CVE-2026-40879Network attack vector

Unauthenticated process crash via recursive JSON handling

Published Apr 21, 2026 · Updated Apr 21, 2026

Uncontrolled recursion in NestJS Nest before 11.1.19 allows remote attackers to crash TCP microservices with bundled JSON messages. JsonSocket.handleData() recursively processes each valid JSON message while shrinking its buffer, so the configured maximum buffer size does not stop stack growth. A single approximately 47 KB TCP frame can exhaust the Node.js call stack and raise RangeError without authentication or user interaction, interrupting the affected process.

CVSS severity7.5
High
EPSS probability0.33%
Next 30 days · Sep 16, 2026
Known exploitationUnconfirmed
Based on sourced intelligence
Hinoki checkNot available
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Summary

What happened

Uncontrolled recursion in NestJS Nest before 11.1.19 allows remote attackers to crash TCP microservices with bundled JSON messages. JsonSocket.handleData() recursively processes each valid JSON message while shrinking its buffer, so the configured maximum buffer size does not stop stack growth. A single approximately 47 KB TCP frame can exhaust the Node.js call stack and raise RangeError without authentication or user interaction, interrupting the affected process.

The record

CVE
CVE-2026-40879
Published
Apr 21, 2026
Updated
Apr 21, 2026
Vendor
NestJS
Product
Nest
Classifications
CWE-674, CWE-770, T1499.003
Attack vector
network
Privileges
unauthenticated

Timeline

How it unfolded

  1. Apr 21, 2026CVE publishedPublication date reported by the CVE source.
  2. Apr 21, 2026Record updatedLatest update available in the CVE record.

Exploitability

Present is not the same as exploitable

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Is a vulnerable build present?

Compare these published version ranges with your installed build and any vendor patches.

  1. Affected versionversion=< 11.1.19

What conditions does exploitation require?

Attack vectornetwork
Required privilegesunauthenticated

What is affected?

NestJS · Nestversion=< 11.1.19

Published CVSS scores

7.5GitHub, Inc.CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:N/I:N/A:H

CVSS describes severity. EPSS estimates exploitation probability.

Attacks

What attackers are doing with it

Daily unique IPs observed by Shadowserver honeypots for known exploited vulnerabilities (KEVs). Missing observations do not establish an absence of attacks.

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No observations available

Sep 10, 2026Sep 16, 2026
Latest reporting daySep 16, 2026
Latest daily unique IPsUnavailable
Prior 30-day averageUnavailable
SourceShadowserver honeypots (KEV)
Vectornetwork
Privilegesunauthenticated
Known exploitationUnconfirmed
Public exploitUnconfirmed

Weakness, pattern, technique

CWE-674Uncontrolled Recursion
CWE-770Allocation of Resources Without Limits or Throttling
T1499.003Application Exhaustion Flood

Public exploit references

No public exploit references are available in this record.

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Technologies

Your stack

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Your stack

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