Quick answers
- Is CVE-2026-54566 exploited in the wild?
- No. Junglewise Threat Intelligence has no report of CVE-2026-54566 being exploited in the wild.
- How severe is CVE-2026-54566?
- Informational severity, published 14 October 2026.
- Which products and versions are affected?
- Shd101wyy Markdown Preview Enhanced before 0.8.29.
- Is there a fix for CVE-2026-54566?
- Yes: fixed in 0.8.29. Junglewise finds every place you run it, drafts the upgrade and applies it once you approve.
- How is CVE-2026-54566 attacked?
- It is attacked over the network, in a software library.
- Am I affected by CVE-2026-54566?
- Check whether you run Shd101wyy Markdown Preview Enhanced at an affected version. Junglewise does that check for you around the clock: connect your code, cloud and domains, and it matches new vulnerabilities like this one against what you actually run and tells you when one reaches you.
How to fix
- Fixed in: 0.8.29
Technical details
The vulnerability exists in the evaluation of .crossnote/config.js and .crossnote/parser.js files using vm.runInNewContext() and sval, neither of which provides a security boundary from the Node.js host realm. Attackers can use prototype-chain traversal via ({}).constructor.constructor to reach the host Function constructor and access the process object, achieving remote code execution simply by a user opening a Markdown file in a malicious repository. The fix isolates these files in a QuickJS WebAssembly sandbox with separate realm and intrinsics, preventing access to host globals and process.
Affected products
- shd101wyy Markdown Preview Enhanced before 0.8.29
Timeline
- 2026-10-14: disclosed
- 2026-06-06: patched: Fix released in version 0.9.30 with QuickJS WebAssembly sandbox