High 8.7Published Mar 20, 2026

CVE-2026-33151socket.io allows an unbounded number of binary attachments

Updated under an hour ago (Oct 26, 2026, 3:40 AM ET)

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It affects socketio socket.io and 1 other product. Add what you run to find out whether that includes you.

No exploitation reported and no EPSS estimate yet.

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Every CVE for socketio socket.io

Exploited in the last 30 days

Socket.IO is an open source, real-time, bidirectional, event-based, communication framework. Prior to versions 3.3.5, 3.4.4, and 4.2.6, a specially crafted Socket.IO packet can make the server wait for a large number of binary attachments and buffer them, which can be exploited to make the server run out of memory. This issue has been patched in versions 3.3.5, 3.4.4, and 4.2.6.

CVSS: 8.7 HIGH (v4.0, CNA)CVSS:4.0/AV:N/AC:L/AT:N/PR:N/UI:N/VC:N/VI:N/VA:H/SC:N/SI:N/SA:N
Weakness (CWE): CWE-20, CWE-754
Known exploited: Not in CISA's KEV catalog
EPSS (exploitation in the next 30 days): Not loaded for this CVE
Assigned by: GitHub_M
NVD analysis: Analyzed
Record last updated: Mar 23, 2026
First seen by InfoSec Signals: Oct 9, 2026

Affected products

Affected products

socketio socket.io socketio:socket.io (from the name)	before 3.3.5; from 3.4.0, < 3.4.4; from 4.0.0, < 4.2.6	CNA record
socket socket.io-parser socket:socket.io-parser	before 3.3.5; from 3.4.0 before 3.4.4; from 4.0.0 before 4.2.6	NVD

References

https://github.com/socketio/socket.io/security/advisories/GHSA-677m-j7p3-52f9x-refsource-confirm, patch, vendor-advisory
https://github.com/socketio/socket.io/commit/719f9ebab0772ffb882bd614b387e585c1aa75d4x-refsource-misc, patch
https://github.com/socketio/socket.io/commit/9d39f1f080510f036782f2177fac701cc041faafx-refsource-misc, patch
https://github.com/socketio/socket.io/commit/b25738c416c4e32fbff62ee182afa8f6d0dacf78x-refsource-misc, patch

The CVE record on cve.org NVD's entry

The CVE record is authoritative. Products marked “from the name” were identified from the CNA's free-text names, not a CPE, and are matched less certainly. This product uses the NVD API but is not endorsed or certified by the NVD.