# CVE-2026-55663: mediasoup: SCTP state cookie lacks cryptographic authentication, enabling unauthorized association establishment (RFC 9260 violation)

> An on-path attacker can forge SCTP state cookies to establish unauthorized associations and inject DataChannel messages in mediasoup when DTLS is disabled.

- **Severity:** Medium 5.6 (`CVSS:3.1/AV:N/AC:H/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:** 25 Aug 2026
- **Updated:** 25 Aug 2026
- **Also known as:** GHSA-p7x2-g5cq-fhmq

## What is CVE-2026-55663?

CVE-2026-55663 is a medium-severity vulnerability in versatica mediasoup, published on 25 Aug 2026. An attacker can exploit it over the internet without logging in, with no action from the victim.

### Official description

mediasoup is a WebRTC video conferencing system. From version 3.20.0 until 3.20.6 for the npm package and from 0.22.0 until 0.22.5 for the Rust crate, mediasoup's built-in SCTP stack authenticates state cookies using only the hardcoded msworker and 0xAD81 magic values instead of a per-instance secret and HMAC, contrary to RFC 9260 Section 5.1.3. The cookie structure and validation in worker/include/RTC/SCTP/association/StateCookie.hpp and worker/src/RTC/SCTP/association/StateCookie.cpp allow an on-path attacker targeting PlainTransport or PipeTransport with SCTP enabled and without DTLS protection to forge a COOKIE-ECHO whose packet verification tag matches the attacker-controlled localVerificationTag. The forged cookie passes StateCookie::IsMediasoupStateCookie() and Association::HandleReceivedCookieEchoChunk(), establishes an unauthorized SCTP association, and permits DataChannel message injection as a trusted peer. WebRtcTransport is not affected because its SCTP runs inside DTLS. This issue is fixed in npm version 3.20.6 and Rust crate version 0.22.5.

Weakness: CWE-345 (Insufficient Verification of Data Authenticity)

## Which versions are affected by CVE-2026-55663?

4 open source packages ship an affected version, including mediasoup.


| Package | Ecosystem | Affected | Fixed in |
| --- | --- | --- | --- |
| `mediasoup` | crates.io | From 0.22.0 | 0.22.5 |
| `mediasoup` | crates.io | From 0.22.0 | 0.22.5 |
| `mediasoup` | npm | From 3.20.0 | 3.20.6 |
| `mediasoup` | npm | From 3.20.0 | 3.20.6 |

## How do I fix CVE-2026-55663?

Upgrade mediasoup to a fixed version for your release line: 0.22.5 or 3.20.6.

## Is CVE-2026-55663 being exploited?

It is not confirmed as exploited in the wild, but public exploit code for CVE-2026-55663 exists.

## Fix prompt for AI coding agents

```text
Check this codebase for CVE-2026-55663 and fix it if it is affected.

What it is: CVE-2026-55663 is a medium-severity vulnerability in versatica mediasoup, published on 25 Aug 2026. An attacker can exploit it over the internet without logging in, with no action from the victim.
Exploitation: It is not confirmed as exploited in the wild, but public exploit code for CVE-2026-55663 exists.

Affected packages and fixed versions:
- mediasoup (crates.io): affected from 0.22.0; fixed in 0.22.5
- mediasoup (crates.io): affected from 0.22.0; fixed in 0.22.5
- mediasoup (npm): affected from 3.20.0; fixed in 3.20.6
- mediasoup (npm): affected from 3.20.0; fixed in 3.20.6

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-2026-55663/ (Markdown: https://insights.sbomify.com/CVE-2026-55663/index.md)
```

## Sources

- CVE record: https://www.cve.org/CVERecord?id=CVE-2026-55663
- NVD: https://nvd.nist.gov/vuln/detail/CVE-2026-55663
- OSV: https://osv.dev/vulnerability/CVE-2026-55663

---
From sbomify Insights: https://insights.sbomify.com/CVE-2026-55663/
Summaries are generated and may contain mistakes; the official description above is the record.