CVE-2021-22942Network attack vector

User redirection via case-sensitive forwarded-host validation

Published Oct 18, 2021 · Updated Aug 3, 2024

Open redirect in Action Pack 6.0.0 through 6.0.4 and 6.1.0 through 6.1.4 allows remote attackers to redirect users via crafted headers. HostAuthorization#authorized? treats a mixed-case X-Forwarded-Host value that misses its case-sensitive hostname match as absent, bypassing the allowed-host check. Exploitation requires an application with a leading-dot allowed host and user interaction with the resulting redirect.

CVSS severity6.1
Medium
EPSS probability1.70%
Next 30 days · Sep 16, 2026
Known exploitationUnconfirmed
Based on sourced intelligence
Hinoki checkNot available
Coverage for this vulnerability

See if you're affected

Explore vulnerability checks for your environment with Hinoki.

Book a demo

Summary

What happened

Open redirect in Action Pack 6.0.0 through 6.0.4 and 6.1.0 through 6.1.4 allows remote attackers to redirect users via crafted headers. HostAuthorization#authorized? treats a mixed-case X-Forwarded-Host value that misses its case-sensitive hostname match as absent, bypassing the allowed-host check. Exploitation requires an application with a leading-dot allowed host and user interaction with the resulting redirect.

The record

CVE
CVE-2021-22942
Published
Oct 18, 2021
Updated
Aug 3, 2024
Vendor
Rails
Product
Action Pack
Classifications
CWE-601, T1190
Attack vector
network
Privileges
unauthenticated

Timeline

How it unfolded

  1. Oct 18, 2021CVE publishedPublication date reported by the CVE source.
  2. Aug 3, 2024Record updatedLatest update available in the CVE record.

Exploitability

Present is not the same as exploitable

Compare your product and version with the public record. A matching version still requires validation against your environment.

Is a vulnerable build present?

Compare these published version ranges with your installed build and any vendor patches.

  1. Affected versionversion=6.1.4.1, 6.0.4.1

What conditions does exploitation require?

Attack vectornetwork
Required privilegesunauthenticated

What is affected?

Rails · Action Packversion=6.1.4.1, 6.0.4.1

Published CVSS scores

6.1NIST NVDCVSS:3.1/AV:N/AC:L/PR:N/UI:R/S:C/C:L/I:L/A:N
5.8NIST NVDAV:N/AC:M/Au:N/C:P/I:P/A:N

CVSS describes severity. EPSS estimates exploitation probability.

Attacks

What attackers are doing with it

Daily unique IPs observed by Shadowserver honeypots for known exploited vulnerabilities (KEVs). Missing observations do not establish an absence of attacks.

Daily unique IPsNo honeypot observations are available for this CVE in the selected window.

No observations available

Sep 10, 2026Sep 16, 2026
Latest reporting daySep 16, 2026
Latest daily unique IPsUnavailable
Prior 30-day averageUnavailable
SourceShadowserver honeypots (KEV)
Vectornetwork
Privilegesunauthenticated
Known exploitationUnconfirmed
Public exploitUnconfirmed

Weakness, pattern, technique

CWE-601URL Redirection to Untrusted Site ('Open Redirect')
T1190Exploit Public-Facing Application

Public exploit references

No public exploit references are available in this record.

Labels summarize the accepted research assessment. They do not indicate a test against your environment.

Technologies

Your stack

See the directory against your own environment.

Your stack

Check the software in your environment

Book a demo to see how Hinoki identifies affected software and validates exploitability in your environment.

Book a demo