CVE-2026-48809python-engineio has possible denial of service due to maximum payload size sometimes not being enforced
Updated under an hour ago ()
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No exploitation reported and no EPSS estimate yet.
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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
- 7.5 HIGH (v3.1, CNA)CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:N/I:N/A:H
- Weakness (CWE)
- CWE-770
- Known exploited
- Not in CISA's KEV catalog
- EPSS (exploitation in the next 30 days)
- Not loaded for this CVE
- Assigned by
- GitHub_M
- NVD analysis
- Deferred
- Record last updated
- Aug 11, 2026
- First seen by InfoSec Signals
- Oct 9, 2026
Affected products
miguelgrinberg python-engineio miguelgrinberg:python_engineio (from the name) | before 4.13.2 | CNA record |
References
- https://github.com/miguelgrinberg/python-engineio/security/advisories/GHSA-m9gh-vj53-gvh9x-refsource-confirm
- https://github.com/pypa/advisory-database/tree/main/vulns/python-engineio/PYSEC-2026-3033.yamlx-refsource-misc
The CVE record on cve.org NVD's entry
The CVE record is authoritative. Products marked “from the name” were identified from the CNA's free-text names, not a CPE, and are matched less certainly. This product uses the NVD API but is not endorsed or certified by the NVD.