# CVE-2026-26203: PJSIP's pjmedia-video has use-after-free in H264 packetizer when packetizing fragmented NAL

> Attackers can trigger a heap buffer underflow in PJSIP's H.264 packetizer via malformed bitstreams, potentially leading to code execution or crashes.

- **Severity:** Medium 5.1 (`CVSS:4.0/AV:L/AC:L/AT:N/PR:N/UI:N/VC:N/VI:N/VA:N/SC:N/SI:N/SA:L`)
- **Exploited in the wild:** Not known
- **Login needed:** Not needed
- **Attackable:** Local or same network only
- **Victim action needed:** Not needed
- **Fix available:** Yes
- **Published:** 19 Feb 2026
- **Updated:** 19 Feb 2026
- **Also known as:** ALPINE-CVE-2026-26203, DEBIAN-CVE-2026-26203, GHSA-p965-mf7j-gwv8, UBUNTU-CVE-2026-26203

## What is CVE-2026-26203?

CVE-2026-26203 is a medium-severity use after free vulnerability in pjsip pjmedia-video, published on 19 Feb 2026. It can only be exploited from the same machine or local network, with no action from the victim.

### Official description

PJSIP is a free and open source multimedia communication library. Versions prior to 2.17 have a critical heap buffer underflow vulnerability in PJSIP's H.264 packetizer. The bug occurs when processing malformed H.264 bitstreams without NAL unit start codes, where the packetizer performs unchecked pointer arithmetic that can read from memory located before the allocated buffer. Version 2.17 contains a patch for the issue.

Weakness: CWE-416 (Use After Free)

## Which versions are affected by CVE-2026-26203?

It affects 1 product.


Products: Pjsip Pjsip.

## How do I fix CVE-2026-26203?

Upgrade to a fixed version.

## Is CVE-2026-26203 being exploited?

There is no known exploitation of CVE-2026-26203 in the wild and no public exploit code.

## Other vulnerabilities in pjsip pjmedia-video

- [CVE-2026-28799](https://insights.sbomify.com/CVE-2026-28799/): PJSIP: Heap use-after-free in PJSIP presence subscription termination handler (high 8.7)
- [CVE-2026-29068](https://insights.sbomify.com/CVE-2026-29068/): PJSIP: Stack buffer overflow in Opus codec parser (high 8.7)
- [CVE-2026-40614](https://insights.sbomify.com/CVE-2026-40614/): PJSIP: Heap buffer overflow in Opus codec decoding (high 8.5)
- [CVE-2026-32945](https://insights.sbomify.com/CVE-2026-32945/): PJSIP is vulnerable to Heap-based Buffer Overflow through DNS parser (high 8.4)
- [CVE-2026-40892](https://insights.sbomify.com/CVE-2026-40892/): PJSIP: Stack buffer overflow in pjsip_auth_create_digest2() (high 8.1)

## Fix prompt for AI coding agents

```text
Check this codebase for CVE-2026-26203 and fix it if it is affected.

What it is: CVE-2026-26203 is a medium-severity use after free vulnerability in pjsip pjmedia-video, published on 19 Feb 2026. It can only be exploited from the same machine or local network, with no action from the victim.
Exploitation: There is no known exploitation of CVE-2026-26203 in the wild and no public exploit code.

Affected product: pjsip pjmedia-video. 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-2026-26203/ (Markdown: https://insights.sbomify.com/CVE-2026-26203/index.md)
```

## Sources

- CVE record: https://www.cve.org/CVERecord?id=CVE-2026-26203
- NVD: https://nvd.nist.gov/vuln/detail/CVE-2026-26203
- OSV: https://osv.dev/vulnerability/CVE-2026-26203

---
From sbomify Insights: https://insights.sbomify.com/CVE-2026-26203/
Summaries are generated and may contain mistakes; the official description above is the record.