CVE-2025-51859

MEDIUM

Chaindesk thru 2025-05-26 - Stored Cross-Site Scripting via AI Agent System Prompt

Title source: llm
STIX 2.1

Exploitation Summary

EIP tracks 1 public exploit for CVE-2025-51859. PoCs published by Secsys-FDU.

AI-analyzed exploit summary This repository provides a detailed technical analysis of CVE-2025-51859, a Stored XSS vulnerability in Chaindesk's AI agent chat functionality, combined with an IDOR vulnerability. The writeup explains how an attacker can craft malicious AI agents to deliver XSS payloads via LLM-generated responses and exploit IDOR for unauthorized access.

Description

Stored Cross-Site Scripting (XSS) vulnerability in Chaindesk thru 2025-05-26 in its agent chat component. An attacker can achieve arbitrary client-side script execution by crafting an AI agent whose system prompt instructs the underlying Large Language Model (LLM) to embed malicious script payloads (e.g., SVG-based XSS) into its chat responses. When a user interacts with such a malicious agent or accesses a direct link to a conversation containing an XSS payload, the script executes in the user's browser. Successful exploitation can lead to the theft of sensitive information, such as JWT session tokens, potentially resulting in account hijacking.

Exploits (1)

nomisec WRITEUP
by Secsys-FDU · poc
https://github.com/Secsys-FDU/CVE-2025-51859

This repository provides a detailed technical analysis of CVE-2025-51859, a Stored XSS vulnerability in Chaindesk's AI agent chat functionality, combined with an IDOR vulnerability. The writeup explains how an attacker can craft malicious AI agents to deliver XSS payloads via LLM-generated responses and exploit IDOR for unauthorized access.

Classification
Writeup 95%
Attack Type
Xss
Complexity
Moderate
Reliability
Reliable
Target: Chaindesk (web application for AI agents)
No auth needed
Prerequisites: Ability to create a Chaindesk AI agent · Victim interaction with malicious agent or crafted URL
devstral-2 · analyzed Feb 18, 2026 Full analysis →

References (1)

Core 1
Core References

Scores

CVSS v3 6.5
EPSS 0.0042
EPSS Percentile 33.2%
Attack Vector NETWORK
CVSS:3.1/AV:N/AC:L/PR:N/UI:R/S:U/C:H/I:N/A:N

CISA SSVC

Vulnrichment
Exploitation poc
Automatable no
Technical Impact partial

Details

CWE
CWE-79
Status published
Published Jul 22, 2025
Tracked Since Feb 18, 2026