CVE-2018-16471: There is a possible XSS vulnerability in Rack before 2.0.6 and 1.6.11. Carefully crafted requests can impact the data returned by the `scheme` method ...

Description

There is a possible XSS vulnerability in Rack before 2.0.6 and 1.6.11. Carefully crafted requests can impact the data returned by the `scheme` method on `Rack::Request`. Applications that expect the scheme to be limited to 'http' or 'https' and do not escape the return value could be vulnerable to an XSS attack. Note that applications using the normal escaping mechanisms provided by Rails may not impacted, but applications that bypass the escaping mechanisms, or do not use them may be vulnerable.

Metrics

EPSS Probability

1.82%

75.9th percentile

Probability of exploitation in the next 30 days. Learn more

Weakness Enumeration

Affected Software

Vendor	Product	Versions
Rack Project	Rack	>= 1.6.0, < 1.6.11
Rack Project	Rack	>= 2.0.0, < 2.0.6
Debian	Debian Linux	8.0

References

Timeline

Published: Nov 13, 2018
Last Modified: Jun 17, 2026
Status: Modified

Frequently Asked Questions

What is CVE-2018-16471?

There is a possible XSS vulnerability in Rack before 2.0.6 and 1.6.11. Carefully crafted requests can impact the data returned by the `scheme` method on `Rack::Request`. Applications that expect the scheme to be limited to 'http' or 'https' and do not escape the return value could be vulnerable to an XSS attack. Note that applications using the normal escaping mechanisms provided by Rails may not impacted, but applications that bypass the escaping mechanisms, or do not use them may be vulnerable.

How severe is CVE-2018-16471?

Severity scoring for CVE-2018-16471 is pending analysis. The EPSS model estimates a 1.82% probability of exploitation in the next 30 days.

How do I fix CVE-2018-16471?

Check the vendor references and advisories linked above for patched versions and mitigation guidance. You can also run a Strix scan to test if your systems are affected.