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Socket.IO: Zero-attachment Memory Exhaustion

High severity GitHub Reviewed Published Jul 24, 2026 in socketio/socket.io • Updated Aug 3, 2026

Package

npm socket.io-parser (npm)

Affected versions

>= 4.0.0, < 4.2.7
>= 3.4.0, < 3.4.5
< 3.3.6

Patched versions

4.2.7
3.4.5
3.3.6

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 <4.2.7 socket.io@4.x and socket.io-client@4.x 4.2.7
>=3.4.0 <3.4.5 socket.io@2.x 3.4.5
<3.3.6 socket.io-client@2.x 3.3.6

Workarounds

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

For more information

If you have any questions or comments about this advisory:

  • Open a discussion here

References

@darrachequesne darrachequesne published to socketio/socket.io Jul 24, 2026
Published to the GitHub Advisory Database Aug 3, 2026
Reviewed Aug 3, 2026
Last updated Aug 3, 2026

Severity

High

CVSS overall score

This score calculates overall vulnerability severity from 0 to 10 and is based on the Common Vulnerability Scoring System (CVSS).
/ 10

CVSS v3 base metrics

Attack vector
Network
Attack complexity
Low
Privileges required
None
User interaction
None
Scope
Unchanged
Confidentiality
None
Integrity
None
Availability
High

CVSS v3 base metrics

Attack vector: More severe the more the remote (logically and physically) an attacker can be in order to exploit the vulnerability.
Attack complexity: More severe for the least complex attacks.
Privileges required: More severe if no privileges are required.
User interaction: More severe when no user interaction is required.
Scope: More severe when a scope change occurs, e.g. one vulnerable component impacts resources in components beyond its security scope.
Confidentiality: More severe when loss of data confidentiality is highest, measuring the level of data access available to an unauthorized user.
Integrity: More severe when loss of data integrity is the highest, measuring the consequence of data modification possible by an unauthorized user.
Availability: More severe when the loss of impacted component availability is highest.
CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:N/I:N/A:H

EPSS score

Exploit Prediction Scoring System (EPSS)

This score estimates the probability of this vulnerability being exploited within the next 30 days. Data provided by FIRST.
(27th percentile)

Weaknesses

Improper Input Validation

The product receives input or data, but it does not validate or incorrectly validates that the input has the properties that are required to process the data safely and correctly. Learn more on MITRE.

Improper Check for Unusual or Exceptional Conditions

The product does not check or incorrectly checks for unusual or exceptional conditions that are not expected to occur frequently during day to day operation of the product. Learn more on MITRE.

CVE ID

CVE-2026-69185

GHSA ID

GHSA-2m8v-j782-fhvr

Source code

Credits

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