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CVE-2026-123854VulnerabilityPublished

In JetBrains PyCharm before 2026.3 code execution was possible in Safe Mode via a crafted Jupyter notebook widget

Source GCVE Database

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Authoritative record:CVE-2026-123854· Medium 5.5

Not known to be exploited · CVSS 5.5 Medium : upgrade to 2026.3 when convenient.

Data as of 6 Nov 2026, 19:05 UTC

CVSS 3.1 base score
5.5Medium
How severe the flaw is on the 0–10 CVSS scale.

Thin evidence

One scorer or none
CVSS scores by source
CNA (JetBrains)CVSS 3.15.5
Patch
Available – fixed in 2026.3
CVSS:3.1/AV:L/AC:L/PR:N/UI:R/S:U/C:H/I:N/A:N

Exploitation evidence

  1. Disclosed: evidence found.

    CVE published 6 Nov 2026

  2. Detectable: no evidence on record.

    No public nuclei template indexed

  3. Weaponized: no evidence on record.

    No public exploit code indexed in Metasploit or Exploit-DB

  4. Exploited in the wild: no evidence on record.

    Not in CISA KEV and no source reports exploitation

  5. Observed by OffSeq Mirage: no evidence on record.

    No attack traffic recorded by OffSeq Mirage sensors

A missing step is not evidence of safety. Sources: cve.org (opens in a new tab), the Metasploit, Exploit-DB and nuclei-templates index as of 6 Nov 2026.

What to do

Upgrade PyCharm to 2026.3.

Affected software

ProductAffectedFixed in
JetBrainsPyCharmAffected
  • <2026.3
Fixed in
  • 2026.3

AI-suggested

If you cannot patch yet, avoid opening untrusted Jupyter notebook widgets in PyCharm Safe Mode.

Description

A vulnerability in JetBrains PyCharm before version 2026.3 allows code execution in Safe Mode via a specially crafted Jupyter notebook widget module. This flaw enables an attacker to execute code despite Safe Mode protections.

References

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