python-engineio — security advisory
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.
- Products
- python-engineio
- Affected versions
- 4.11.1-0.1, 4.11.2-1, 4.12.1-1, 4.12.1-2, 4.13.0-1, 4.13.0-2, 4.14.0-1, 4.3.4-2, 4.3.4-2.1, 4.9.0-1, 4.9.0-2
- Fixed versions
- 4.14.0-1
- CVEs
- CVE-2026-48802
- Confirmed fixed CVEs
- Not specified
- Updated in this feed
- 28 Oct 2026, 09:00 UTC · Revision 1
Source evidence
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.
osv:DEBIAN-CVE-2026-48802
python-engineio
Fixed versions: Not specified
python-engineio
Fixed versions: Not specified
python-engineio
Fixed versions: 4.14.0-1
Complete source record
{
"id": "94d009e2e52bec017c9e06037809f02ae028e84e2e3487927fb019a04b9ef830",
"url": "https://osv.dev/vulnerability/DEBIAN-CVE-2026-48802",
"method": "structured",
"payload": {
"kind": "advisory",
"title": "DEBIAN-CVE-2026-48802",
"summary": "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.",
"evidence": "osv:DEBIAN-CVE-2026-48802",
"products": [
{
"name": {
"value": "python-engineio",
"evidence": "/affected/0/package/name"
},
"prerequisites": [],
"fixed_versions": [],
"affected_versions": [
{
"value": "4.11.1-0.1",
"evidence": "/affected/0/versions"
},
{
"value": "4.11.2-1",
"evidence": "/affected/0/versions"
},
{
"value": "4.12.1-1",
"evidence": "/affected/0/versions"
},
{
"value": "4.12.1-2",
"evidence": "/affected/0/versions"
},
{
"value": "4.13.0-1",
"evidence": "/affected/0/versions"
},
{
"value": "4.13.0-2",
"evidence": "/affected/0/versions"
},
{
"value": "4.14.0-1",
"evidence": "/affected/0/versions"
},
{
"value": "4.3.4-2",
"evidence": "/affected/0/versions"
},
{
"value": "4.3.4-2.1",
"evidence": "/affected/0/versions"
},
{
"value": "4.9.0-1",
"evidence": "/affected/0/versions"
},
{
"value": "4.9.0-2",
"evidence": "/affected/0/versions"
}
]
},
{
"name": {
"value": "python-engineio",
"evidence": "/affected/1/package/name"
},
"prerequisites": [],
"fixed_versions": [],
"affected_versions": [
{
"value": "4.11.2-1",
"evidence": "/affected/1/versions"
},
{
"value": "4.12.1-1",
"evidence": "/affected/1/versions"
},
{
"value": "4.12.1-2",
"evidence": "/affected/1/versions"
},
{
"value": "4.13.0-1",
"evidence": "/affected/1/versions"
},
{
"value": "4.13.0-2",
"evidence": "/affected/1/versions"
},
{
"value": "4.14.0-1",
"evidence": "/affected/1/versions"
}
]
},
{
"name": {
"value": "python-engineio",
"evidence": "/affected/2/package/name"
},
"prerequisites": [],
"fixed_versions": [
{
"value": "4.14.0-1",
"evidence": "/affected/2/ranges"
}
],
"affected_versions": [
{
"value": "4.11.2-1",
"evidence": "/affected/2/versions"
},
{
"value": "4.12.1-1",
"evidence": "/affected/2/versions"
},
{
"value": "4.12.1-2",
"evidence": "/affected/2/versions"
},
{
"value": "4.13.0-1",
"evidence": "/affected/2/versions"
},
{
"value": "4.13.0-2",
"evidence": "/affected/2/versions"
}
]
}
],
"severity": "high",
"structured": {
"id": "DEBIAN-CVE-2026-48802",
"aliases": [
"DEBIAN-CVE-2026-48802"
],
"metrics": [
{
"type": "CVSS_V3",
"score": "CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:N/I:N/A:H"
}
],
"affected": [
{
"ranges": [
{
"type": "ECOSYSTEM",
"events": [
{
"introduced": "0"
}
]
}
],
"package": {
"name": "python-engineio",
"purl": "pkg:deb/debian/python-engineio?arch=source&distro=bookworm",
"ecosystem": "Debian:12"
},
"versions": [
"4.11.1-0.1",
"4.11.2-1",
"4.12.1-1",
"4.12.1-2",
"4.13.0-1",
"4.13.0-2",
"4.14.0-1",
"4.3.4-2",
"4.3.4-2.1",
"4.9.0-1",
"4.9.0-2"
],
"database_specific": {
"source": "https://storage.googleapis.com/debian-osv/debian-cve-osv/DEBIAN-CVE-2026-48802.json"
},
"ecosystem_specific": {
"urgency": "not yet assigned"
}
},
{
"ranges": [
{
"type": "ECOSYSTEM",
"events": [
{
"introduced": "0"
}
]
}
],
"package": {
"name": "python-engineio",
"purl": "pkg:deb/debian/python-engineio?arch=source&distro=trixie",
"ecosystem": "Debian:13"
},
"versions": [
"4.11.2-1",
"4.12.1-1",
"4.12.1-2",
"4.13.0-1",
"4.13.0-2",
"4.14.0-1"
],
"database_specific": {
"source": "https://storage.googleapis.com/debian-osv/debian-cve-osv/DEBIAN-CVE-2026-48802.json"
},
"ecosystem_specific": {
"urgency": "not yet assigned"
}
},
{
"ranges": [
{
"type": "ECOSYSTEM",
"events": [
{
"introduced": "0"
},
{
"fixed": "4.14.0-1"
}
]
}
],
"package": {
"name": "python-engineio",
"purl": "pkg:deb/debian/python-engineio?arch=source&distro=forky",
"ecosystem": "Debian:14"
},
"versions": [
"4.11.2-1",
"4.12.1-1",
"4.12.1-2",
"4.13.0-1",
"4.13.0-2"
],
"database_specific": {
"source": "https://storage.googleapis.com/debian-osv/debian-cve-osv/DEBIAN-CVE-2026-48802.json"
},
"ecosystem_specific": {
"urgency": "not yet assigned"
}
}
],
"modified": "2026-10-08T06:00:07.201741257Z",
"provider": "osv",
"upstream": [
"CVE-2026-48802"
],
"references": [
"https://security-tracker.debian.org/tracker/CVE-2026-48802"
]
},
"related_cves": [
{
"value": "CVE-2026-48802",
"evidence": "/upstream"
}
],
"security_relevant": true,
"severity_evidence": "/severity/0/score"
},
"source_id": "core-osv",
"document_id": 98601,
"published_at": "2026-08-11T19:17:37.12+00:00"
}