High severity · published Jul 8, 2026
CVE-2026-49866
libp2p: CPU DoS via oversized IHAVE and IWANT control message arrays
7.5
CVSS
0.6%
EPSS
No
On KEV
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.
CVSS vector
CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:N/I:N/A:H
Attack vector
Network
Complexity
Low
Privileges
None
User interaction
None
Confidentiality
None
Integrity
None
Availability
High
Scope
Unchanged
Exploitation
Is it being used?
Exploit prediction (EPSS)0.6% · higher than 50% of CVEs
Exploited in the wildNo evidence yet
CISA KEVNot listed
Ransomware campaign useNot known
Affected products
Which versions
JS
js-libp2p · libp2p
< 16.0.0 · source: vendor
References
NVD
https://nvd.nist.gov/vuln/detail/CVE-2026-49866
CVE.org
https://www.cve.org/CVERecord?id=CVE-2026-49866
github.com
https://github.com/libp2p/js-libp2p/commit/773dd80ded24dbd6b19e675c89fd2f3b45f2d899
github.com
https://github.com/libp2p/js-libp2p/pull/3520
github.com
https://github.com/libp2p/js-libp2p/releases/tag/gossipsub-v16.0.0
github.com
https://github.com/libp2p/js-libp2p/security/advisories/GHSA-cwc9-cp4j-mcvv
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