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CVE-2026-111059 · GHSA-2658-85cv-9wwq

Mercury: Stored / DOM Cross-Site Scripting (XSS): mr.Markdown renders untrusted content as raw, unsanitized HTML

Risk score
51/100
CVSS
6.1 v3.1
Exploit chance (30 days)
0.3%
Published
19 Oct 2026

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What to know

What it is
Mercury is a Python framework for sharing Jupyter notebooks as web applications and dashboards. From 3.0.0 until 3.2.11, mr.Markdown converts attacker-controlled Markdown to HTML without sanitizing raw HTML before assigning it to an ipywidgets.HTML sink. Event-handler attributes and other active HTML can therefore rea…
Affected
mercury (pip) >= 3.0.0, < 3.2.11
Fix
Upgrade mercury to 3.2.11 or later.
Exploitation
Public proof of concept

Story map

Story map: mercuryTHE FLAWSTHE FIXCVE-2026-111059Mercury: Stored / DOMCross-Site Scripting (XSS):mr.Markdown renders…CVSS 6.1 · EPSS 0%CVE-2026-111057Mercury: UnauthenticatedRemote Code Execution in/api/terminals - access…CVSS 10.0 · EPSS 0%CVE-2026-111058Mercury: UnauthenticatedRemote Code Execution via/api/kernelsCVSS 9.8 · EPSS 0%Upgrade mercury3.2.11 · 3.2.4 · 3.2.6or later on your release lineWho is exposed{'products': ['Mercury'],'packages': [{'ecosystem': 'pip','name': 'mercury', 'vulnerable':'>= 3.0.0, <= 3.2.3', 'patched':'3.2.4'}]}AMBER · PATCH THIS WEEKmercuryA vulnerability in Mercury allowsan unauthenticated attacker toexecute commands and accessdata through an interactiveoperating-system shell. This isdue to a missing comma in theBLOCKED_PATTERNS…Where it standsPublic proof of conceptCONNECTS TOSame weaknessCross-site scripting (CWE-79)400 other warnings in 30 days →
Story map: the flaws, the fix, how it unfolded and what it connects to. Boxes link to the record or article.

At a glance

mercury: Amber, patch this week. A vulnerability in Mercury allows an unauthenticated attacker to execute commands and access data through an interactive operating-system shell. This is due to a missing comma in the BLOCKED_PATTERNS regular-expression literals.

The flaws

  • CVE-2026-111059: Mercury: Stored / DOM Cross-Site Scripting (XSS): mr.Markdown renders untrusted content as raw, unsanitized HTML (CVSS 6.1 · EPSS 0%)
  • CVE-2026-111057: Mercury: Unauthenticated Remote Code Execution in /api/terminals - access control bypass (CVSS 10.0 · EPSS 0%)
  • CVE-2026-111058: Mercury: Unauthenticated Remote Code Execution via /api/kernels (CVSS 9.8 · EPSS 0%)

The fix

Upgrade mercury: 3.2.11 · 3.2.4 · 3.2.6 or later on your release line

Who is exposed: {'products': ['Mercury'], 'packages': [{'ecosystem': 'pip', 'name': 'mercury', 'vulnerable': '>= 3.0.0, <= 3.2.3', 'patched': '3.2.4'}]}

Where it stands

  • Public proof of concept

Connects to

Why it is Yellow

  • CVSS 6.1 medium
  • Public exploit or proof of concept referenced
  • On your watchlist: PyPI

Affected packages

PackageEcosystemVulnerableFixed in
mercurypip>= 3.0.0, < 3.2.113.2.11

References

Original description

Mercury is a Python framework for sharing Jupyter notebooks as web applications and dashboards. From 3.0.0 until 3.2.11, mr.Markdown converts attacker-controlled Markdown to HTML without sanitizing raw HTML before assigning it to an ipywidgets.HTML sink. Event-handler attributes and other active HTML can therefore reach the DOM and execute when another user views the application. This issue is fixed in version 3.2.11.

Last activity 19 Oct 2026. Patch Forecast updates every hour.