CVE-2026-48804 python-socketio: Binary attachment accumulation can cause denial of service
An attacker can cause a denial of service by sending binary messages with missing attachments, forcing the server to retain them in memory indefinitely.
- Exploited in the wild
- Not known
- Login needed
- Not needed
- Attackable
- Over the internet
- Victim action needed
- Not needed
- Fix
- Available
What is CVE-2026-48804?
CVE-2026-48804 is a high-severity denial of service vulnerability in miguelgrinberg python-socketio, published on 11 Aug 2026. An attacker can exploit it over the internet without logging in, with no action from the victim.
Official description
python-socketio is a Python implementation of the Socket.IO realtime client and server. 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. Prior to version 5.16.4, 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. Version 5.16.4 takes the following measures to address this issue: Binary packets are only accepted from authenticated clients and, when a client disconnects, the server checks if there is a partial binary message being held for the client and deletes it.
Weakness: CWE-770
Which versions are affected by CVE-2026-48804?
3 open source packages ship an affected version, including python-socketio.
| Package | Affected | Fixed in |
|---|---|---|
python-socketio PyPI | All versions | 5.16.2 |
python-socketio PyPI | All versions | 5.16.2 |
python-socketio PyPI | All versions | 5.16.2 |
Linux distribution packages (4)
python-python-socketio SUSE:Linux Enterprise Module for Python 3 15 SP7 | All versions | 5.7.2-150600.3.6.1 |
python-python-socketio SUSE:Linux Enterprise Server 15 SP6-LTSS | All versions | 5.7.2-150600.3.6.1 |
python-python-socketio SUSE:Linux Enterprise Server for SAP Applications 15 SP6 | All versions | 5.7.2-150600.3.6.1 |
python-python-socketio openSUSE:Tumbleweed | All versions | 5.16.3-1.1 |
How do I fix CVE-2026-48804?
Upgrade python-socketio to 5.16.2 or later.
Upgrade, then put limits on request size, rate and nesting depth so one client cannot exhaust the service. More about Denial of service.
Is CVE-2026-48804 being exploited?
There is no known exploitation of CVE-2026-48804 in the wild and no public exploit code.
Sources
Also known as DEBIAN-CVE-2026-48804, GHSA-5w7q-77mv-v69f, PYSEC-2026-3042, ROOT-APP-PYPI-CVE-2026-48804, SUSE-SU-2026:3086-1, UBUNTU-CVE-2026-48804 and 1 more.