Go to homepageCyberStrike

Menu

Star on GitHub · 3.4k
Sign inDownload

CVE-2026-84504

8.1 · HIGH

fastify versions before 5.12.2 treat the object resolved by a successful Ajv async validator as the value result protocol used by custom validator compilers.

Published Sep 4, 2026fastifyCWE-20EPSS 0.43%

Overview

CVE-2026-84504 is a high-severity vulnerability affecting fastify fastify. It was published on September 4, 2026 and has a CVSS 3.1 base score of 8.1 (HIGH).

This vulnerability has a CVSS 3.1 base score of 8.1, rated HIGH. It can be exploited remotely over the network. Some level of privileges is required for exploitation.

Technical description

fastify versions before 5.12.2 treat the object resolved by a successful Ajv async validator as the value result protocol used by custom validator compilers. If a request that passes its route schema contains a property named value at the root, fastify replaces the entire request body with that property's value before the handler runs, so the handler receives a different object than the one that satisfied the schema. An authenticated low-privilege caller can use this to make nested data replace the validated body and trigger an operation the route schema did not authorize, leading to unauthorized state changes and data disclosure. Users should upgrade to fastify 5.12.2 or later.

Remediation

Check the references section for vendor advisories and patches from fastify. Update fastify to the latest patched version. If immediate patching is not possible, review the CVSS vector to understand the attack surface and apply compensating controls such as network segmentation or access restrictions.

Affected products

VendorProductVersionsStatus
fastifyfastify>= 0, < 5.12.2Affected

References

Refcna.openjsf.org/security-advisories.htmlGitHubgithub.com/fastify/fastify/security/advisories/GHSA-667r-xxjv-c9mm

How CyberStrike helps

Frequently asked questions

What is CVE-2026-84504?

CVE-2026-84504 is a high-severity vulnerability affecting fastify fastify. It was published on September 4, 2026 and has a CVSS 3.1 base score of 8.1 (HIGH).

How severe is CVE-2026-84504?

This vulnerability has a CVSS 3.1 base score of 8.1, rated HIGH. It can be exploited remotely over the network. Some level of privileges is required for exploitation.

How do I fix or remediate CVE-2026-84504?

Check the references section for vendor advisories and patches from fastify. Update fastify to the latest patched version. If immediate patching is not possible, review the CVSS vector to understand the attack surface and apply compensating controls such as network segmentation or access restrictions.

How can CyberStrike help with CVE-2026-84504?

CyberStrike is an open-source, AI-augmented pentesting engine. Rather than flag a version number, it tests whether an issue like CVE-2026-84504 is actually reachable in your own applications and APIs, then verifies each finding before reporting it. That tells you if the weakness is a real, exploitable risk in your environment or a false positive you can safely deprioritize.

Related HIGH CVEs from 2026

View all
Browse by year2026202520242023202220212020201920182017201620152014201320122011201020092008200720062005200420032002200120001999
Watch the demo →