socket.io allows an unbounded number of binary attachments
### Impact 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. ### Patches | Version range | Used by | Fixed version | |------------------|--------------------------------------------|---------------| | `>=4.0.0 <4.2.6` | `socket.io@4.x` and `socket.io-client@4.x` | `4.2.6` | | `>=3.4.0 <3.4.4` | `socket.io@2.x` | `3.4.4` | | `<3.3.5` | `socket.io-client@2.x` | `3.3.5` | ### Workarounds There is no known workaround except upgrading to a safe version. ### For more information If you have any questions or comments about this advisory: - Open a discussion [here](https://github.com/socketio/socket.io/discussions)
describes (1)
Related CVEs.
| ID | severity | exploitable |
|---|---|---|
| CVE-2026-33151US | high | — |
references
External citations — patches, advisories, analysis.
- https://github.com/socketio/socket.ioPACKAGE
- https://github.com/socketio/socket.io/commit/719f9ebab0772ffb882bd614b387e585c1aa75d4WEB
- https://github.com/socketio/socket.io/commit/9d39f1f080510f036782f2177fac701cc041faafWEB
- https://github.com/socketio/socket.io/commit/b25738c416c4e32fbff62ee182afa8f6d0dacf78WEB
- https://github.com/socketio/socket.io/security/advisories/GHSA-677m-j7p3-52f9WEB
- https://nvd.nist.gov/vuln/detail/CVE-2026-33151ADVISORY
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