← Vulnerability feed

Vulnerability record · CVE-2026-48809 · published 11 August 2026

CVE-2026-48809: Allocation without limits vulnerability

python-engineio is a Python implementation of the Engine.IO realtime client and server. Versions prior to 4.13.2 have two specific configurations of the python-engineio server in which the size of incoming messages is not checked before the messages are loaded into memory. An attacker can take advantage of these to cause unnecessary memory allocations in the python-engineio server. The two cases are POST requests, when using ASGI with the long polling transport and WebSocket messages, when using Aiohttp with the WebSocket transport. Version 4.13.2 addresses this issue. ASGI severs now only load the body of incoming requests into memory after the client is confirmed to be known and authenticated, and the payload size is below the maximum allowed size. Requests that do not comply with these requirements are discarded. Aiohttp servers configure the maximum payload size in the underlying WebSocket layer from Aiohttp, so that large messages are discarded by Aiohttp before they are delivered to python-engineio.

7.5 CVSS 3.1 High EPSS 0.49% · top 60.5% CWE-770 · Allocation without limits Deferred
7.5CVSS 3.1 base score
0.49%EPSS exploitation probability, 30 days
NoNot in CISA KEV
0Affected product versions listed by NVD
2References
18 Sep 2026Last modified by NVD

Description

python-engineio is a Python implementation of the Engine.IO realtime client and server. Versions prior to 4.13.2 have two specific configurations of the python-engineio server in which the size of incoming messages is not checked before the messages are loaded into memory. An attacker can take advantage of these to cause unnecessary memory allocations in the python-engineio server. The two cases are POST requests, when using ASGI with the long polling transport and WebSocket messages, when using Aiohttp with the WebSocket transport. Version 4.13.2 addresses this issue. ASGI severs now only load the body of incoming requests into memory after the client is confirmed to be known and authenticated, and the payload size is below the maximum allowed size. Requests that do not comply with these requirements are discarded. Aiohttp servers configure the maximum payload size in the underlying WebSocket layer from Aiohttp, so that large messages are discarded by Aiohttp before they are delivered to python-engineio.

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

References

LinkTags
https://github.com/miguelgrinberg/python-engineio/security/advisories/GHSA-m9gh-vj53-gvh9
https://github.com/pypa/advisory-database/tree/main/vulns/python-engineio/PYSEC-2026-3033.yaml

Track CVE-2026-48809 inside VULONE

Watch it alongside the ransomware crews, C2 infrastructure and forum chatter that reference it, query it through the API and pull it into your SIEM over TAXII.

Start free Open in platform

Related vulnerabilities

Same products first, then exploited flaws of the same weakness class.

8.6CVE-2020-3569Cisco IOS XR DVMRP IGMP packet handling memory exhaustionCisco IOS XR Software mishandles IGMP packets in its Distance Vector Multicast Routing Protocol (DVMRP) feature, allowing crafted traffic to crash th…KEVEPSS 3.3%analysed8.6CVE-2020-3566Cisco IOS XR DVMRP IGMP queue flaw causes memory exhaustionCisco IOS XR Software mishandles queue management for IGMP packets in its DVMRP feature, allowing uncontrolled memory consumption. An unauthenticated…KEVEPSS 3.7%analysed

Source: NIST National Vulnerability Database (record CVE-2026-48809), CISA KEV, FIRST EPSS (scores of 2026-09-26). This page is refreshed as NVD updates the record.