Critical Input validation

CVE-2026-43899 — DeepChat: Electron Pop-up Handler Bypass Enables Arbitrary Protocol Execution

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.

Published May 11, 2026 · Updated Oct 13, 2026 · Sources: NIST National Vulnerability Database, CVE Program (cve.org) e CISA ADP · CNA: GitHub_M

Low

Who exploits it and how urgent it is

A 0–100 score combining confirmed exploitation, ransomware and APT use, public exploits, EPSS and severity.

No exploitation signal in the sources consulted so far.

How the score was calculated

EPSS 0.6% (30-day exploitation probability)+7
Technical severity (critical)+10
CISA SSVC: exploitation "poc"+5

The score orders the patch queue; it does not replace your asset context (internet exposure, criticality, compensating controls).

Triage

Is it exploited, how likely is exploitation, what does it touch, and how severe do the sources call it.

Exploitation

Not confirmed

Not in CISA KEV — an absence of record, not proof it is unexploited.

EPSS FIRST

0.56%

ahead of 45% of scored CVEs · Oct 14, 2026

Affects

ThinkInAIXYZ

Deepchat

CVSS base

9.6

Critical · 2 source(s)

CISA SSVC assessment CISA

Three decision points CISA publishes for the CVEs it assesses (SSVC 2.0.3). A stakeholder decision, not a severity score.

Exploitation

Proof of concept

none · proof-of-concept · active

Automatable

can an attacker script the kill-chain steps

Technical impact

Total

partial · total control of the vulnerable component

Remediation

Fixes and mitigations documented by the sources — linked to the original advisory.

No fix documented by the sources we poll. That does not mean none exists: check the vendor advisory.

First 24 hours

Ordered from the record’s own fields — exposure first, because you cannot patch what you have not found. A rule-generated starting point.

Identify exposed assets running the affected vendor/product/version combinations (ThinkInAIXYZ Deepchat).
The attack is network-based and needs no privileges: restrict exposure (ACLs, VPN, WAF) until patched.
No fix documented in the sources: reduce exposure and monitor the vendor advisory.
Exploitation requires user interaction: tighten email/web filtering and warn affected users.
Search available logs for exploit probes matching the vulnerability class (input validation), errors and authentication anomalies.

Affected scope

Vendor, product and versions as the sources word them.

Vendor	Product	Versions	Status	Source
ThinkInAIXYZ	Deepchat	version < 1.0.4-beta.1	Vulnerable	CVE Program (cve.org) e CISA ADP

Attack characteristics

The CVSS vector, decoded. It describes the attack, not your exposure to it.

Attack vector

Network

Attack complexity

Low

Privileges required

None

User interaction

Required

Scope

Changed

Confidentiality

High

Integrity

High

Availability

High

Every base score collected

Sources score independently and may disagree; each row says who scored it and under which version.

Score	Version	Severity	Expl.	Impact	Scored by
9.6	CVSS 3.1	Critical	2.8	6.0	security-advisories@github.com via NIST National Vulnerability Database
9.6	CVSS 3.1	Critical	—	—	GitHub_M via CVE Program (cve.org) e CISA ADP

CVSS:3.1/AV:N/AC:L/PR:N/UI:R/S:C/C:H/I:H/A:H (score shown at the top: security-advisories@github.com)

Weakness MITRE

Weakness class according to MITRE’s CWE catalog.

CWE-20 · Improper Input Validation

Other CVEs with this weakness →

EPSS over time FIRST

Oct 13, 2026 → Oct 14, 2026 · 2 reading(s) · max 0.56%

Detection

Read off the CVSS vector and the weakness class. Starting points, not tested rules.

Prioritize edge telemetry for the network-reachable component (proxy, WAF, IDS/IPS).

web/proxy/WAF logsnetwork IDS/IPS

Analysis and videos

CVE-2026-43899: DeepChat: Electron Pop-up Handler Bypass Enables Arbitrary Protocol Execution
CVE-2026-43899 affects DeepChat versions prior to v1.0.4-beta.1. The record describes an incomplete mitigation for CVE-2025-55733 that left native Electron pop-up handlers unsanitized, allowing a crafted Markdown link to reach shell.openExternal() and bypass the external URL validation. The CNA rates it critical with CVSS 3.1 score 9.6, and the fix is stated to be in v1.0.4-beta.1.

Timeline

What happened to this CVE, newest first.

2026
Affected products added · thinkinaixyz/deepchat
Oct 13, 2026 · CVE Program (cve.org) e CISA ADP
SSVC assessment updated
Oct 13, 2026 · CVE Program (cve.org) e CISA ADP
Record published
Oct 13, 2026
CVSS changed · 9.6
Oct 13, 2026 · NIST National Vulnerability Database
Source status changed · → Deferred
Oct 13, 2026 · NIST National Vulnerability Database
Record created in this database
Oct 13, 2026 · NIST National Vulnerability Database
CVE published
May 11, 2026 · GitHub_M

Source activity

Repeated readings are counted rather than listed.

1× Official description updated · Oct 13, 2026 – Oct 13, 2026

References

1 on the record

github.com/ThinkInAIXYZ/deepchat/security/advisories/GHSA-cp8j-jx7q-7r5f
x_refsource_CONFIRM, NIST National Vulnerability Database

Elsewhere on this site

ThinkInAIXYZ
every CVE for this vendor

Input validation
same class

CWE-20
other pages naming this weakness

Related CVEs (same products)

Critical CVE-2026-43900 DeepChat SVG Artifact XSS via Sanitizer Bypass (CVE-2026-43900) May 11, 2026
Critical CVE-2025-67744 Mermaid XSS vulnerability leads to Remote Code Execution Dec 15, 2025
Critical CVE-2025-66481 DeepChat's Incomplete XSS Fix Allows RCE through Mermaid Content Dec 8, 2025
Critical CVE-2025-66222 DeepChat Cross-Site Scripting(XSS) escalate to Remote Code Execution(RCE) Dec 3, 2025

Not in any source we poll

Listed rather than left blank: an empty field and an unmeasured one look identical on screen, and only one is a reason to look elsewhere.

No fixed version, patch or mitigation documented.
No confirmed IOCs, IP addresses, domains, file hashes, or malware artifacts supplied.
No organization-specific asset inventory, compensating-control status, or patch deployment evidence supplied.
No exploit packet captures, log samples, or incident case IDs supplied.

Answered from this record

Text assembled only from the fields above — no additional claims.

What should defenders know first?

CVE-2026-43899 is "DeepChat: Electron Pop-up Handler Bypass Enables Arbitrary Protocol Execution", rated Critical. It affects Deepchat (ThinkInAIXYZ); versions are in the scope table. It is not in CISA KEV, which does not rule out exploitation. CVSS 9.6 describes technical severity. EPSS 0.56% estimates the probability of exploitation in 30 days; neither replaces your asset context. First verify whether exposed or business-critical assets run the affected versions, apply vendor fixes or mitigations, and preserve logs for review.

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