Streamlit Vulnerability Exposes Users to Cloud Account Takeover Attacks

A critical security flaw in Streamlit, the popular open-source framework for building data applications, has been discovered that could allow cybercriminals to execute cloud account takeover attacks and manipulate financial data systems.

The vulnerability, found in Streamlit’s file upload feature, demonstrates how a simple oversight in client-side validation can lead to devastating consequences for organizations using the platform for sensitive applications.

Discovery and Impact

Researchers at Cato Networks’ Application Security Research Team discovered the vulnerability in February 2025, revealing how threat actors could bypass file type restrictions in Streamlit’s st.file_uploader widget.

The flaw enabled attackers to upload malicious files to cloud instances running Streamlit applications, potentially gaining unauthorized access to sensitive systems.

The vulnerability’s impact extends beyond simple file uploads. In a proof-of-concept demonstration, researchers showed how attackers could manipulate stock market dashboards built with Streamlit, potentially influencing real-time trading behavior and causing widespread financial disruption.

By gaining control of misconfigured cloud instances, attackers could expose sensitive cloud data, modify backend files, and tamper with financial information.

The core issue stemmed from Streamlit’s reliance on client-side validation for file type restrictions.

While developers believed the type parameter in st.file_uploader provided security enforcement, the restriction was only applied in the browser via JavaScript, with no server-side validation to verify file types.

Using application security tools like Burp Suite, attackers could intercept and modify upload requests, changing file extensions during transit to bypass frontend restrictions.

This arbitrary file upload vulnerability could be combined with directory traversal attacks to overwrite critical system files, such as SSH authorized keys, enabling remote access to cloud infrastructure.

Streamlit acknowledged the issue quickly and released a patch in version 1.43.2 on March 11, 2025, introducing backend validation to enforce file-type restrictions.

However, despite Cato Networks’ requests for CVE classification, Streamlit maintained that the vulnerability was primarily a developer implementation issue rather than a framework security flaw.

This vulnerability highlights the risks associated with widely used open-source frameworks integrated across multiple platforms.

Streamlit, acquired by Snowflake in 2022, powers numerous applications including machine learning prototypes, healthcare analytics, and financial dashboards across various cloud environments.

Organizations using Streamlit applications should immediately update to version 1.43.2 or later and implement proper access controls, network restrictions, and file validation mechanisms to prevent similar attacks.

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