How severe is CVE-2021-22964?

CVE-2021-22964 has a CVSS 3.x base score of 8.8, rated high severity. It is exploitable over network with low attack complexity, requires no privileges and user interaction. Impact on confidentiality is low, integrity low, and availability high.

Is CVE-2021-22964 being actively exploited?

It is not currently listed in CISA's KEV catalog. Its EPSS exploit-prediction score is 1% (58th percentile), an estimate of the probability of exploitation in the next 30 days.

What products are affected by CVE-2021-22964?

CVE-2021-22964 affects Fastify Fastify-static. See the affected-products list for the exact vulnerable versions.

How do I fix CVE-2021-22964?

Review the linked vendor and NVD advisories for patched versions and mitigations, then upgrade or apply the recommended workaround. Given its high severity, prioritise patching exposed systems.

When was CVE-2021-22964 published?

CVE-2021-22964 was published on 2021-10-14 and last updated on 2026-06-17.

CVE-2021-22964

CVE-2021-22964 is a high-severity vulnerability in Fastify Fastify-static with a CVSS 3.x base score of 8.8. It is not currently listed as actively exploited by CISA, and its EPSS exploit-prediction score is low. The underlying weakness is classified as CWE-601.

Key facts

Severity: High (CVSS 3.x base score 8.8)
CVSS v2: 6.8
EPSS exploit prediction: 1% (58th percentile)
Actively exploited: Not listed in CISA KEV
Weakness: CWE-601
Affected product: Fastify Fastify-static
Published: 2021-10-14
Last modified: 2026-06-17

Description

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`.

Frequently asked questions

What is CVE-2021-22964?: 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`.
How severe is CVE-2021-22964?: CVE-2021-22964 has a CVSS 3.x base score of 8.8, rated high severity. It is exploitable over network with low attack complexity, requires no privileges and user interaction. Impact on confidentiality is low, integrity low, and availability high.
Is CVE-2021-22964 being actively exploited?: It is not currently listed in CISA's KEV catalog. Its EPSS exploit-prediction score is 1% (58th percentile), an estimate of the probability of exploitation in the next 30 days.
What products are affected by CVE-2021-22964?: CVE-2021-22964 affects Fastify Fastify-static. See the affected-products list for the exact vulnerable versions.
How do I fix CVE-2021-22964?: Review the linked vendor and NVD advisories for patched versions and mitigations, then upgrade or apply the recommended workaround. Given its high severity, prioritise patching exposed systems.
When was CVE-2021-22964 published?: CVE-2021-22964 was published on 2021-10-14 and last updated on 2026-06-17.

References

https://hackerone.com/reports/1361804

Affected products (1)

cpe:2.3:a:fastify:fastify-static:*:*:*:*:*:*:*:*

More vulnerabilities in Fastify Fastify-static

CVE-2021-22963 — Medium (CVSS 6.1): A redirect vulnerability in the fastify-static module version < 4.2.4 allows remote attackers to redirect users to…
CVE-2026-6414 — Medium (CVSS 5.9): @fastify/static versions 8.0.0 through 9.1.0 decode percent-encoded path separators (%2F) before filesystem resolution,…
CVE-2026-6410 — Medium (CVSS 5.3): @fastify/static versions 8.0.0 through 9.1.0 allow path traversal when directory listing is enabled via the list…

All CVEs affecting Fastify Fastify-static →

Other CWE-601 (Open Redirect) vulnerabilities

CVE-2018-3774 — Critical (CVSS 10.0): Incorrect parsing in url-parse <1.4.3 returns wrong hostname which leads to multiple vulnerabilities such as SSRF, Open…
CVE-2019-25282 — Critical (CVSS 9.8): V-SOL GPON/EPON OLT Platform v2.03 contains an open redirect vulnerability in the script that allows attackers to…
CVE-2020-36912 — Critical (CVSS 9.8): Plexus anblick Digital Signage Management 3.1.13 contains an open redirect vulnerability in the 'PantallaLogin' script…
CVE-2025-43526 — Critical (CVSS 9.8): This issue was addressed with improved URL validation. This issue is fixed in Safari 26.2, macOS Tahoe 26.2. On a Mac…
CVE-2025-55031 — Critical (CVSS 9.8): Malicious pages could use Firefox for iOS to pass FIDO: links to the OS and trigger the hybrid passkey transport. An…
CVE-2024-22891 — Critical (CVSS 9.8): Nteract v.0.28.0 was discovered to contain a remote code execution (RCE) vulnerability via the Markdown link.

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