python-socketio: Binary attachment accumulation can cause denial of service (CVE-2026-48804) | HOL Guard CVE

High · CVSS 7.5CVE-2026-48804GHSA-5W7Q-77MV-V69F

python-socketio: Binary attachment accumulation can cause denial of service

Answer in brief

CVE-2026-48804 records a High severity (CVSS 7.5) vulnerability in python-socketio: Binary attachment accumulation can cause denial of service. The current sources do not mark it as known exploited. The current feed maps miguelgrinberg/python-socketio (generic), python-socketio (pip). Check affected ranges and fixed versions before updating.

Analysis pending evidence review

HOL Guard separates source facts from reviewed analysis. See the methodology.

Published Aug 11, 2026Updated Sep 10, 2026Source checked Sep 17, 2026First seen by HOL Jun 26, 2026Material review Sep 10, 2026

Upstream Advisory

Key facts

Risk: High · CVSS 7.5
Exploitation: Not marked as known exploited
Affected software: 2 mapped packages or products
Fix availability: Available

Why this deserves its current priority

CVSS is 7.5. The current sources do not mark it as known exploited. Treat this as a source-backed prioritization signal, not a statement about your environment.

Analysis status

Analysis pending evidence review

Factual feed record only; HOL analysis is not approved for indexing. Read the methodology.

Affected scope and exposure questions

The current feed maps miguelgrinberg/python-socketio (generic), python-socketio (pip). Check affected ranges and fixed versions before updating.

Mapped affected packages and fixed versions
Package	Affected range	Fixed version
miguelgrinberg/python-socketiogeneric	< 5.16.4	Not reported
python-socketiopip	<=5.16.1	5.16.2

Recommended response

Check inventory. Check lockfiles and deployed manifests for miguelgrinberg/python-socketio, python-socketio.
Review the reported fix. Update python-socketio to 5.16.2 if you use the affected versions. Test the change in a non-production environment first.

Evidence timeline and material changes

Published upstream
Aug 11, 2026
Evidence: source:cvelist:source_dates:source-dates:record
Source modified
Sep 10, 2026
Evidence: source:cvelist:source_dates:source-dates:record
First seen by HOL
Jun 26, 2026

Sources and claim methodology

Upstream source 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.

Quoted source text, attributed separately from HOL analysis.