CVE-2021-22964
DOS and Open Redirect with user input
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
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 High
CVSS:3.1/AV:N/AC:L/PR:N/UI:R/S:C/C:L/I:L/A:H - CVSS 2.0
- 6.8 Medium
AV: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
- Bug founder: drstrnegth
- hackerone Report
For more information
If you have any questions or comments about this advisory:
- Open an issue in fastify-static
- Contact the security team
- Record
GHSA-pgh6-m65r-2rhq- CVSS 3.1
- 8.8 High
CVSS: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 High
CVSS: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
- Bug founder: drstrnegth
- hackerone Report
For more information
If you have any questions or comments about this advisory:
- Open an issue in fastify-static
- Contact the security team
- Record
GHSA-pgh6-m65r-2rhq- CVSS 3.1
- 8.8 High
CVSS: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
| Package | Affected | Fixed |
|---|---|---|
fastify-staticnpm |
4.2.4 up to 4.4.1 | 4.4.1 |
History
| Recorded | Changed | Sources |
|---|---|---|
| aliases | EUVD | |
| first indexed | CVE 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.