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CVE-2021-22964

DOS and Open Redirect with user input

8.8 HighFix available

A redirect vulnerability in the fastify-static module version >= 4.2.4 and < 4.4.1 allows remote attackers to redirect Mozilla Firefox users to arbitrary websites via a double slash // followed by a domain: http://localhost:3000//a//youtube.com/%2e%2e%2f%2e%2e.A DOS vulnerability is possible if the URL contains invalid characters curl --path-as-is "http://localhost:3000//^/.."The issue shows up on all the fastify-static applications that set redirect: true option. By default, it is false.

Attack profile

How easy it is to exploit

Attack vector
Network
Complexity
Low
Privileges needed
None
User interaction
Required

What an attacker can affect

Confidentiality
Low
Integrity
Low
Availability
High

Exploit likelihood

1.02%Up 0.5 points since Oct 15, 2021
90%50%10%1%

What each source reports

NVD Score used 8.8

A redirect vulnerability in the fastify-static module version >= 4.2.4 and < 4.4.1 allows remote attackers to redirect Mozilla Firefox users to arbitrary websites via a double slash // followed by a domain: http://localhost:3000//a//youtube.com/%2e%2e%2f%2e%2e.A DOS vulnerability is possible if the URL contains invalid characters curl --path-as-is "http://localhost:3000//^/.."The issue shows up on all the fastify-static applications that set redirect: true option. By default, it is false.

Record
CVE-2021-22964
CVSS 3.1
8.8 HighCVSS:3.1/AV:N/AC:L/PR:N/UI:R/S:C/C:L/I:L/A:H
CVSS 2.0
6.8 MediumAV:N/AC:M/Au:N/C:P/I:P/A:P
Weakness
CWE-400, CWE-601
Updated
2026-11-02
CVE List No score

A redirect vulnerability in the fastify-static module version >= 4.2.4 and < 4.4.1 allows remote attackers to redirect Mozilla Firefox users to arbitrary websites via a double slash // followed by a domain: http://localhost:3000//a//youtube.com/%2e%2e%2f%2e%2e.A DOS vulnerability is possible if the URL contains invalid characters curl --path-as-is "http://localhost:3000//^/.."The issue shows up on all the fastify-static applications that set redirect: true option. By default, it is false.

Record
CVE-2021-22964
Weakness
CWE-400
Updated
2026-11-02
EUVDEUVD-2021-2236 No score

A redirect vulnerability in the fastify-static module version >= 4.2.4 and < 4.4.1 allows remote attackers to redirect Mozilla Firefox users to arbitrary websites via a double slash // followed by a domain: http://localhost:3000//a//youtube.com/%2e%2e%2f%2e%2e.A DOS vulnerability is possible if the URL contains invalid characters curl --path-as-is "http://localhost:3000//^/.."The issue shows up on all the fastify-static applications that set redirect: true option. By default, it is false.

Record
EUVD-2021-2236
Updated
2026-11-03
GitHub AdvisoriesGHSA-pgh6-m65r-2rhq 8.8

DOS and Open Redirect with user input

Impact

A redirect vulnerability in the fastify-static module allows remote attackers to redirect Mozilla Firefox users to arbitrary websites via a double slash // followed by a domain: http://localhost:3000//a//youtube.com/%2e%2e%2f%2e%2e.

A DOS vulnerability is possible if the URL contains invalid characters curl --path-as-is "http://localhost:3000//^/.."

The issue shows up on all the fastify-static applications that set redirect: true option. By default, it is false.

Patches

The issue has been patched in [email protected]

Workarounds

If updating is not an option, you can sanitize the input URLs using the rewriteUrl server option.

References

For more information

If you have any questions or comments about this advisory:

Record
GHSA-pgh6-m65r-2rhq
CVSS 3.1
8.8 HighCVSS:3.1/AV:N/AC:L/PR:N/UI:R/S:C/C:L/I:L/A:H
Weakness
CWE-248, CWE-601
Updated
2026-11-02
OSV 8.8

A redirect vulnerability in the fastify-static module version >= 4.2.4 and < 4.4.1 allows remote attackers to redirect Mozilla Firefox users to arbitrary websites via a double slash // followed by a domain: http://localhost:3000//a//youtube.com/%2e%2e%2f%2e%2e.A DOS vulnerability is possible if the URL contains invalid characters curl --path-as-is "http://localhost:3000//^/.."The issue shows up on all the fastify-static applications that set redirect: true option. By default, it is false.

Record
CVE-2021-22964
CVSS 3.1
8.8 HighCVSS:3.1/AV:N/AC:L/PR:N/UI:R/S:C/C:L/I:L/A:H
Updated
2026-11-02
OSVGHSA-pgh6-m65r-2rhq 8.8

DOS and Open Redirect with user input

Impact

A redirect vulnerability in the fastify-static module allows remote attackers to redirect Mozilla Firefox users to arbitrary websites via a double slash // followed by a domain: http://localhost:3000//a//youtube.com/%2e%2e%2f%2e%2e.

A DOS vulnerability is possible if the URL contains invalid characters curl --path-as-is "http://localhost:3000//^/.."

The issue shows up on all the fastify-static applications that set redirect: true option. By default, it is false.

Patches

The issue has been patched in [email protected]

Workarounds

If updating is not an option, you can sanitize the input URLs using the rewriteUrl server option.

References

For more information

If you have any questions or comments about this advisory:

Record
GHSA-pgh6-m65r-2rhq
CVSS 3.1
8.8 HighCVSS:3.1/AV:N/AC:L/PR:N/UI:R/S:C/C:L/I:L/A:H
Weakness
CWE-248, CWE-601
Updated
2026-11-02

Affected products

Affected packages

Affected packages
PackageAffectedFixed
fastify-static
npm
4.2.4 up to 4.4.1
4.4.1

History

History
RecordedChangedSources
aliasesEUVD
first indexedCVE List, GitHub Advisories, NVD, OSV

Dates are when Every CVE recorded each change. Upstream dates may differ.

In short

CVE-2021-22964 is a high vulnerability (CVSS 8.8) in Fastify Fastify-static, published October 12, 2021. No source lists public exploit code. EPSS puts the chance of exploitation in the next 30 days at 1.02%, the 63rd percentile. Fixed in fastify-static 4.4.1.

References

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