Is CVE-2026-123854 exploited in the wild?

No. Junglewise Threat Intelligence has no report of CVE-2026-123854 being exploited in the wild.

How severe is CVE-2026-123854?

Medium severity, with a CVSS score of 5.5, published 6 November 2026.

Which products and versions are affected?

Jetbrains PyCharm before 2026.3.

Is there a fix for CVE-2026-123854?

Yes: fixed in PyCharm 2026.3. Junglewise finds every place you run it, drafts the upgrade and applies it once you approve.

How is CVE-2026-123854 attacked?

It is attacked with local access, in a web application.

Am I affected by CVE-2026-123854?

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.

CVE-2026-123854: JetBrains PyCharm code execution via crafted Jupyter notebook widget

CVE-2026-123854 · Severity: medium · CVSS 5.5 · Published 2026-11-06

JetBrains PyCharm is a Python IDE used by developers to write and test code. A vulnerability allows an attacker to execute arbitrary code even when PyCharm's Safe Mode is enabled, by crafting a malicious Jupyter notebook with a malicious widget module. An attacker who tricks a developer into opening a crafted notebook gains the ability to run code with the privileges of the PyCharm process.

Technologies: Jetbrains PyCharm. Vendors: Jetbrains.

Quick answers

Is CVE-2026-123854 exploited in the wild?: No. Junglewise Threat Intelligence has no report of CVE-2026-123854 being exploited in the wild.
How severe is CVE-2026-123854?: Medium severity, with a CVSS score of 5.5, published 6 November 2026.
Which products and versions are affected?: Jetbrains PyCharm before 2026.3.
Is there a fix for CVE-2026-123854?: Yes: fixed in PyCharm 2026.3. Junglewise finds every place you run it, drafts the upgrade and applies it once you approve.
How is CVE-2026-123854 attacked?: It is attacked with local access, in a web application.
Am I affected by CVE-2026-123854?: 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.

How to fix

Fixed in: PyCharm 2026.3

Technical details

Safe Mode bypass in JetBrains PyCharm allows arbitrary code execution through a crafted Jupyter notebook widget module. The vulnerability affects the Jupyter notebook integration component and requires user interaction (opening a malicious notebook file). An attacker can execute arbitrary code within the IDE process despite Safe Mode protections being enabled.

Affected products

JetBrains PyCharm before 2026.3

Timeline

2026-11-06: disclosed
2026-11-06: patched

References

https://www.jetbrains.com/privacy-security/issues-fixed/

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