Reported by GitHub_M · Published April 2, 2026
Rack is a modular Ruby web server interface. Prior to versions 2.2.23, 3.1.21, and 3.2.6, Rack::Sendfile#map_accel_path interpolates the value of the X-Accel-Mapping request header directly into a regular expression when rewriting file paths for X-Accel-Redirect. Because the header value is not escaped, an attacker who can supply X-Accel-Mapping to the backend can inject regex metacharacters and control the generated X-Accel-Redirect response header. In deployments using Rack::Sendfile with x-accel-redirect, this can allow an attacker to cause nginx to serve unintended files from configured internal locations. This issue has been patched in versions 2.2.23, 3.1.21, and 3.2.6.
| Vendor | Product | Versions |
|---|---|---|
| rack | rack | < 2.2.23, >= 3.0.0.beta1, < 3.1.21, >= 3.2.0, < 3.2.6 |
| rack | rack | < 2.2.23, >= 3.0.0.beta1, < 3.1.21, >= 3.2.0, < 3.2.6 |