CVE-2026-43900

Critical

Published: 11 May 2026

Published

11 May 2026

Modified

12 May 2026

KEV Added

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Patch

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CVSS Score v3.1 9.3 CVSS:3.1/AV:N/AC:L/PR:N/UI:R/S:C/C:H/I:H/A:N

EPSS Score 0.0031 22.3th percentile

Risk Priority 70 floored blend · peak EPSS

Summary

CVE-2026-43900 is a critical-severity Cross-site Scripting (CWE-79) vulnerability. Its CVSS base score is 9.3 (Critical).

Operationally, exploitation aligns with the MITRE ATT&CK technique JavaScript (T1059.007); ranked at the 22.3th percentile by exploit likelihood (below the median); it is not currently listed in the CISA KEV catalog.

This vulnerability is AI-related — categorised as LLM Application Platforms; in the Other ATLAS/OWASP Terms risk domain.

OWASP Top 10 for Web (2025)

EU & UK References

🇪🇺 ENISA EUVD: EUVD-2026-29337

Vulnerability details

DeepChat is an open-source artificial intelligence agent platform that unifies models, tools, and agents. Prior to v1.0.4-beta.1, a Cross-Site Scripting (XSS) vulnerability exists due to a discrepancy between the backend validation layer and the frontend browser rendering engine. The SVGSanitizer…

(src/main/lib/svgSanitizer.ts) restricts script execution by scrubbing javascript: protocols using plain-text regular expressions. However, it fails to account for HTML entity decoding prior to Vue's v-html DOM insertion inside the SvgArtifact.vue component. By feeding an SVG artifact with obfuscated entities (e.g., javascript:alert(1)), an attacker can completely bypass the sanitizer, culminating in arbitrary JavaScript execution when a victim interacts with the rendered SVG Element. This vulnerability is fixed in v1.0.4-beta.1.

CWE(s): CWE-79

AI Security AnalysisAI

AI Category: LLM Application Platforms
Risk Domain: Other ATLAS/OWASP Terms
OWASP Top 10 for LLMs 2025: None mapped
Classification Reason: Matched keywords: artificial intelligence

Related Threats

MITRE ATT&CK Enterprise TechniquesAI

T1059.007 JavaScript Execution

Adversaries may abuse various implementations of JavaScript for execution.

attack.mitre.org →

T1203 Exploitation for Client Execution Execution

Adversaries may exploit software vulnerabilities in client applications to execute code.

attack.mitre.org →

Why these techniques?

XSS sanitizer bypass directly enables arbitrary JavaScript execution in the victim's browser (T1059.007) via exploitation of a client-side vulnerability (T1203).

Confidence: HIGH · MITRE ATT&CK Enterprise v19.0