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CVE-2021-22881

78
FAUCET Score

CVE-2021-22881 is an open redirect vulnerability in the Host Authorization middleware of Action Pack, affecting Ruby on Rails versions prior to 6.1.2.1 and 6.0.3.5, as well as related Fedora projects. This flaw allows attackers to redirect users to malicious websites via specially crafted Host headers when allowed hosts are configured with a leading dot. With a CVSS score of 6.1 (Medium), exploitation requires no privileges but relies on user interaction, potentially leading to limited confidentiality and integrity impacts. While there is no evidence of active exploitation or Metasploit modules, a Nuclei template exists, and the vulnerability has received minimal community attention or media coverage.

Impacted Technologies

VendorProductVersion(s)CPE
>= 6.0.0, < 6.0.3.5CPE matchmatch criteria
cpe:2.3:a:rubyonrails:rails:*:*:*:*:*:*:*:*
>= 6.1.0, < 6.1.2.1CPE matchmatch criteria
cpe:2.3:a:rubyonrails:rails:*:*:*:*:*:*:*:*
33CPE matchmatch criteria
cpe:2.3:o:fedoraproject:fedora:33:*:*:*:*:*:*:*

CVSS Data

CVSS version used by this source: 3.1

6.1MEDIUM

CVSS:3.1/AV:N/AC:L/PR:N/UI:R/S:C/C:L/I:L/A:N

Attack Vector
NETWORK
Attack Complexity
LOW
Privileges Required
NONE
User Interaction
REQUIRED
Scope
CHANGED
Confidentiality Impact
LOW
Integrity Impact
LOW
Availability Impact
NONE
Exploitability Score
2.8
Impact Score
2.7
CvssVersion
3.1

Exploit Intelligence

EPSS Score
87.30%
Probability of exploitation in next 30 days
EPSS Percentile
99.7%
Percentile rank of EPSS score among Peer Group
As of 2026-07-27
Model: v2026.06.15
Nuclei: CVE-2021-22881 · Jan 21, 2026
This CVE's current EPSS score of 0.8730 is in the 100th percentile among its peer group of 26,234 CVEs.

Social Chatter

The average CVE in this peer group has 0.0 Twitter, 0.0 Reddit, 0.1 Bluesky, 0.0 Mastodon, and 0.1 GitHub mentions.

Media Mentions

No media coverage found for this CVE.

The average CVE in this peer group has 0.1 InfoSec Media, 0.0 Vendor Blog, and 0.0 Security Researcher mentions.

Remediation

Patch Available

Vendor Patches (8)

arubapatch availablevia llm_extracted
Fixed in: 5.2.4.5, 6.0.3.5, 6.1.2.1
View patch
boidcmspatch availablevia llm_extracted
Fixed in: 5.2.4.5,6.0.3.5,6.1.2.1
View patch
libvipspatch availablevia llm_extracted
Fixed in: 5.2.4.5, 6.0.3.5, 6.1.2.1
View patch
markusprojectpatch availablevia llm_extracted
Fixed in: 5.2.4.5, 6.0.3.5, 6.1.2.1
View patch
prometheuspatch availablevia llm_extracted
Fixed in: 5.2.4.5, 6.0.3.5, 6.1.2.1
View patch
rubygemspatch availablevia ghsa
Product: actionpackFixed in: 6.1.2.1
rubygemspatch availablevia ghsa
Product: actionpackFixed in: 6.0.3.5
redhatend of lifevia redhat_api
Product: CloudForms Management Engine 5Fixed in: cfme-gemset

Vendor Advisories (7)

rubygemsGHSA-8877-prq4-9xfwmedium

Actionpack Open Redirect Vulnerability

Mar 2, 2021
redhatCVE-2021-22881Moderate

rubygem-actionpack: open redirect vulnerability may lead to confidentiality and integrity compromise

Feb 11, 2021
aruballm-aruba-4ee1556ef6fe52d8

Rails 5.2.4.5, 6.0.3.5 and 6.1.2.1 have been released

Feb 10, 2021
prometheusllm-prometheus-1b8ba84f9f39fe9d

Rails 5.2.4.5, 6.0.3.5 and 6.1.2.1 have been released

Feb 10, 2021
boidcmsllm-boidcms-d25967740c148e67HIGH

Rails 5.2.4.5, 6.0.3.5 and 6.1.2.1 have been released

Feb 10, 2021
libvipsllm-libvips-2f88a88f962c74a4

Rails 5.2.4.5, 6.0.3.5 and 6.1.2.1 have been released

Feb 10, 2021
markusprojectllm-markusproject-5bd674f1ecc483e9

Rails 5.2.4.5, 6.0.3.5 and 6.1.2.1 have been released

Feb 10, 2021

References

benjamin-bouchet.com / cve-2021-22881-faille-de-securite-dans-le-middleware-hostauthorization
PatchThird Party Advisory
discuss.rubyonrails.org / t/cve-2021-22881-possible-open-redirect-in-host-authorization-middleware/77130
MitigationPatchVendor Advisory
hackerone.com / reports/1047447
ExploitPatchThird Party Advisory
lists.fedoraproject.org / archives/list/package-announce%40lists.fedoraproject.org/message/XQ3NS4IBYE2I3MVMGAHFZBZBIZGHXHT3
openwall.com / lists/oss-security/2021/05/05/2
Mailing ListMitigationThird Party Advisory
openwall.com / lists/oss-security/2021/08/20/1
Mailing ListMitigationThird Party Advisory
openwall.com / lists/oss-security/2021/12/14/5
ExploitMailing ListPatch