# CVE-2026-34063: network-libp2p: Peer can crash the node by opening discovery protocol substream twice


- **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
- **Fix available:** No
- **Published:** 22 Apr 2026
- **Updated:** 23 Apr 2026
- **Also known as:** GHSA-74hp-mhfx-m45h

## What is CVE-2026-34063?

CVE-2026-34063 is a high-severity vulnerability in nimiq network-libp2p, published on 22 Apr 2026. 

### Official description

Nimiq's network-libp2p is a Nimiq network implementation based on libp2p. Prior to version 1.3.0, `network-libp2p` discovery uses a libp2p `ConnectionHandler` state machine. the handler assumes there is at most one inbound and one outbound discovery substream per connection. if a remote peer opens/negotiate the discovery protocol substream a second time on the same connection, the handler hits a `panic!(\"Inbound already connected\")` / `panic!(\"Outbound already connected\")` path instead of failing closed. This causes a remote crash of the networking task (swarm), taking the node's p2p networking offline until restart. The patch for this vulnerability is formally released as part of v1.3.0. No known workarounds are available.

Weakness: CWE-617 (Reachable Assertion)

## Which versions are affected by CVE-2026-34063?

It affects 1 product.


Products: Nimiq Nimiq Proof-of-Stake.

## How do I fix CVE-2026-34063?

No fix has been published for CVE-2026-34063 yet. Limit exposure of the affected software until one is available.

## Is CVE-2026-34063 being exploited?

There is no known exploitation of CVE-2026-34063 in the wild and no public exploit code.

## Other vulnerabilities in nimiq network-libp2p

- [CVE-2026-33471](https://insights.sbomify.com/CVE-2026-33471/): nimiq-block has skip block quorum bypass via out-of-range BitSet indices & u16 truncation (critical 9.6)
- [CVE-2026-40093](https://insights.sbomify.com/CVE-2026-40093/): nimiq-blockchain is missing a wall-clock upper bound on block timestamps (high 8.1)
- [CVE-2026-34065](https://insights.sbomify.com/CVE-2026-34065/): nimiq-primitives: Node crash due to missing interlink validation in election macro block proposals (high 7.5)
- [CVE-2026-32605](https://insights.sbomify.com/CVE-2026-32605/): Nimiq: Remote crash via off-by-one signer bounds check in proposal buffer (high 7.5)
- [CVE-2026-33184](https://insights.sbomify.com/CVE-2026-33184/): nimiq/core-rs-albatross: Discovery handshake limit could underflow and later provoke a deterministic overflow panic (high 7.5)

## Fix prompt for AI coding agents

```text
Check this codebase for CVE-2026-34063 and fix it if it is affected.

What it is: CVE-2026-34063 is a high-severity vulnerability in nimiq network-libp2p, published on 22 Apr 2026. 
Exploitation: There is no known exploitation of CVE-2026-34063 in the wild and no public exploit code.

Affected product: nimiq network-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-2026-34063/ (Markdown: https://insights.sbomify.com/CVE-2026-34063/index.md)
```

## Sources

- CVE record: https://www.cve.org/CVERecord?id=CVE-2026-34063
- NVD: https://nvd.nist.gov/vuln/detail/CVE-2026-34063
- OSV: https://osv.dev/vulnerability/CVE-2026-34063

---
From sbomify Insights: https://insights.sbomify.com/CVE-2026-34063/
Summaries are generated and may contain mistakes; the official description above is the record.