External risk intelligence

Mercury Terminal API Command Execution Vulnerability

CVE advisorySeverity: CRITICAL (CVSS 10.0)

CVE-2026-111057

Mercury is a framework specifically designed to share Jupyter notebooks as public-facing web applications and dashboards. Because the primary purpose of the software is to expose data science tools and interfaces to users over the web, the vulnerable endpoints are commonly deployed in internet-facing configurations.

Halo Surface Signal: 4 out of 5 — likely to be public-facing.

External exposure likelihood

Horizon Alert

Summary of the vulnerability and why it matters

A vulnerability in the Mercury framework could allow unauthenticated attackers to execute commands and access data by bypassing security checks on terminal access. This could potentially expose sensitive information or allow unauthorized system control.

Unauthenticated access to sensitive data.
Affects sharing Jupyter notebooks over the web.
Confirm exposure and confirm relevance.

Attack Path

How an attacker could exploit the issue

An unauthenticated attacker could exploit this vulnerability by sending requests to a Mercury-powered web application. Due to a configuration error, these requests bypass security checks intended to block access to sensitive features, specifically targeting the terminal API. This allows the attacker to gain an interactive shell on the server, potentially leading to command execution and data theft.

Unauthenticated network access required.
Requests target the terminal API endpoint.
Allows command execution and data access.

Live Threat

Current exploitation, exposure, and threat context

This vulnerability could allow an unauthenticated attacker to bypass security controls and access the terminal API, potentially leading to command execution and unauthorized data access within the Mercury process. This could occur when the affected Mercury application is configured with the specific regular expression error.

System data could be exposed.
Remote unauthenticated access can exploit.
Commands may execute with process privileges.

Operational Fix

Recommended remediation, mitigation, and detection steps

Application owners and platform teams are likely responsible for addressing this vulnerability in the Mercury framework. The first practical step is to identify all Mercury instances, determine their exposure and business criticality, and then locate the accountable owner for remediation planning.

Identify Mercury instances and owners.
Verify external reachability and impact.
Plan remediation based on risk.

Supplementary metadata

CVSS vector

Validate whether this threat affects your internet-facing exposure.

Halo Threat Intelligence helps prioritize remediation with Halo Surface Signal and H/A/L/O context. Start exposure validation with a free external attack surface trial.

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Frequently asked questions

What is Mercury and why do people use it?

Mercury is a Python-based framework designed to convert Jupyter notebooks into interactive web applications and dashboards. Data scientists and developers use it to share analytical models and data visualizations with broader audiences, allowing users to interact with notebooks through a web interface without needing to run the full Jupyter environment themselves.

What does CWE-185/CWE-284 mean for CVE-2026-111057?

This vulnerability is a configuration error categorized as an Improper Validation of Regular Expression (CWE-185) leading to Improper Access Control (CWE-284). Essentially, a missing comma in the application's configuration causes it to incorrectly merge security patterns. This mistake accidentally disables the intended restrictions that prevent unauthorized users from accessing the underlying terminal system.

How does an attacker trigger this vulnerability?

An attacker triggers this by sending specific network requests to the Mercury web application that target the terminal API endpoint. Because the application's security filter was misconfigured, it fails to recognize these requests as forbidden. Note that this does not require any specialized credentials; simple web requests to the path that should be blocked are enough to bypass the check.

Is my Mercury deployment relevant to this risk?

According to Halo Surface Signal, this vulnerability is particularly relevant to Mercury instances because the framework's primary function is to share content via public-facing dashboards. If your instance is reachable from the internet, it is inherently exposed to these unauthorized requests, making it a priority for review compared to strictly internal, isolated tools.

What steps should I take if I run Mercury?

Your first step is to identify all running instances of Mercury within your infrastructure and confirm their version numbers. If you are running any version from 3.0.0 up to, but not including, 3.2.4, you are affected. You should prioritize updating to version 3.2.4 or later, as this release contains the configuration fix that correctly restricts access to the terminal API.

References

Written by Nicholas Merritt

Nicholas Merritt is VP of Security Solutions at Halo Security. With more than 25 years across application security, vulnerability prioritization, and offensive security, he helps teams translate threat data into practical exposure validation and remediation focus. He authors Halo Threat Intelligence CVE advisories using Halo Surface Signal and H/A/L/O context to prioritize internet-facing risk.