socket.io allows an unbounded number of binary attachments

Description

Impact

A specially crafted Socket.IO packet can make the server wait for a large number of binary attachments and buffer them, which can be exploited to make the server run out of memory.

Patches

Version range Used by Fixed version
>=4.0.0 <4.2.6 [email protected] and [email protected] 4.2.6
>=3.4.0 <3.4.4 [email protected] 3.4.4
<3.3.5 [email protected] 3.3.5

Workarounds

There is no known workaround except upgrading to a safe version.

For more information

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Basic information

Type
reviewed
Severity
high
Advisory on GitHub
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Repository advisory
Open repository advisory ↗
Source code
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Published (advisory)
2026-03-18 17:26:14 UTC
Updated
2026-03-20 21:33:54 UTC
GitHub reviewed
2026-03-18 17:26:14 UTC
NVD published
2026-03-20

EPSS Score

Score Percentile
0.17% 38.48%

CVSS Scores

Base score Version Severity Vector
8.7 4.0
CVSS:4.0/AV:N/AC:L/AT:N/PR:N/UI:N/VC:N/VI:N/VA:H/SC:N/SI:N/SA:N Click to expand
Attack vector (AV:N)
Could be attacked over the internet or any normal routed network.
Attack complexity (AC:L)
Exploitation conditions are straightforward and stable.
Attack requirements (AT:N)
No additional preconditions are required beyond normal reachability.
Privileges required (PR:N)
No privileges are required.
User interaction (UI:N)
No user interaction is required.
Vulnerable system confidentiality impact (VC:N)
No confidentiality impact on the vulnerable system.
Vulnerable system integrity impact (VI:N)
No integrity impact on the vulnerable system.
Vulnerable system availability impact (VA:H)
High availability impact on the vulnerable system.
Subsequent system confidentiality impact (SC:N)
No confidentiality impact on subsequent systems.
Subsequent system integrity impact (SI:N)
No integrity impact on subsequent systems.
Subsequent system availability impact (SA:N)
No availability impact on subsequent systems.

Identifiers

CWEs

CWE id Name
CWE-754 Improper Check for Unusual or Exceptional Conditions

Credits

  • x4cc3 (reporter)
  • darrachequesne (analyst)

Affected packages (3)

Vulnerable version ranges and first patched releases as published by GitHub.

Ecosystem Package Vulnerable range First patched Vulnerable functions
npm socket.io-parser < 3.3.5 3.3.5
npm socket.io-parser >= 3.4.0, < 3.4.4 3.4.4
npm socket.io-parser >= 4.0.0, < 4.2.6 4.2.6

References

cvelogic Threat Intelligence