CVE-2026-48802
python-engineio has unbound thread allocation that can cause denial of service
Description
python-engineio is a Python implementation of the Engine.IO realtime client and server. Prior to version 4.13.2, an attacker can cause the creation of unnecessary background threads in the python-engineio server by exploiting the heartbeat mechanism, which launches a thread when a new connection is received, and when the client sends a PONG packet. This issue primarily affects synchronous servers. Asynchronous servers allocate background tasks instead of physical threads, which are lightweight and less likely to cause denial of service. However, the fix that was implemented was also applied to the asynchronous case. Version 4.13.2 addresses this issue as follows: The initial background thread (or async task( for heartbeat management is only launched if a client passes authentication in the `connect` handler; and the server now ensures that there is only one background heatbeat thread (or async task) per client at a given point in time. Out of sequence PONG packets are now discarded when an active heartbeat thread is already running.
INFO
Published Date :
Aug. 11, 2026, 7:17 p.m.
Last Modified :
Aug. 11, 2026, 7:17 p.m.
Remotely Exploit :
Yes !
Source :
[email protected]
Affected Products
The following products are affected by CVE-2026-48802
vulnerability.
Even if cvefeed.io is aware of the exact versions of the
products
that
are
affected, the information is not represented in the table below.
CVSS Scores
| Score | Version | Severity | Vector | Exploitability Score | Impact Score | Source |
|---|---|---|---|---|---|---|
| CVSS 3.1 | HIGH | [email protected] | ||||
| CVSS 3.1 | HIGH | MITRE-CVE |
Solution
- Update python-engineio to version 4.13.2 or newer.
- Ensure clients pass authentication before starting heartbeat threads.
- Discard out-of-sequence PONG packets during active heartbeats.
References to Advisories, Solutions, and Tools
Here, you will find a curated list of external links that provide in-depth
information, practical solutions, and valuable tools related to
CVE-2026-48802.
| URL | Resource |
|---|---|
| https://github.com/miguelgrinberg/python-engineio/security/advisories/GHSA-cgwc-pv48-fhj5 | |
| https://github.com/pypa/advisory-database/tree/main/vulns/python-engineio/PYSEC-2026-3032.yaml |
CWE - Common Weakness Enumeration
While CVE identifies
specific instances of vulnerabilities, CWE categorizes the common flaws or
weaknesses that can lead to vulnerabilities. CVE-2026-48802 is
associated with the following CWEs:
Common Attack Pattern Enumeration and Classification (CAPEC)
Common Attack Pattern Enumeration and Classification
(CAPEC)
stores attack patterns, which are descriptions of the common attributes and
approaches employed by adversaries to exploit the CVE-2026-48802
weaknesses.
We scan GitHub repositories to detect new proof-of-concept exploits. Following list is a collection of public exploits and proof-of-concepts, which have been published on GitHub (sorted by the most recently updated).
Results are limited to the first 15 repositories due to potential performance issues.
The following list is the news that have been mention
CVE-2026-48802 vulnerability anywhere in the article.
The following table lists the changes that have been made to the
CVE-2026-48802 vulnerability over time.
Vulnerability history details can be useful for understanding the evolution of a vulnerability, and for identifying the most recent changes that may impact the vulnerability's severity, exploitability, or other characteristics.
-
New CVE Received by [email protected]
Aug. 11, 2026
Action Type Old Value New Value Added Affected [{'vendor': 'miguelgrinberg', 'product': 'python-engineio', 'versions': [{'status': 'affected', 'version': '< 4.13.2'}]}] Added Description python-engineio is a Python implementation of the Engine.IO realtime client and server. Prior to version 4.13.2, an attacker can cause the creation of unnecessary background threads in the python-engineio server by exploiting the heartbeat mechanism, which launches a thread when a new connection is received, and when the client sends a PONG packet. This issue primarily affects synchronous servers. Asynchronous servers allocate background tasks instead of physical threads, which are lightweight and less likely to cause denial of service. However, the fix that was implemented was also applied to the asynchronous case. Version 4.13.2 addresses this issue as follows: The initial background thread (or async task( for heartbeat management is only launched if a client passes authentication in the `connect` handler; and the server now ensures that there is only one background heatbeat thread (or async task) per client at a given point in time. Out of sequence PONG packets are now discarded when an active heartbeat thread is already running. Added CVSS V3.1 AV:N/AC:L/PR:N/UI:N/S:U/C:N/I:N/A:H Added CWE CWE-770 Added Reference https://github.com/miguelgrinberg/python-engineio/security/advisories/GHSA-cgwc-pv48-fhj5 Added Reference https://github.com/pypa/advisory-database/tree/main/vulns/python-engineio/PYSEC-2026-3032.yaml