How severe is CVE-2021-22881?

CVE-2021-22881 has a CVSS 3.x base score of 6.1, rated medium 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 none.

Is CVE-2021-22881 being actively exploited?

It is not currently listed in CISA's KEV catalog. Its EPSS exploit-prediction score is 87% (100th percentile), an estimate of the probability of exploitation in the next 30 days.

What products are affected by CVE-2021-22881?

CVE-2021-22881 primarily affects Rubyonrails Rails. In total, 2 product configurations (CPEs) are listed as vulnerable; see the affected-products list for the exact versions.

How do I fix CVE-2021-22881?

Review the linked vendor and NVD advisories for patched versions and mitigations, then upgrade or apply the recommended workaround.

When was CVE-2021-22881 published?

CVE-2021-22881 was published on 2021-02-11 and last updated on 2026-06-17.

CVE-2021-22881

CVE-2021-22881 is a medium-severity vulnerability in Rubyonrails Rails with a CVSS 3.x base score of 6.1. Its EPSS exploit-prediction score of 87% places it in the 100th percentile, indicating an elevated likelihood of exploitation. The underlying weakness is classified as CWE-601.

Key facts

Severity: Medium (CVSS 3.x base score 6.1)
CVSS v2: 5.8
EPSS exploit prediction: 87% (100th percentile)
Actively exploited: Not listed in CISA KEV
Weakness: CWE-601
Affected product: Rubyonrails Rails
Published: 2021-02-11
Last modified: 2026-06-17

Description

The Host Authorization middleware in Action Pack before 6.1.2.1, 6.0.3.5 suffers from an open redirect vulnerability. Specially crafted `Host` headers in combination with certain "allowed host" formats can cause the Host Authorization middleware in Action Pack to redirect users to a malicious website. Impacted applications will have allowed hosts with a leading dot. When an allowed host contains a leading dot, a specially crafted `Host` header can be used to redirect to a malicious website.

Frequently asked questions

What is CVE-2021-22881?: The Host Authorization middleware in Action Pack before 6.1.2.1, 6.0.3.5 suffers from an open redirect vulnerability. Specially crafted `Host` headers in combination with certain "allowed host" formats can cause the Host Authorization middleware in Action Pack to redirect users to a malicious website. Impacted applications will have allowed hosts with a leading dot. When an allowed host contains a leading dot, a specially crafted `Host` header can be used to redirect to a malicious website.
How severe is CVE-2021-22881?: CVE-2021-22881 has a CVSS 3.x base score of 6.1, rated medium 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 none.
Is CVE-2021-22881 being actively exploited?: It is not currently listed in CISA's KEV catalog. Its EPSS exploit-prediction score is 87% (100th percentile), an estimate of the probability of exploitation in the next 30 days.
What products are affected by CVE-2021-22881?: CVE-2021-22881 primarily affects Rubyonrails Rails. In total, 2 product configurations (CPEs) are listed as vulnerable; see the affected-products list for the exact versions.
How do I fix CVE-2021-22881?: Review the linked vendor and NVD advisories for patched versions and mitigations, then upgrade or apply the recommended workaround.
When was CVE-2021-22881 published?: CVE-2021-22881 was published on 2021-02-11 and last updated on 2026-06-17.

References

Affected products (2)

cpe:2.3:a:rubyonrails:rails:*:*:*:*:*:*:*:*
cpe:2.3:o:fedoraproject:fedora:33:*:*:*:*:*:*:*

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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…
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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…
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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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