CVE-2026-40879 Nest: DoS via Recursive handleData in JsonSocket (TCP Transport)
An attacker can cause a stack overflow and denial of service in Nest applications by sending crafted TCP frames with many small JSON messages.
- Exploited in the wild
- Not known
- Login needed
- Not needed
- Attackable
- Over the internet
- Victim action needed
- Not needed
- Fix
- Available
What is CVE-2026-40879?
CVE-2026-40879 is a high-severity denial of service vulnerability in nestjs nest, published on 21 Apr 2026. An attacker can exploit it over the internet without logging in, with no action from the victim.
Official description
Nest is a framework for building scalable Node.js server-side applications. Prior to 11.1.19, when an attacker sends many small, valid JSON messages in one TCP frame, handleData() recurses once per message; the buffer shrinks each call. maxBufferSize is never reached; call stack overflows instead. A ~47 KB payload is sufficient to trigger RangeError. This vulnerability is fixed in 11.1.19.
Weakness: CWE-674
Which versions are affected by CVE-2026-40879?
2 open source packages ship an affected version, including @nestjs/microservices. It affects 1 product.
| Package | Affected | Fixed in |
|---|---|---|
@nestjs/microservices npm | All versions | 11.1.19 |
@nestjs/microservices npm | All versions | 11.1.19 |
Products include Nestjs Nest.
How do I fix CVE-2026-40879?
Upgrade @nestjs/microservices to 11.1.19 or later.
Upgrade, then put limits on request size, rate and nesting depth so one client cannot exhaust the service. More about Denial of service.
Is CVE-2026-40879 being exploited?
There is no known exploitation of CVE-2026-40879 in the wild and no public exploit code.
Other vulnerabilities in nestjs nest
- CVE-2026-33011 Nest Fastify HEAD Request Middleware Bypass
- CVE-2026-2293 NestJS 11.1.13 - Lack of data validation allowing authentication/authorization bypass
- CVE-2025-69211 Nest has a Fastify URL Encoding Middleware Bypass (TOCTOU)
- CVE-2026-35515 @nestjs/core Improperly Neutralizes Special Elements in Output Used by a Downstream Component ('Injection')
- CVE-2024-29409 nest allows a remote attacker to execute arbitrary code via the Content-Type header
Sources
Also known as GHSA-hpwf-8g29-85qm.