# CVE-2026-28799: PJSIP: Heap use-after-free in PJSIP presence subscription termination handler

> A heap use-after-free in PJSIP's presence subscription handler allows attackers to potentially execute code or cause denial of service via crafted unsubscription requests.

- **Severity:** High 8.7 (`CVSS:4.0/AV:N/AC:L/AT:N/PR:N/UI:N/VC:N/VI:N/VA:H/SC:N/SI:N/SA:N`)
- **Exploited in the wild:** Not known
- **Login needed:** Not needed
- **Attackable:** Over the internet
- **Victim action needed:** Not needed
- **Fix available:** Yes
- **Published:** 6 Mar 2026
- **Updated:** 9 Mar 2026
- **Also known as:** ALPINE-CVE-2026-28799, DEBIAN-CVE-2026-28799, GHSA-8fj4-fv9f-hjpc, UBUNTU-CVE-2026-28799

## What is CVE-2026-28799?

CVE-2026-28799 is a high-severity use after free vulnerability in pjsip pjproject, published on 6 Mar 2026. 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. Prior to version 2.17, a heap use-after-free vulnerability exists in PJSIP's event subscription framework (evsub.c) that is triggered during presence unsubscription (SUBSCRIBE with Expires=0). This issue has been patched in version 2.17.

Weakness: CWE-416 (Use After Free)

## Which versions are affected by CVE-2026-28799?

It affects 1 product.


Products: Pjsip Pjsip.

## How do I fix CVE-2026-28799?

Upgrade to a fixed version.

## Is CVE-2026-28799 being exploited?

There is no known exploitation of CVE-2026-28799 in the wild and no public exploit code.

## Other vulnerabilities in pjsip pjproject

- [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)
- [CVE-2026-26967](https://insights.sbomify.com/CVE-2026-26967/): PJSIP has a Heap-based Buffer Overflow vulnerability in its H.264 unpacketizer (high 8.1)

## Fix prompt for AI coding agents

```text
Check this codebase for CVE-2026-28799 and fix it if it is affected.

What it is: CVE-2026-28799 is a high-severity use after free vulnerability in pjsip pjproject, published on 6 Mar 2026. 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-2026-28799 in the wild and no public exploit code.

Affected product: pjsip pjproject. 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-2026-28799/ (Markdown: https://insights.sbomify.com/CVE-2026-28799/index.md)
```

## Sources

- CVE record: https://www.cve.org/CVERecord?id=CVE-2026-28799
- NVD: https://nvd.nist.gov/vuln/detail/CVE-2026-28799
- OSV: https://osv.dev/vulnerability/CVE-2026-28799

---
From sbomify Insights: https://insights.sbomify.com/CVE-2026-28799/
Summaries are generated and may contain mistakes; the official description above is the record.