CVE-2026-77384 libp2p CVE debrief

Who should care

Defenders of libp2p implementations, particularly those using @libp2p/circuit-relay-v2 relay servers, should assess exposure and verify if their implementation is prior to version 4.2.9.

Why it matters

Defenders should prioritize verifying if their libp2p implementation is prior to version 4.2.9 and apply the patch or upgrade to mitigate potential denial-of-service attacks. The vulnerability allows remote peers to cause unbounded listener and closure growth in @libp2p/circuit-relay-v2 relay servers.

• Denial-of-service attacks due to unbounded listener and closure growth
• Potential for remote peers to repeatedly send valid RESERVE requests for the same reservation

Technical summary

The reservation refresh path in reservation-store.ts reuses the same retimeableSignal but unconditionally registers another abort listener on every refresh, allowing a remote peer to repeatedly send valid RESERVE requests for the same reservation and cause unbounded listener and closure growth in @libp2p/circuit-relay-v2 relay servers. This issue can lead to denial-of-service attacks and defenders should prioritize verifying if their libp2p implementation is prior to version 4.2.9 and apply the patch or upgrade to mitigate potential attacks.

Defensive priority

Defenders should prioritize verifying if their libp2p implementation is prior to version 4.2.9 and apply the patch or upgrade to mitigate potential denial-of-service attacks.

Recommended defensive actions

• Verify if the libp2p implementation is prior to version 4.2.9
• Apply the patch or upgrade to version 4.2.9 or later
• Monitor for potential denial-of-service attacks
• Review compensating controls for exposed systems while remediation is scheduled and verified
• Check relevant monitoring, detection, and logs for exposed assets that need extra review
• Track exceptions, retest remediated assets, and close the item only after evidence is documented
• Confirm whether affected product deployments exist in managed environments and assign an owner for follow-up

Evidence notes

The CVE record and NVD entry provide details on the vulnerability in libp2p versions prior to 4.2.9, which could lead to denial-of-service attacks due to unbounded listener and closure growth. Defenders should verify if their implementation is prior to version 4.2.9 and review the official advisory for affected scope and severity. Evidence is limited to public CVE details and NVD assessments.

Sources and references

Methodology and review provenance

AI-assisted synthesis based on stored public vulnerability evidence. System validation, approval state, and publication status do not by themselves establish human review of this revision. PatchSiren helps prioritize defensive review and does not prove exposure or remediation on any system.