CVE-2021-22963
URL Redirection to Untrusted Site ('Open Redirect') in fastify-static
A redirect vulnerability in the fastify-static module version < 4.2.4 allows remote attackers to redirect users to arbitrary websites via a double slash // followed by a domain: http://localhost:3000//google.com/%2e%2e.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
- None
Exploit likelihood
What each source reports
NVD Score used
A redirect vulnerability in the fastify-static module version < 4.2.4 allows remote attackers to redirect users to arbitrary websites via a double slash // followed by a domain: http://localhost:3000//google.com/%2e%2e.The issue shows up on all the fastify-static applications that set redirect: true option. By default, it is false.
- Record
CVE-2021-22963- CVSS 3.1
- 6.1 Medium
CVSS:3.1/AV:N/AC:L/PR:N/UI:R/S:C/C:L/I:L/A:N - CVSS 2.0
- 5.8 Medium
AV:N/AC:M/Au:N/C:P/I:P/A:N - Weakness
- CWE-601
- Updated
- 2026-11-02
CVE List No score
A redirect vulnerability in the fastify-static module version < 4.2.4 allows remote attackers to redirect users to arbitrary websites via a double slash // followed by a domain: http://localhost:3000//google.com/%2e%2e.The issue shows up on all the fastify-static applications that set redirect: true option. By default, it is false.
- Record
CVE-2021-22963- Weakness
- CWE-601
- Updated
- 2026-11-02
EUVDEUVD-2021-2234 No score
A redirect vulnerability in the fastify-static module version < 4.2.4 allows remote attackers to redirect users to arbitrary websites via a double slash // followed by a domain: http://localhost:3000//google.com/%2e%2e.The issue shows up on all the fastify-static applications that set redirect: true option. By default, it is false.
- Record
EUVD-2021-2234- Updated
- 2026-11-03
GitHub AdvisoriesGHSA-p6vg-p826-qp3v
URL Redirection to Untrusted Site ('Open Redirect') in fastify-static
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//google.com/%2e%2e.
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-p6vg-p826-qp3v- CVSS 3.1
- 6.1 Medium
CVSS:3.1/AV:N/AC:L/PR:N/UI:R/S:C/C:L/I:L/A:N - Weakness
- CWE-601
- Updated
- 2026-11-02
OSV
A redirect vulnerability in the fastify-static module version < 4.2.4 allows remote attackers to redirect users to arbitrary websites via a double slash // followed by a domain: http://localhost:3000//google.com/%2e%2e.The issue shows up on all the fastify-static applications that set redirect: true option. By default, it is false.
- Record
CVE-2021-22963- CVSS 3.1
- 6.1 Medium
CVSS:3.1/AV:N/AC:L/PR:N/UI:R/S:C/C:L/I:L/A:N - Updated
- 2026-11-02
OSVGHSA-p6vg-p826-qp3v
URL Redirection to Untrusted Site ('Open Redirect') in fastify-static
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//google.com/%2e%2e.
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-p6vg-p826-qp3v- CVSS 3.1
- 6.1 Medium
CVSS:3.1/AV:N/AC:L/PR:N/UI:R/S:C/C:L/I:L/A:N - Weakness
- CWE-601
- Updated
- 2026-11-02
Affected products
Affected packages
| Package | Affected | Fixed |
|---|---|---|
fastify-staticnpm |
before 4.2.4 | 4.2.4 |
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-2021-22963 is a medium vulnerability (CVSS 6.1) in Fastify Fastify-static, published October 5, 2021. No source lists public exploit code. EPSS puts the chance of exploitation in the next 30 days at 1.17%, the 67th percentile. Fixed in fastify-static 4.2.4.