CVE-2021-23435: Open Redirect

Severity: medium (CVSS 6.1 v3.1)
Exploited in the wild: not listed in CISA KEV
EPSS: 0.7% probability of exploitation in the next 30 days
Public exploit or detection template: none known
Published: 2021-09-12 · updated 2026-06-17
Weakness: CWE-601

Description

This affects the package clearance before 2.5.0. The vulnerability can be possible when users are able to set the value of session[:return_to]. If the value used for return_to contains multiple leading slashes (/////example.com) the user ends up being redirected to the external domain that comes after the slashes (http://example.com).

Affected products

clearance: before 2.5.0 — fixed in 2.5.0

How to fix

Upgrade to a fixed version: clearance 2.5.0. Check the vendor advisory for mitigations.

References

https://github.com/thoughtbot/clearance/pull/945
https://snyk.io/vuln/SNYK-RUBY-CLEARANCE-1577284
https://github.com/thoughtbot/clearance/pull/945
https://snyk.io/vuln/SNYK-RUBY-CLEARANCE-1577284

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