NVD / CVE Program· CNA openjs

CVE-2026-84469: fastify vulnerable to request validation bypass via skipped boolean false schemas

Noroxi assessment

Priority: Monitor (action score 30/100)

The sources we track (CISA KEV, Exploit-DB, Metasploit, Nuclei, GitHub) show no public exploit code or exploitation in the wild.
Probability of exploitation in the next 30 days: 0.49% (FIRST EPSS).
Anyone who can reach it over the internet can trigger it. No account or password is required. No user action is required. No special conditions are required; it is repeatable.
According to CISA the attack is automatable: targets can be found by mass scanning.
Fixed version: fastify fastify 5.12.2.

Low priority for now. Upgrade to fastify fastify 5.12.2 or later.

Generated automatically from the record's data: CVSS (NVD and CNA), CISA KEV and SSVC, FIRST EPSS, exploit sources, fixed versions. How we calculate it

Primary sources: NVD · CVE.org · FIRST EPSS

fastify versions before 5.12.2 decide whether to compile a request schema based on JavaScript truthiness, but JSON Schema Draft 7 defines the boolean false as a valid schema that rejects every instance. When an application assigns false to a route's body, querystring, params, or headers schema to deny all input, fastify treats it as a missing schema, compiles no validator, and runs the route handler on any request. An unauthenticated remote client can therefore reach a handler that a valid deny-all schema was intended to make unreachable, a complete validation bypass that can lead to unauthorized state changes or execution of disabled operations. Users should upgrade to fastify 5.12.2 or later.

HighCVSS 7.5 · v3.1—No exploit Fix available

Pre-auth

Published: Sep 4, 2026
Updated: Sep 15, 2026
EPSS: 0.4% · 42th percentile
CWE: CWE-20

Report tools

JSON

Action score

Monitor

Low priority for now.

CVSS: 30 / 40 · 7.5 / 10
CISA KEV: 0 / 30 · Not listed
EPSS: 0 / 30 · 0.4%

CISA SSVC decision

Exploitation: none
Automatable: yes
Technical impact: partial

Vulnrichment: CISA's decision-tree inputs.

CNA vs NVD score

NVD: —
CNA · openjs: 7.5; NVD has not scored this yet; the score shown is the CNA’s.

The score given by the assigning authority versus NVD’s independent score. A gap means the severity is contested.

Get told when this record changes

Not in KEV: no record of exploitation in the wild
No public exploit code on record
A fix has been released

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Noroxi analysis

What does it mean in your environment?

The assessment above is generated automatically from the record's data; it doesn't know your environment. Our team verifies on your systems whether this vulnerability is actually exploitable and which mitigation is enough.

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Affected systems

Is your version affected?

Pick the product and type the version you run. It's compared with this record's version ranges in your browser; the version isn't sent anywhere.

Vendor	Product	CPE
fastify	fastify	cpe:2.3:a:fastify:fastify

Affected versions

NVD version ranges (for catalog products). Add the product to your stack with a version and matching uses these.

fastify fastifybefore 5.12.2

Versions reported by the vendor

Affected version ranges reported by the assigning authority (openjs). Independent of NVD's CPE analysis and usually ahead of it.

fastify fastify
- 5.12.2not affected
- before 5.12.2affected · semver

Package-level exposure

OSV and GitHub Advisory data: ecosystem, package and range. SBOM matching uses this table.

Ecosystem	Package	Affected range	Fix
npm	fastify	before 5.12.2	5.12.2

Same product

fastify: all records

Other highest-scoring records for the same primary product.

CVE-2022-39288Denial of service in Fastify via Content-Type header
48Plan
CVE-2022-41919Fastify vulnerable to Cross-Site Request Forgery (CSRF) attack via incorrect content type
35Monitor
CVE-2026-84504fastify vulnerable to request body replacement via an async validation result collision
32Monitor

Published before and after this one in the same product

← EarlierCVE-2026-18504Aug 18, 2026 · fastify vulnerable to schema validation bypass via root primitive coercion mismatch
21Monitor
← EarlierCVE-2026-76169Sep 4, 2026 · fastify vulnerable to authentication bypass via malformed URLs reaching encapsulated not-found handlers
30Monitor
Later →CVE-2026-84428Sep 4, 2026 · fastify vulnerable to header validation bypass via incomplete schema case normalization
30Monitor

Remediation

Which version to upgrade to

Fix versions compiled from the vendor, package registries and Microsoft. Verify the vendor's note before upgrading.

Product / package	Fixed version	Source
fastify fastify	5.12.2	Vendor (CNA)
npm:fastify	5.12.2	Package registry (OSV)

Exploit status

No known public exploit

No public exploit has been observed yet. That doesn't mean you're safe, only that the bar is a little higher.

Research context

For pentesters and researchers: attack profile, score disagreement, timeline, patch commits, credits, variant and chain candidates, bug bounty scope. All derived from existing data; no exploit code.

Timeline

From publication to today: proof of concept, Metasploit module, CISA KEV and fix record. Dates are as reported by the sources.

No dated events beyond publication.

EPSS, last 120 days

FIRST EPSS daily score; only changes of 0.01 or more are recorded (step chart).

Patch and commit links

Commit, PR and diff links among the references. A starting point for patch-diffing and variant hunting; fixes, not exploits.

No commit or PR link among the references.

Credits

All researchers

Finders, reporters and analysts named in the CNA record. Click a name for that researcher’s other records.

schecthellraiser606reporter
mcollinaremediation developer
UlisesGasconremediation developer
climba03003remediation reviewer

Variant candidates

Same product, same weakness class, within 18 months. If the patch missed the root cause, the sibling bug is here.

CVE-2026-845040 days apartfastify vulnerable to request body replacement via an async validation result collision
32Monitor
CVE-2026-1850417 days apartfastify vulnerable to schema validation bypass via root primitive coercion mismatch
21Monitor

Chain candidates

An authentication bypass and a privilege-requiring bug in the same product, published close together: combined they may become an unauthenticated path.

—

Bug bounty scope

No known public program.

Source: bounty-targets-data (public HackerOne, Bugcrowd, Intigriti, YesWeHack listings).

Technical details

Attack conditions

Anyone who can reach it over the internet can trigger it.
No account or password is required.
No user action is required.
No special conditions are required; it is repeatable.

If successful

Confidentiality: none
Integrity: high · data or configuration can be modified
Availability: none

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

Weakness class (CWE)

CWE-20 · Improper Input Validation

CVSS vector

CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:N/I:H/A:N

nvd-secondary

Attack context

MITRE CAPEC attack patterns and ATT&CK techniques for this weakness class (CWE). A starting point for detection rules and threat hunting.

Attack patterns (CAPEC)

ATT&CK techniques

Change log

Fix✗ → ✓Sep 28, 2026, 10:08 PM UTC

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References

cna.openjsf.org/security-advisories.html

Show all references (1 more)

github.com/fastify/fastify/security/advisories/GHSA-hwr6-493r-vm6h

Vendor advisories and official records. Exploit/PoC links are deliberately left out.

All records