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Advisory record · GHSA-m9gh-vj53-gvh9

python-engineio has possible denial of service due to maximum payload size sometimes not being enforced

CVSS 7.5 HighEPSS 0.0049 · 42nd percentile

Published by the GitHub Advisory Database at 26 Jun 2026, 20:48 UTC. agentprime has not analysed this yet, so whether it affects any app is not known.

PackageEcosystemAffectedFixed in
python-engineioPyPI<4.13.24.13.2
Identifiers
GHSA-m9gh-vj53-gvh9 · CVE-2026-48809 · PYSEC-2026-3033
Weakness (CWE)
CWE-770
Tags
Published
26 Jun 2026
Updated
13 Jul 2026

Machine-written summary

Summary written by Claude Haiku from the source advisory. Not reviewed by a person.

Versions of python-engineio before 4.13.2 do not always enforce the maximum payload size on incoming messages. In ASGI deployments using long polling POST requests, and in Aiohttp deployments using the WebSocket transport, large messages can be loaded into memory before the size check. An attacker able to send such requests can force unnecessary memory allocations, which may cause a denial of service. Upgrade to python-engineio 4.13.2 or later.

Written 6 Nov 2026.

Not analysed yet

We haven’t published our analysis of this Advisory yet. Once a person has reviewed it, this page will say what’s vulnerable, what has to be true for your app to be affected, and how to check.

Severity and exploitation

ScoreRatingCVSSVectorSource
7.5 High 3.1 CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:N/I:N/A:H CNA (GitHub_M)
  • CISA KEV Not listed.
  • EPSS 0.0049, the 42nd percentile, on 15 Nov 2026: FIRST’s estimate of the chance of exploitation in the next 30 days.

Timeline

  1. 31 Oct 2026, 15:01 UTC First seen by agentprime
  2. 31 Oct 2026, 15:01 UTC Confirmed by OSV

Sources

Facts on this page come from the GitHub Advisory Database (CC-BY 4.0), OSV and the other sources listed, as published. We don’t reproduce full advisory descriptions, which can contain exploit code.