python-socketio: Binary attachment accumulation can cause denial of service
Impact
The python-socketio server stores binary EVENT and ACK messages in memory while it waits to receive their binary attachments. Once all the attachments are received, these messages are then processed. An attacker can submit a binary message and intentionally omit sending one or more of its attachments to cause the message along with the partial list of received attachments to stay in memory for a long time.
Patches
Version 5.16.2 takes the following measures to address this issue:
- Binary packets are only accepted from authenticated clients.
- When a client disconnects, the server checks if there is a partial binary message being held for the client and deletes it.
Affected software
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| Platform | Package | Vulnerable versions | Fixed in |
|---|---|---|---|
| Python (PyPI) | python-socketio | < 5.16.2 | 5.16.2 |
References
- CVSS vector
CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:N/I:N/A:H- Weakness (CWE)
CWE-770- Platform
- Python (PyPI)
- Package
python-socketio- Disclosed
- 26.06.2026
- Updated
- 11.10.2026 14:18
Sources and licenses
OSV / GitHub Advisory Database - PYSEC-2026-3042 - PyPA Advisory Database; CC BY 4.0
OSV / GitHub Advisory Database - GHSA-5w7q-77mv-v69f - CC BY 4.0
Vulnerability history: python-socketio
All published vulnerabilities of this package (Python (PyPI)), newest first. Shows whether this is a one-off slip or a package that needs watching.
- Total entries
- 2
- First → latest
- 10.2025 06.2026
- Without a fix
- 0
- Exploited in attacks
- 0
Severity breakdown
- High 1
- Medium 1
Disclosures per year
- 2025: 1
- 2026: 1
-
python-socketio: Binary attachment accumulation can cause denial of service this entry
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