# CVE-2026-103936: libp2p: Single pre-auth STUN packet terminates `@libp2p/webrtc` WebRTC-direct Node.js listeners

> A remote attacker can crash the libp2p WebRTC listener by sending a single malformed STUN packet, causing a denial of service.

- **Severity:** High 7.5 (`CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:N/I:N/A:H`)
- **Exploited in the wild:** Not known
- **Login needed:** Not needed
- **Attackable:** Over the internet
- **Victim action needed:** Not needed
- **Fix available:** No
- **Published:** 15 Oct 2026
- **Updated:** 16 Oct 2026
- **Also known as:** GHSA-x3m2-6mg8-vj7f

## What is CVE-2026-103936?

CVE-2026-103936 is a high-severity denial of service vulnerability in @libp2p js-libp2p, published on 15 Oct 2026. An attacker can exploit it over the internet without logging in, with no action from the victim.

### Official description

libp2p is a JavaScript implementation of the libp2p networking stack. Prior to 6.0.28, the @libp2p/webrtc webRTCDirect() Node.js listener processes unauthenticated STUN Binding Requests before PeerId authentication, Noise, muxing, protocol negotiation, connection creation, or connection-manager admission. The listener in packages/transport-webrtc/src/private-to-public/utils/stun-listener.ts forwards the packet-controlled request.ufrag into DirectRTCPeerConnection.setLocalDescription, where the value is reused as an ICE password without validating its required length and character set. A short credential causes node-datachannel or libdatachannel to raise an uncaught native invalid_argument and abort the process with SIGABRT, allowing a single remote UDP packet to deny service. The confirmed impact is process termination only, with no demonstrated memory corruption, code execution, browser impact, confidentiality impact, integrity impact, or connection-limit bypass. This issue is fixed in version 6.0.28.

Weakness: CWE-755 (Improper Handling of Exceptional Conditions), CWE-248 (Uncaught Exception)

## Which versions are affected by CVE-2026-103936?


## How do I fix CVE-2026-103936?

No fix has been published for CVE-2026-103936 yet. Limit exposure of the affected software until one is available.

## Is CVE-2026-103936 being exploited?

There is no known exploitation of CVE-2026-103936 in the wild and no public exploit code.

## Fix prompt for AI coding agents

```text
Check this codebase for CVE-2026-103936 and fix it if it is affected.

What it is: CVE-2026-103936 is a high-severity denial of service vulnerability in @libp2p js-libp2p, published on 15 Oct 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-2026-103936 in the wild and no public exploit code.

Affected product: @libp2p js-libp2p. 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-2026-103936/ (Markdown: https://insights.sbomify.com/CVE-2026-103936/index.md)
```

## Sources

- CVE record: https://www.cve.org/CVERecord?id=CVE-2026-103936
- NVD: https://nvd.nist.gov/vuln/detail/CVE-2026-103936
- OSV: https://osv.dev/vulnerability/CVE-2026-103936

---
From sbomify Insights: https://insights.sbomify.com/CVE-2026-103936/
Summaries are generated and may contain mistakes; the official description above is the record.