Socket.IO: Zero-attachment Memory Exhaustion

### 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 <4.2.7` | `[email protected]` and `[email protected]` | `4.2.7` | | `>=3.4.0 <3.4.5` | `[email protected]` | `3.4.5` | | `<3.3.6` | `[email protected]` | `3.3.6` | ### 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)

Source published

3 Aug 2026 19:09:44 UTC

Source modified

10 Sep 2026 03:50:53 UTC

Observed here

24 Oct 2026 13:17:17 UTC

Source terms

GitHub Advisory Database · CC-BY-4.0

Original source record · Cite this exact observation · Complete original publisher JSON

This view projects the publisher's source fields for reading; the original JSON retains additional fields and CVE enrichment containers. Attribution: osv · GitHub Advisory Database · CC-BY-4.0. Source text is retained; field grouping and change labels are provided by ChangeIntel.

CVSS_V3 · CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:N/I:N/A:H

Publisher rating · HIGH