Is CVE-2026-63462 exploited in the wild?

No. Junglewise Threat Intelligence has no report of CVE-2026-63462 being exploited in the wild.

How severe is CVE-2026-63462?

High severity, with a CVSS score of 7.5, published 21 August 2026.

Which products and versions are affected?

unleash-server (npm) SEMVER:introduced=0,fixed=7.5.2.

Is there a fix for CVE-2026-63462?

Yes. unleash-server (npm): upgrade to 7.5.2 or later. Junglewise finds every place you run it, drafts the upgrade and applies it once you approve.

How is CVE-2026-63462 attacked?

It is attacked over the network, in a hosted service.

Am I affected by CVE-2026-63462?

Check whether you run unleash-server (npm) at an affected version. Junglewise does that check for you around the clock: connect your code, cloud and domains, and it matches new vulnerabilities like this one against what you actually run and tells you when one reaches you.

CVE-2026-63462: Unleash server unauthenticated denial of service via deeply nested JSON

CVE-2026-63462 · Severity: high · CVSS 7.5 · Published 2026-08-21

Unleash is a feature-flag management server used to control application behavior in production. An unauthenticated attacker can crash the entire server with a single 10 KB POST request containing deeply-nested JSON sent to any validation endpoint. The server does not recover automatically, and repeated requests can sustain an indefinite outage without a restart policy.

Technologies: unleash-server (npm). Vendors: npm.

Quick answers

Is CVE-2026-63462 exploited in the wild?: No. Junglewise Threat Intelligence has no report of CVE-2026-63462 being exploited in the wild.
How severe is CVE-2026-63462?: High severity, with a CVSS score of 7.5, published 21 August 2026.
Which products and versions are affected?: unleash-server (npm) SEMVER:introduced=0,fixed=7.5.2.
Is there a fix for CVE-2026-63462?: Yes. unleash-server (npm): upgrade to 7.5.2 or later. Junglewise finds every place you run it, drafts the upgrade and applies it once you approve.
How is CVE-2026-63462 attacked?: It is attacked over the network, in a hosted service.
Am I affected by CVE-2026-63462?: Check whether you run unleash-server (npm) at an affected version. Junglewise does that check for you around the clock: connect your code, cloud and domains, and it matches new vulnerabilities like this one against what you actually run and tells you when one reaches you.

How to fix

unleash-server (npm): upgrade to 7.5.2 or later
```
npm install unleash-server@7.5.2
```

Technical details

The vulnerability is an uncontrolled recursion flaw (CWE-674) in the OpenAPI request validation error path. When validation fails, the error formatter in src/lib/error/bad-data-error.ts calls JSON.stringify(propertyValue) directly on request-body data extracted via lodash.get, with no recursion limit or try/catch wrapper. A JSON object or array nested 4000–5000 levels deep causes JSON.stringify to exceed V8's call stack, throwing RangeError: Maximum call stack size exceeded synchronously. The synchronous throw propagates through the Express error middleware openAPIValidationMiddleware in src/lib/routes/controller.ts, which has no error handler. The Node.js process registers only unhandledRejection, not uncaughtException, so the synchronous error terminates the process with exit(1). The vulnerability is route-independent, affecting all OpenAPI-validated endpoints including the anonymous POST /edge/validate and POST /edge/issue-token. Patched versions are 7.5.2, 7.6.5, and 8.0.2.

Affected products

Unleash unleash-server < 7.5.2, >= 7.6.0 and < 7.6.5, >= 8.0.0 and < 8.0.2

Identifiers

CVE-2026-63462
GHSA-r5pq-6chh-j3xp

Timeline

2026-08-21: disclosed: Advisory published on GitHub Advisory Database
2026-07-01: patched: Patches released as v7.5.2, v7.6.5, and v8.0.2

References

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