# CVE-2026-49384: JetBrains PyCharm stored XSS in Jupyter notebook Markdown cells

Source: https://junglewise.ai/threats/cve-2026-49384-jetbrains-pycharm-stored-xss-in-jupyter-notebook-markdown-cells  
Publisher: Junglewise Threat Intelligence, https://junglewise.ai/threats  
Published: 2026-05-29. Updated: 2026-05-29  
License: CC BY 4.0 with a link back

CVE-2026-49384 · Severity: medium · CVSS 6.1 · Published 2026-05-29

JetBrains PyCharm, a popular integrated development environment (IDE) for Python developers, was vulnerable to a security flaw in how it handles Jupyter notebooks. An attacker could create a malicious notebook that, when opened by a user, executes unauthorized scripts within the IDE interface. This could lead to the theft of sensitive information or unauthorized actions performed on behalf of the user.

Technologies: [Jetbrains PyCharm](https://junglewise.ai/threats/technologies/pycharm). Vendors: [Jetbrains](https://junglewise.ai/threats/vendors/jetbrains).

## Quick answers

**Is CVE-2026-49384 exploited in the wild?** No. Junglewise Threat Intelligence has no report of CVE-2026-49384 being exploited in the wild.

**How severe is CVE-2026-49384?** Medium severity, with a CVSS score of 6.1, published 29 May 2026.

**Which products and versions are affected?** Jetbrains PyCharm before 2025.3.4.

**Is there a fix for CVE-2026-49384?** No fixed version is recorded yet. Check the vendor's advisory in the references below. If you run it, Junglewise drafts a mitigation that fits your setup and applies it once you approve, with senior security engineers behind it.

**How is CVE-2026-49384 attacked?** It is attacked over the network, in a network appliance.

**Am I affected by CVE-2026-49384?** Check whether you run Jetbrains PyCharm at an affected version. Junglewise does that check for you around the clock: connect your code, cloud and domains, and it matches new vulnerabilities like this one against what you actually run and tells you when one reaches you.

## Technical details

A stored cross-site scripting (XSS) vulnerability exists in JetBrains PyCharm versions prior to 2025.3.4. The flaw is located in the rendering of Markdown cells within Jupyter notebooks, where the application fails to properly neutralize user-supplied input (CWE-79). An attacker can exploit this by distributing a specially crafted .ipynb file; when a victim opens the file and the Markdown cell is rendered, malicious JavaScript executes in the context of the IDE's internal web view. This requires user interaction (opening the file) but no prior authentication. The vulnerability has been addressed in PyCharm version 2025.3.4.

## Affected products

- JetBrains PyCharm before 2025.3.4

## Timeline

- 2026-05-29: advisory: CVE-2026-49384 published by JetBrains

## References

- [https://www.jetbrains.com/privacy-security/issues-fixed/](https://www.jetbrains.com/privacy-security/issues-fixed/)

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