How severe is CVE-2022-39386?

CVE-2022-39386 has a CVSS score of 7.5/10, rated HIGH. Immediate patching is strongly recommended.

Which packages are affected by CVE-2022-39386?

CVE-2022-39386 affects the following packages: @fastify/websocket (npm), @fastify/websocket (npm), fastify-websocket (npm). Ecosystems affected: npm.

How do I fix CVE-2022-39386?

Update @fastify/websocket to 5.0.1 or later, then make sure no transitive (indirect) dependency still pins the vulnerable range — O3 confirms CVE-2022-39386 is resolved across your whole dependency graph.

How do I detect CVE-2022-39386 in my npm dependencies?

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

How do I mitigate CVE-2022-39386 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 CVE-2022-39386 actively exploited in the wild?

No public exploit code has been indexed for CVE-2022-39386 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 CVE-2022-39386?

CVE-2022-39386 has an EPSS (Exploit Prediction Scoring System) score of 0.8%, placing it in the 56th 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 CVE-2022-39386?

CVE-2022-39386 is classified as CWE-248 (CWE-248). This weakness type describe the underlying flaw category, which helps determine the potential impact and the right class of mitigation.

When was CVE-2022-39386 published, and has it been updated?

CVE-2022-39386 was published on November 8, 2022 and was last updated on October 28, 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

HIGH severity

CVE-2022-39386 — @fastify/websocket

HIGHFix: fastify/fastify-websocket#228

CVE-2022-39386 is a high-severity (CVSS 7.5) CWE-248 vulnerability in @fastify/websocket. A fix is available for @fastify/websocket — see the affected versions and patch details below.

fastify-websocket vulnerable to uncaught exception via crash on malformed packet

Also known asGHSA-4pcg-wr6c-h9cq

Published

Nov 8, 2022

Updated

Oct 28, 2026

Affected

3 pkgs

Patched

2 / 3

Exploits

None indexed

Exploitation data as of Oct 23, 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 CVE-2022-39386.

EPSS Exploitation Probability

via FIRST.org ↗

0.8%probability of exploitation in next 30 days

Lower Risk+0.02%

Lower risk than most CVEs56th percentile — riskier than 56% 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

3 pkgs 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.

656other npm packages depend on this — each one inherits the vulnerability until it's patched upstream

@fastify/websocketnpm

1.7Mdownloads / week

fastify-websocketnpm

3Kdownloads / week

Description

Impact

Any application using @fastify/websocket could crash if a specific, malformed packet is sent.

All versions of fastify-websocket are also impacted. That module is deprecated, so it will not be patched.

Patches

This has been patched in v7.1.1 (fastify v4) and v5.0.1 (fastify v3).

Workarounds

No known workaround is available. However, it should be possible to attach the error handler manually. The recommended path is upgrading to the patched versions.

Credits

marcolanaro for finding and patching this vulnerability

For more information

If you have any questions or comments about this advisory:

Open an issue in @fastify/websocket
Email us at [email protected]

Affected Packages

3 total 2 fixed

Ecosystem	Package	Vulnerable range	Fix
📦npm	`@fastify/websocket`	≥ 5.0.0&&< 5.0.1	5.0.1`npm install @fastify/websocket@5.0.1`
📦npm	`@fastify/websocket`	≥ 6.0.0&&< 7.1.1	7.1.1`npm install @fastify/websocket@7.1.1`
📦npm	`fastify-websocket`	all versions	No fix

Affected Products

1 product · 2 configurations

Application

websocketfastify

≥ 6.0.0 && < 7.1.1

1 version

5.0.0

Detection & mitigation playbook

Open-source dependency

Detect
Scan your dependency tree (package-lock.json, pnpm-lock.yaml, requirements.txt, go.sum, etc.) for @fastify/websocket, including transitive dependencies — a direct dependency you never call can still pull in a vulnerable version.
Fix
Update @fastify/websocket to 5.0.1 or later, then make sure no transitive (indirect) dependency still pins the vulnerable range — O3 confirms CVE-2022-39386 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.

Frequently Asked Questions

### Impact Any application using @fastify/websocket could crash if a specific, malformed packet is sent. All versions of fastify-websocket are also impacted. That module is deprecated, so it will not be patched. ### Patches This has been patched in v7.1.1 (fastify v4) and v5.0.1 (fastify v3). ### Workarounds No known workaround is available. However, it should be possible to attach the error handler manually. The recommended path is upgrading to the patched versions. ## Credits [marcolanaro](https://github.com/marcolanaro) for finding and patching this vulnerability ### For more info