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VulnerabilityPublished Updated

CVE-2026-44896: Jupyterlab · Mistune has XSS via unescaped figclass/figwidth in Figure directive

Affects jupyterlabSource GCVE Database

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Authoritative record:CVE-2026-44896· Medium 5.3

Not known to be exploited · CVSS 5.3 Medium : upgrade to 4.5.7_1 when convenient.

Data as of 30 Oct 2026, 09:14 UTC

CVSS 4.0 base score
5.3Medium
How severe the flaw is on the 0–10 CVSS scale.
Patch
Available – fixed in 4.5.7_1
CVSS:4.0/AV:N/AC:L/AT:N/PR:N/UI:P/VC:N/VI:N/VA:N/SC:L/SI:L/SA:N

Exploitation evidence

  1. Disclosed: evidence found.

    CVE published 26 May 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 29 Oct 2026.

What to do

Upgrade jupyterlab to 4.5.7_1.

Affected software

ProductAffectedFixed in
Homebrewjupyterlabpkg:brew/jupyterlabOther threatsAffected
  • >=1.2.0 <4.5.7_1
Fixed in
  • 4.5.7_1

Check your own hosts for these packages with threat-finder (opens in a new tab), our free open-source scanner.

AI-suggested

A patch is available in JupyterLab version 4.5.7_1 that fixes this vulnerability by properly escaping the figclass and figwidth options in the render_figure() function. Users should upgrade to version 4.5.7_1 or later to remediate this issue. No other mitigations are specified or required.

Description

CVE-2026-44896 is a cross-site scripting (XSS) vulnerability in JupyterLab's Mistune markdown renderer. The flaw occurs because the render_figure() function in src/mistune/directives/image.py inserts figclass and figwidth options directly into HTML attributes without escaping, allowing attribute injection. This bypasses the usual HTML escaping protections even when HTMLRenderer(escape=True) is used. Other attributes like src, alt, and style are properly escaped. The vulnerability affects JupyterLab versions from 1.2.0 up to but not including 4.5.7_1.

References

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