu/vulnerability/EUVD-2026-29336
Advisory
https://github.com/ThinkInAIXYZ/deepchat/security/advisories/GHSA-cp8j-jx7q-7r5f
exploitx_refsource_CONFIRM

Link	Providers	Tags
https://euvd.enisa.europa.eu/vulnerability/EUVD-2026-29336		Advisory
https://github.com/ThinkInAIXYZ/deepchat/security/advisories/GHSA-cp8j-jx7q-7r5f		exploitx_refsource_CONFIRM