CVE-2026-111058: Mercury Unauthenticated Remote Code Execution via /api/kernels
Summary
CVE-2026-111058: Mercury: Unauthenticated Remote Code Execution via /api/kernels. Affects mercury versions < 3.2.6. Fixed in 3.2.6. How to fix ↓
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Background
Mercury is a JupyterLab server designed for running notebooks with ease of use and accessibility. It supports anonymous access by default, allowing users to interact with the server without authentication. However, this default configuration poses significant security risks, particularly through unauthenticated access to critical endpoints.
Vulnerability Detail
The vulnerability arises from Mercury's default configuration, which allows anonymous access without proper authentication. Specifically, the /api/kernels endpoint is not included in the blocklist that restricts access to sensitive operations. This oversight enables unauthenticated users to create kernels and execute arbitrary Python code remotely, leading to complete compromise of the server. The vulnerability is exacerbated by the lack of filtering in the execute_request handler, allowing any network client to send malicious commands.
How To Fix
Latest published version: 3.2.11 as of 22 Oct 2026
pip install --upgrade "mercury==3.2.11"Upgrading to it may include breaking changes; the version below is the minimum fixed release for this vulnerability.
If you need the minimum change
3.2.6
This is the first release that contains the fix.
pip install --upgrade "mercury==3.2.6"Tip — Not sure which version your app runs? Vulert can match this fix to it. Scan free →
Workaround
As a temporary workaround, consider disabling anonymous access by configuring the server to require a token or password for all requests. This can be done by setting the MERCURY_TOKEN environment variable or using the --token option when starting the server.
Conclusion
The vulnerability identified as CVE-2026-111058 in the Mercury package allows unauthenticated remote code execution through the /api/kernels endpoint. It is crucial to update to the patched version 3.2.6 or later and implement authentication measures to secure the server against potential attacks.
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FAQ
The vulnerability allows unauthenticated remote code execution, enabling attackers to run arbitrary code on the server, potentially compromising sensitive data and system integrity.
You can use Vulert's playground at Vulert Scanner to check if your application is affected by this vulnerability without needing to sign up.
The CVSS score for this vulnerability is 9.8, indicating a critical level of severity.
Yes, you can temporarily secure your Mercury server by disabling anonymous access and requiring authentication for all requests.
If an immediate upgrade is not possible, implement the workaround by requiring authentication for all requests to minimize the risk of exploitation.
References
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