Resource exhaustion in engine.io

published 2021-01-07 5 y ago modified 2026-06-17 4 mo ago also GHSA-j4f2-536g-r55m , EUVD-2022-1064

cvss: 7.5; version 3.1, NVD
cisa kev: Not listed; not in CISA's catalog
epss: 3.3%; EPSS 3.3% chance of exploitation in 30 days, percentile 88%
public exploits: 0; none known

Engine.IO before 4.0.0 allows attackers to cause a denial of service (resource consumption) via a POST request to the long polling transport.

Patch / fix

fixed in 2 links 2

npm engine.io 3.6.0
socket engine.io 4.0.0

github.com/socketio/engine.io@734f9d1 commit
github.com/socketio/engine.io@58e274c commit

Vendor advisories

What the vendors themselves say about their products: affected, fixed or not affected, and what to do.

red hat product security vex CVE-2020-36048 updated 2026-06-28 cvss 7.5

yarnpkg-socket.io/engine.io: allows attackers to cause a denial of service (resource consumption) via a POST request to the long polling transport

Red Hat Quay 3 quay/quay-rhel8, quay/quay-builder-qemu-rhcos-rhel8
affected: no fix available “Fix deferred”

Red Hat CSAF VEX © Red Hat, Inc., from https://security.access.redhat.com/data/csaf/v2/vex/; changed: reduced to product statuses and remediations. CC BY 4.0 · csaf

Exploit prediction

3.28% chance of exploitation in the next 30 days, higher than 88% of all scored CVEs (FIRST EPSS, 2026-11-08).

Exploits and checks

blog.caller.xyz https://blog.caller.xyz/socketio-engineio-dos/ referenced PoC, tagged "exploit" by a source, unverified

CVSS scores

assigned by	version	score	vector
NVD	3.1	7.5	CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:N/I:N/A:H
NVD	2.0	5.0	AV:N/AC:L/Au:N/C:N/I:N/A:P
GitHub	3.1	7.5	CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:N/I:N/A:H

Affected packages

ecosystem	package	affected	fixed in
npm	engine.io	<3.6.0	3.6.0

Classification

Weakness

CWE-400 Uncontrolled Resource Consumption

References

github.com /socketio/engine.io/commit/734f9d1268840722c41219e69eb58318e0b2ac6b
web, patch, third-party-advisory
github.com /socketio/engine.io/commit/58e274c437e9cbcf69fd913c813aad8fbd253703
web
blog.caller.xyz /socketio-engineio-dos/
exploit, third-party-advisory
github.com /bcaller/kill-engine-io
web, third-party-advisory
nvd.nist.gov /vuln/detail/CVE-2020-36048
advisory
blog.caller.xyz /socketio-engineio-dos
web
github.com /socketio/engine.io
package

Sources

Fencer Vulns keeps one entry per vulnerability: the CVE id wins, then GHSA, and records that alias each other are merged, except that two CVEs always keep separate entries. The same data is available as JSON.

Summary