EUVD-2026-56859
GHSA-cgwc-pv48-fhj5
Severity by source
AV:N/AC:L/PR:N/UI:N/S:U/C:N/I:N/A:H
Network-reachable Engine.IO endpoint, low-complexity PONG flooding, no auth required in default deployments, availability-only DoS with no confidentiality or integrity impact.
Primary rating from Vendor (https://github.com/miguelgrinberg/python-engineio).
CVSS VectorVendor: https://github.com/miguelgrinberg/python-engineio
Lifecycle Timeline
2DescriptionCVE.org
Impact
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.
Note: 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.
Patches
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
connecthandler. - 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.
Articles & Coverage 1
AnalysisAI
Denial of service in the python-engineio server (versions <= 4.13.1) allows remote unauthenticated attackers to exhaust server resources by abusing the heartbeat mechanism, which spawns a new background thread on each connection and on every PONG packet received. Synchronous servers are most at risk because each heartbeat is a physical OS thread; asynchronous deployments allocate lightweight tasks and are far less affected. No public exploit has been identified at the time of analysis, and the issue is not listed in CISA KEV; a vendor-released patch (version 4.13.2) is available.
Technical ContextAI
python-engineio is the Python implementation of the Engine.IO transport protocol, the low-level long-polling/WebSocket layer that underpins python-socketio and powers real-time bidirectional communication in many Python web applications. Engine.IO uses a PING/PONG heartbeat to detect dead connections: the server launches a background worker to manage the heartbeat when a connection is established, and the flawed logic also launched a fresh worker each time a client sent a PONG packet. This maps to CWE-770 (Allocation of Resources Without Limits or Throttling) - the server placed no cap on the number of concurrently allocated heartbeat threads, so a client controlling PONG traffic could drive unbounded thread creation. In synchronous mode each such thread is a real OS thread with non-trivial memory and scheduling cost, making resource exhaustion realistic; in asynchronous mode the same flaw allocates coroutine tasks, which are cheap but were still fixed for completeness.
RemediationAI
Vendor-released patch: 4.13.2 - upgrade python-engineio to 4.13.2 or later (for example via 'pip install --upgrade python-engineio>=4.13.2'), per the advisory at https://github.com/miguelgrinberg/python-engineio/security/advisories/GHSA-cgwc-pv48-fhj5. The fix ensures the heartbeat worker is only started after a client passes authentication in the connect handler and guarantees at most one heartbeat worker per client, discarding out-of-sequence PONG packets while one is active. If immediate upgrade is not possible, implement authentication in your connect handler so unauthenticated clients cannot trigger worker allocation (trade-off: requires application code changes and only the post-4.13.2 logic fully enforces the single-worker guarantee); for synchronous deployments, prefer an asynchronous server backend to reduce per-connection cost, and place a reverse proxy or rate limiter in front of the Engine.IO endpoint to throttle connection and PONG volume per client (trade-off: may affect legitimate high-frequency clients and does not eliminate the underlying unbounded allocation).
Wazuh SIEM platform versions 4.4.0 through 4.9.0 contain an unsafe deserialization vulnerability in the DistributedAPI t
BentoML version 1.4.2 and earlier contains an unauthenticated remote code execution vulnerability through insecure deser
pgAdmin 4 contains critical remote code execution vulnerabilities in the Query Tool download and Cloud Deployment endpoi
The renderLocalView function in render/views.py in graphite-web in Graphite 0.9.5 through 0.9.10 uses the pickle Python
BentoML is a Python library for building online serving systems optimized for AI apps and model inference. Rated critica
OpenSSL before 0.9.8za, 1.0.0 before 1.0.0m, and 1.0.1 before 1.0.1h does not properly restrict processing of ChangeCiph
pyLoad download manager version prior to 0.5.0b3.dev77 exposes the Flask SECRET_KEY through an unauthenticated endpoint.
Langflow (a visual LLM pipeline builder) contains a critical unauthenticated code execution vulnerability (CVE-2026-3301
In Mercurial before 4.1.3, "hg serve --stdio" allows remote authenticated users to launch the Python debugger, and conse
Unauthenticated remote code execution affects Kestra OSS (the open-source event-driven orchestration platform) prior to
Unauthenticated remote code execution in Marimo ≤0.20.4 allows attackers to execute arbitrary system commands via the `/
pyLoad is the free and open-source Download Manager written in pure Python. Rated medium severity (CVSS 5.3), this vulne
Same technique Denial Of Service
View allVendor StatusVendor
SUSE
Severity: Important| Product | Status |
|---|---|
| SUSE Linux Enterprise Desktop 15 SP7 SUSE Linux Enterprise High Performance Computing 15 SP7 SUSE Linux Enterprise Module for Python 3 15 SP7 SUSE Linux Enterprise Server 15 SP7 SUSE Linux Enterprise Server for SAP Applications 15 SP7 | Fixed |
| SUSE Linux Enterprise Server 15 SP6-LTSS | Fixed |
| SUSE Linux Enterprise Server for SAP Applications 15 SP6 | Fixed |
| openSUSE Leap 16.0 | Fixed |
| SUSE Linux Enterprise Desktop 15 SP7 | Affected |
| SUSE Linux Enterprise High Performance Computing 15 SP7 | Affected |
| SUSE Linux Enterprise Module for Python 3 15 SP7 | Affected |
| SUSE Linux Enterprise Server 15 SP7 | Affected |
| SUSE Linux Enterprise Server for SAP Applications 15 SP7 | Affected |
| SUSE Linux Enterprise Module for Python 3 15 SP6 | Affected |
| SUSE Linux Enterprise Server 15 SP6 | Affected |
| SUSE Linux Enterprise Server 15 SP6-LTSS | Affected |
| SUSE Linux Enterprise Server for SAP Applications 15 SP6 | Affected |
| SUSE Linux Enterprise Desktop 15 SP6 | Affected |
| SUSE Linux Enterprise High Performance Computing 15 SP6 | Affected |
| openSUSE Leap 15.6 | Affected |
Share
External POC / Exploit Code
Leaving vuln.today