CVE-2026-49866: libp2p: CPU DoS via oversized IHAVE and IWANT control message arrays

Severity: high (CVSS 7.5 v3.1)
Exploited in the wild: not listed in CISA KEV
EPSS: 0.6% probability of exploitation in the next 30 days
Public exploit or detection template: none known
Published: 2026-07-08 · updated 2026-10-25
Weakness: CWE-770

Description

libp2p is a JavaScript Implementation of libp2p networking stack. Prior to 16.0.0, @libp2p/gossipsub defaultDecodeRpcLimits set maxIhaveMessageIDs and maxIwantMessageIDs to Infinity, allowing oversized IHAVE and IWANT control message arrays in message/decodeRpc.ts and gossipsub.ts to synchronously iterate roughly 180,000 message IDs per 4 MB frame and block the Node.js event loop. This issue is fixed in version 16.0.0.

Affected products

libp2p js-libp2p: before 16.0.0

References

https://github.com/libp2p/js-libp2p/commit/773dd80ded24dbd6b19e675c89fd2f3b45f2d899
https://github.com/libp2p/js-libp2p/pull/3520
https://github.com/libp2p/js-libp2p/releases/tag/gossipsub-v16.0.0
https://github.com/libp2p/js-libp2p/security/advisories/GHSA-cwc9-cp4j-mcvv

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