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

> A malicious actor can trigger an out-of-bounds read in PJSIP by sending a crafted RTCP BYE message, potentially causing crashes or data exposure.

- **Severity:** High 7.3 (`CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:L/I:L/A:L`)
- **Exploited in the wild:** Not known
- **Login needed:** Not needed
- **Attackable:** Over the internet
- **Victim action needed:** Not needed
- **Fix available:** Yes
- **Published:** 22 Dec 2021
- **Updated:** 4 Nov 2025
- **Also known as:** ALPINE-CVE-2021-43804, DEBIAN-CVE-2021-43804, GHSA-3qx3-cg72-wrh9, UBUNTU-CVE-2021-43804

## What is CVE-2021-43804?

CVE-2021-43804 is a high-severity memory corruption vulnerability in Debian Debian Linux, published on 22 Dec 2021. An attacker can exploit it over the internet without logging in, with no action from the victim.

### Official 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.

Weakness: CWE-125 (Out-of-bounds Read)

## Which versions are affected by CVE-2021-43804?

It affects 2 products.


Products: Debian Debian Linux, Teluu Pjsip.

## How do I fix CVE-2021-43804?

Upgrade to a fixed version.

## Is CVE-2021-43804 being exploited?

There is no known exploitation of CVE-2021-43804 in the wild and no public exploit code.

## Other vulnerabilities in Debian Debian Linux

- [CVE-2015-3306](https://insights.sbomify.com/CVE-2015-3306/): ProFTPD Improper Access Control (critical 10.0, exploited in the wild)
- [CVE-2025-49113](https://insights.sbomify.com/CVE-2025-49113/): RoundCube Webmail Deserialization of Untrusted Data (critical 9.9, exploited in the wild)
- [CVE-2026-24061](https://insights.sbomify.com/CVE-2026-24061/): GNU InetUtils Argument Injection (critical 9.8, exploited in the wild)
- [CVE-2025-39682](https://insights.sbomify.com/CVE-2025-39682/): Linux Kernel Improper Check for Unusual or Exceptional Conditions (critical 9.8, exploited in the wild)
- [CVE-2024-9680](https://insights.sbomify.com/CVE-2024-9680/): Mozilla Firefox Use-After-Free (critical 9.8, exploited in the wild)

## Fix prompt for AI coding agents

```text
Check this codebase for CVE-2021-43804 and fix it if it is affected.

What it is: CVE-2021-43804 is a high-severity memory corruption vulnerability in Debian Debian Linux, published on 22 Dec 2021. An attacker can exploit it over the internet without logging in, with no action from the victim.
Exploitation: There is no known exploitation of CVE-2021-43804 in the wild and no public exploit code.

Affected product: Debian Debian Linux. No package-level version data is available, so check the vendor advisory linked from the reference page.

Task:
1. Search the dependency manifests and lockfiles (for example package.json, package-lock.json, requirements.txt, poetry.lock, uv.lock, pom.xml, build.gradle, go.mod, Cargo.lock, Gemfile.lock) and any Dockerfiles for the affected packages, including transitive dependencies.
2. If an affected version is in use, upgrade it to the fixed version for its release line with the project's package manager, so the lockfile is regenerated. Prefer the smallest upgrade that fixes it.
3. If there is no fix, or the upgrade would break the build, do not guess: explain the risk and the safest workaround instead.
4. Run the tests and summarise what changed and why.
5. If nothing in the project is affected, say so and change nothing.

Reference: https://insights.sbomify.com/CVE-2021-43804/ (Markdown: https://insights.sbomify.com/CVE-2021-43804/index.md)
```

## Sources

- CVE record: https://www.cve.org/CVERecord?id=CVE-2021-43804
- NVD: https://nvd.nist.gov/vuln/detail/CVE-2021-43804
- OSV: https://osv.dev/vulnerability/CVE-2021-43804

---
From sbomify Insights: https://insights.sbomify.com/CVE-2021-43804/
Summaries are generated and may contain mistakes; the official description above is the record.