CVE-2026-33151

socket.io allows an unbounded number of binary attachments

CVSS 4.0 8.7 HIGHEUVD CVSS 4.0 8.7 CVSS 4.0 · [email protected] · Secondary 8.7 HIGHCVSS 3.1 · [email protected] · Primary 7.5 HIGHCVSS_V4 Publisher rating HIGHFixed by socket.io-parser 3.3.5 Fixed by socket.io-parser 3.4.4 Fixed by socket.io-parser 4.2.6KEV status unknown

Original advisory

cve-program · CVE-2026-33151

Published

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.

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euvd · EUVD-2026-13788

Published

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nvd · CVE-2026-33151

Published

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osv · GHSA-677m-j7p3-52f9

Published

### 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` | `[email protected]` and `[email protected]` | `4.2.6` | | `>=3.4.0 <3.4.4` | `[email protected]` | `3.4.4` | | `<3.3.5` | `[email protected]` | `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)

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Affected versions, risk and source history

Exploitation and risk

Source status

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Risk history

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Advisory history

13 saved versions

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15 Nov 2026 09:37:41 UTC