EUVD-2025-210289
GHSA-jv86-v5fr-xvg6
Severity by source
CVSS:4.0/AV:N/AC:L/AT:N/PR:N/UI:A/VC:N/VI:N/VA:N/SC:L/SI:L/SA:N/E:X/CR:X/IR:X/AR:X/MAV:X/MAC:X/MAT:X/MPR:X/MUI:X/MVC:X/MVI:X/MVA:X/MSC:X/MSI:X/MSA:X/S:X/AU:X/R:X/V:X/RE:X/U:X
PR:N because chat submission requires no account; UI:R because a human victim must view the chat; S:C because injected script executes in the victim's distinct browser security context.
Primary rating from Vendor (VulnCheck).
CVSS VectorVendor: VulnCheck
CVSS:4.0/AV:N/AC:L/AT:N/PR:N/UI:A/VC:N/VI:N/VA:N/SC:L/SI:L/SA:N/E:X/CR:X/IR:X/AR:X/MAV:X/MAC:X/MAT:X/MPR:X/MUI:X/MVC:X/MVI:X/MVA:X/MSC:X/MSI:X/MSA:X/S:X/AU:X/R:X/V:X/RE:X/U:X
Lifecycle Timeline
3DescriptionCVE.org
Flowise before 3.0.8 contains a cross-site scripting (XSS) vulnerability caused by insufficient input filtering in chat messages and custom agent functions. An attacker can inject malicious JavaScript by sending an iframe payload (e.g., <iframe src="javascript:alert(document.cookie)">) in a chat box, or by having a custom agent function return an XSS payload from an external website. The injected script executes in the victim's browser, enabling theft of cookies and session data.
AnalysisAI
Cross-site scripting in Flowise before 3.0.8 allows unauthenticated network attackers to inject malicious JavaScript into the chat interface via iframe javascript: URI payloads, or indirectly via custom agent functions that fetch and render unsanitized external HTTP responses. When a victim browses the affected chat or agent output in their browser, the injected script executes in their session, enabling cookie theft and session hijacking. A working proof-of-concept payload is publicly documented in GitHub Security Advisory GHSA-4fr9-3x69-36wv; no active exploitation is confirmed in CISA KEV at time of analysis.
Technical ContextAI
Flowise is an open-source, Node.js/npm-based visual AI workflow builder distributed under cpe:2.3:a:flowise:flowise:*:*:*:*:*:*:*:*. The root cause is CWE-80 (Improper Neutralization of Script-Related HTML Tags in a Web Page): the application fails to sanitize HTML and JavaScript before rendering it in the browser, allowing javascript: URI schemes and arbitrary HTML tags to execute as code. Two distinct injection surfaces exist: the chat interface directly renders unsanitized user-submitted messages, and the Agentflow custom function pipeline fetches external URLs via node-fetch and returns their raw text content to the renderer without sanitization - creating a second-order XSS path where attacker-controlled external web servers can deliver payloads through trusted agent execution.
RemediationAI
Upgrade Flowise to version 3.0.8 or later, the vendor-released patch confirmed by GHSA-4fr9-3x69-36wv and corroborated by EUVD and VulnCheck. Install via npm with 'npm install flowise@3.0.8' or equivalent. If immediate patching is blocked, restrict access to the Flowise chat interface and Agentflow creation capabilities to authenticated, trusted users only - this reduces but does not eliminate the attack surface, as authenticated users could still inject payloads targeting other users. As an additional defense-in-depth measure, deploy a Content Security Policy (CSP) header that sets 'script-src' to disallow inline scripts and blocks javascript: URI schemes; this would neutralize the specific iframe javascript: PoC payload but is not a substitute for patching and may break legitimate Flowise functionality requiring testing. The vendor advisory is at https://github.com/FlowiseAI/Flowise/security/advisories/GHSA-4fr9-3x69-36wv.
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Same weakness CWE-80 – Basic XSS
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External POC / Exploit Code
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