Handle %2f in routing more consistently - #19537
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Currently path prefix matching does not treat %2f as /, and `Route` has an option for it. In the past we've made changes in this area (#18050, #16110) to make urldecoding optional, and to intentionally decode urlencoding in path segments to support non-ascii applications. We got a report on the security list for a potential issue where *if* an application enforced authorization within path prefixed scopes, and had fallback routes enabled, then one could potentially bypass the scoped middleware and hit the fallback routes which inconsistently handle %2f. These changes align the behavior of urldecoding between RouteCollection and Route with a new shared internal function. I thought a function was better than exposing a static method on a public class. Thanks to Rotem Reiss for reporting this issue.
Been writing too much python and rust lately.
markstory
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Currently path prefix matching does not treat %2f as /, and `Route` has an option for it. In the past we've made changes in this area (#18050, #16110) to make urldecoding optional, and to intentionally decode urlencoding in path segments to support non-ascii applications. We got a report on the security list for a potential issue where *if* an application enforced authorization within path prefixed scopes, and had fallback routes enabled, then one could potentially bypass the scoped middleware and hit the fallback routes which inconsistently handle %2f. These changes align the behavior of urldecoding between RouteCollection and Route with a new shared internal function. I thought a function was better than exposing a static method on a public class. Thanks to Rotem Reiss for reporting this issue.
markstory
added a commit
that referenced
this pull request
Jul 14, 2026
Currently path prefix matching does not treat %2f as /, and `Route` has an option for it. In the past we've made changes in this area (#18050, #16110) to make urldecoding optional, and to intentionally decode urlencoding in path segments to support non-ascii applications. We got a report on the security list for a potential issue where *if* an application enforced authorization within path prefixed scopes, and had fallback routes enabled, then one could potentially bypass the scoped middleware and hit the fallback routes which inconsistently handle %2f. These changes align the behavior of urldecoding between RouteCollection and Route with a new shared internal function. I thought a function was better than exposing a static method on a public class. Thanks to Rotem Reiss for reporting this issue.
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Currently path prefix matching does not treat %2f as /, and
Routehas an option for it. In the past we've made changes in this area (#18050, #16110) to make urldecoding optional, and to intentionally decode urlencoding in path segments to support non-ascii applications.We got a report on the security list for a potential issue where if an application enforced authorization within path prefixed scopes, and had fallback routes enabled, then one could potentially bypass the scoped middleware and hit the fallback routes which inconsistently handle %2f.
These changes align the behavior of urldecoding between RouteCollection and Route with a new shared internal function. I thought a function was better than exposing a static method on a public class.
Thanks to Rotem Reiss for reporting this issue.