PatchTheCVECVE-2021-23435: This affects the package clearance before 2.5.0
CVE-2021-23435 is a high-severity flaw (CVSS 7.6) affecting clearance. Below: why it ranks where it does, which versions are affected, what to do, and the exact commands.
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).
Why this priority
- High severity
A fixed release or distro patch exists.
Risk facts
| CVSS score | 7.6 (High) |
| Attack vector | Network (remote) |
| Attack complexity | Low |
| Privileges needed | None |
| User interaction | Required |
| EPSS exploit chance | 0.7% (top 47%) |
| CISA exploited list | No |
| Weakness | CWE-601 |
| Published | 2021-09-12 |
| Last modified | 2026-06-17 |
Last updated 2026-06-17 · Sources: CVE Program, NVD, CISA KEV, EPSS and vendor advisories · How we score
Am I affected?
Timeline
- Published CVE record published
- Updated Record last modified
Scores and fixes here are computed automatically from those and other public sources. Confirm with the vendor advisory before changing production systems.
Quick answers
How do I fix CVE-2021-23435?
clearance: upgrade to 2.5.0. Exact commands for each OS are on this page.
Is CVE-2021-23435 being exploited?
CVE-2021-23435 is not on the CISA Known Exploited Vulnerabilities list at the time of the last update. Check again, as this can change.
What does CVE-2021-23435 affect?
CVE-2021-23435 affects clearance. Severity is high (CVSS 7.6). 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 en
How urgent is CVE-2021-23435?
Priority 40/100. High severity