How severe is GHSA-573f-x89g-hqp9?

GHSA-573f-x89g-hqp9 has a CVSS score of 5.3/10, rated MEDIUM. Review your exposure and patch according to your risk tolerance.

Which packages are affected by GHSA-573f-x89g-hqp9?

GHSA-573f-x89g-hqp9 affects the following packages: fastify (npm). Ecosystems affected: npm.

How do I fix GHSA-573f-x89g-hqp9?

Update fastify to 5.8.1 or later, then make sure no transitive (indirect) dependency still pins the vulnerable range — O3 confirms GHSA-573f-x89g-hqp9 is resolved across your whole dependency graph.

How do I detect GHSA-573f-x89g-hqp9 in my npm dependencies?

Scan your dependency tree (package-lock.json, pnpm-lock.yaml, requirements.txt, go.sum, etc.) for fastify, including transitive dependencies — a direct dependency you never call can still pull in a vulnerable version.

How do I mitigate GHSA-573f-x89g-hqp9 if there is no patch (or I can't update yet)?

If you can't upgrade right away: gate or disable the affected feature, validate untrusted input at the boundary, and avoid passing attacker-controlled data into the vulnerable path. O3's runtime protection blocks exploitation in production as an interim safeguard until the upgrade lands.

Is GHSA-573f-x89g-hqp9 actively exploited in the wild?

No public exploit code has been indexed for GHSA-573f-x89g-hqp9 yet. This does not mean the vulnerability cannot be exploited — absence of public exploits does not imply safety. Apply the recommended fix and use O3 Security to monitor your exposure.

What is the EPSS score for GHSA-573f-x89g-hqp9?

GHSA-573f-x89g-hqp9 has an EPSS (Exploit Prediction Scoring System) score of 0.4%, placing it in the 33th percentile of all CVEs. EPSS is maintained by FIRST.org and estimates the probability that a vulnerability will be exploited in the wild within the next 30 days. This score indicates relatively lower exploitation probability, though the CVSS severity should still guide your patching priority.

What type of vulnerability is GHSA-573f-x89g-hqp9?

GHSA-573f-x89g-hqp9 is classified as CWE-185 (CWE-185). This weakness type describe the underlying flaw category, which helps determine the potential impact and the right class of mitigation.

When was GHSA-573f-x89g-hqp9 published, and has it been updated?

GHSA-573f-x89g-hqp9 was published on March 5, 2026 and was last updated on July 8, 2026. Advisory data evolves as severity scores, affected ranges, and exploit intelligence are revised — always check the latest version of the advisory before acting.

📦

📦 npm

Not in CISA KEV

MEDIUM severity

Fastify's Missing End Anchor in "subtypeNameReg" Allows Malformed Content-Types to Pass ValidationGHSA-573f-x89g-hqp9

MEDIUMFix: fastify/fastify@67f6c9b

GHSA-573f-x89g-hqp9 is a medium-severity (CVSS 5.3) CWE-185 vulnerability in fastify. A fix is available for fastify — see the affected versions and patch details below.

Also known asCVE-2026-3419

Published

Mar 5, 2026

Updated

Jul 8, 2026

Affected

1 pkg

Patched

1 / 1

Exploits

None indexed

Exploitation data as of Nov 6, 2026 · OSV.dev, NVD, FIRST.org (EPSS)

Exploitation Status

No confirmed exploitation observed yet

CISA assesses this as automatable — exploitation doesn’t require manual, per-target effort, which raises the odds of mass scanning and opportunistic attacks.
CISA’s own triage has not observed active exploitation or public proof-of-concept code for this CVE as of its last assessment.

Exploitation and automatability from CISA’s SSVC triage for GHSA-573f-x89g-hqp9.

EPSS Exploitation Probability

via FIRST.org ↗

0.4%probability of exploitation in next 30 days

Lower Risk0.00%

Lower risk than most CVEs33th percentile — riskier than 33% of all scored CVEsHighest risk

Probability of exploitation in the next 30 days, from FIRST.org EPSS.

How urgent is this, really

Where this sits among everything scored

Real-World Exposure

1 pkg affected

How broadly this vulnerability is actually deployed: weekly install volume shows current usage, and reverse-dependency count shows how many other packages break if it stays unpatched.

6Kother npm packages depend on this — each one inherits the vulnerability until it's patched upstream

fastifynpm

22.3Mdownloads / week

Description

Fastify incorrectly accepts malformed Content-Type headers containing trailing characters after the subtype token, in violation of RFC 9110 §8.3.1. For example, a request sent with Content-Type: application/json garbage passes validation and is processed normally, rather than being rejected with 415 Unsupported Media Type.

When regex-based content-type parsers are in use (a documented Fastify feature), the malformed value is matched against registered parsers using the full string including the trailing garbage. This means a request with an invalid content-type may be routed to and processed by a parser it should never have reached.

Impact

An attacker can send requests with RFC-invalid Content-Type headers that bypass validity checks, reach content-type parser matching, and be processed by the server. Requests that should be rejected at the validation stage are instead handled as if the content-type were valid.

Workarounds

Deploy a WAF rule to protect against this

Fix

The fix is available starting with v5.8.1.

Affected Packages

1 total 1 fixed

Ecosystem	Package	Vulnerable range	Fix
📦npm	`fastify`	≥ 5.7.2&&< 5.8.1	5.8.1`npm install fastify@5.8.1`

Affected Products

1 product · 1 configurations

Application

fastifyfastify

≥ 5.7.2 && < 5.8.1

range

Detection & mitigation playbook

Open-source dependency

Detect
Scan your dependency tree (package-lock.json, pnpm-lock.yaml, requirements.txt, go.sum, etc.) for fastify, including transitive dependencies — a direct dependency you never call can still pull in a vulnerable version.
Fix
Update fastify to 5.8.1 or later, then make sure no transitive (indirect) dependency still pins the vulnerable range — O3 confirms GHSA-573f-x89g-hqp9 is resolved across your whole dependency graph.
Workarounds
If you can't upgrade right away: gate or disable the affected feature, validate untrusted input at the boundary, and avoid passing attacker-controlled data into the vulnerable path. O3's runtime protection blocks exploitation in production as an interim safeguard until the upgrade lands.

Fixing This On Your OS

If you run this on a Linux distribution, patch through your package manager against the distro's own security advisory below — it tracks the exact backported fix for your release, which can ship on a different timeline (and sometimes a different severity) than the upstream project.

Red HatModerate

Workaround published by Red Hat

Mitigation for this issue is either not available or the currently available options do not meet the Red Hat Product Security criteria comprising ease of use and deployment, applicability to widespread installation base or stability.

Source: Red Hat security advisory for GHSA-573f-x89g-hqp9 (CC BY 4.0)

Frequently Asked Questions

# Description Fastify incorrectly accepts malformed `Content-Type` headers containing trailing characters after the subtype token, in violation of [RFC 9110 §8.3.1](https://httpwg.org/specs/rfc9110.html#field.content-type). For example, a request sent with `Content-Type: application/json garbage` passes validation and is processed normally, rather than being rejected with `415 Unsupported Media Type`. When regex-based content-type parsers are in use (a documented Fastify feature), the malformed value is matched against registered parsers using the full string including the trailing garbage.