CVE-2021-22964Public exploitNetwork attack vector

Open redirect and crash via unsafe URL parsing

Published Oct 14, 2021 · Updated Aug 3, 2024

Open redirect and denial of service in Fastify @fastify/static 4.2.4 through 4.4.0 allow remote attackers to redirect Firefox users or crash servers. The getRedirectUrl function passes raw request URLs to the URL constructor and uses the parsed pathname in a 301 response without rejecting protocol-relative or backslash-prefixed forms; malformed inputs also raise uncaught exceptions. Only applications with nondefault redirect: true are exposed, and open-redirection impact requires a Firefox user to follow the crafted URL.

CVSS severity8.8
High
EPSS probability1.02%
Next 30 days · Sep 16, 2026
Known exploitationUnconfirmed
Based on sourced intelligence
Hinoki checkNot available
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Summary

What happened

Open redirect and denial of service in Fastify @fastify/static 4.2.4 through 4.4.0 allow remote attackers to redirect Firefox users or crash servers. The getRedirectUrl function passes raw request URLs to the URL constructor and uses the parsed pathname in a 301 response without rejecting protocol-relative or backslash-prefixed forms; malformed inputs also raise uncaught exceptions. Only applications with nondefault redirect: true are exposed, and open-redirection impact requires a Firefox user to follow the crafted URL.

The record

CVE
CVE-2021-22964
Published
Oct 14, 2021
Updated
Aug 3, 2024
Vendor
Fastify
Product
@fastify/static
Classifications
CWE-248, CWE-601
Attack vector
network
Privileges
unauthenticated

Timeline

How it unfolded

  1. Oct 14, 2021CVE publishedPublication date reported by the CVE source.
  2. Aug 3, 2024Record updatedLatest update available in the CVE record.

Exploitability

Present is not the same as exploitable

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Is a vulnerable build present?

Compare these published version ranges with your installed build and any vendor patches.

  1. Affected versionversion=Affected >= v4.2.4, Fixed v4.4.1

What conditions does exploitation require?

Attack vectornetwork
Required privilegesunauthenticated

What is affected?

Fastify · @fastify/staticversion=Affected >= v4.2.4, Fixed v4.4.1

Published CVSS scores

6.8NIST NVDAV:N/AC:M/Au:N/C:P/I:P/A:P
8.8GitHub Advisory DatabaseCVSS:3.1/AV:N/AC:L/PR:N/UI:R/S:C/C:L/I:L/A:H
8.8NIST NVDCVSS:3.1/AV:N/AC:L/PR:N/UI:R/S:C/C:L/I:L/A:H

CVSS describes severity. EPSS estimates exploitation probability.

Attacks

What attackers are doing with it

Daily unique IPs observed by Shadowserver honeypots for known exploited vulnerabilities (KEVs). Missing observations do not establish an absence of attacks.

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No observations available

Sep 10, 2026Sep 16, 2026
Latest reporting daySep 16, 2026
Latest daily unique IPsUnavailable
Prior 30-day averageUnavailable
SourceShadowserver honeypots (KEV)
Vectornetwork
Privilegesunauthenticated
Known exploitationUnconfirmed
Public exploitPublished

Weakness, pattern, technique

CWE-248Uncaught Exception
CWE-601URL Redirection to Untrusted Site ('Open Redirect')

Public exploit references

Labels summarize the accepted research assessment. They do not indicate a test against your environment.

Technologies

Your stack

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Your stack

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