fix(routing): return 404 for dynamic segments with un-decodable percent-encoded sequences#92557
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sleitor wants to merge 1 commit intovercel:canaryfrom
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fix(routing): return 404 for dynamic segments with un-decodable percent-encoded sequences#92557sleitor wants to merge 1 commit intovercel:canaryfrom
sleitor wants to merge 1 commit intovercel:canaryfrom
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…nt-encoded sequences Previously, requests to dynamic routes with malformed percent-encoding (e.g. /foo/%A0 where %A0 is not a valid UTF-8 sequence) produced inconsistent responses: a 400 in development and a 500 in production. Both are incorrect. An un-decodable URL cannot match any real resource, so the correct response is 404 Not Found. Fix: in resolve-routes.ts, catch DecodeError thrown by route.match() in the dynamic route loop (checkTrue) and in the custom-route handler (handleRoute). When the error occurs, skip the route instead of propagating — this lets the request fall through to 404 handling. Fixes vercel#92527
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What?
Dynamic routes like
/foo/[slug]produce inconsistent errors when the URL contains a percent-encoded sequence that is not valid UTF-8 (e.g./foo/%A0):Why?
When
route.match()inresolve-routes.tsis called for a dynamic route against a URL with an un-decodable segment, it callsdecodeURIComponent('%A0')which throws aURIError. This was wrapped into aDecodeErrorinroute-matcher.ts, but in certain production paths the error propagated unhandled, resulting in a 500.More importantly, both 400 and 500 are wrong responses. A URL that cannot be decoded cannot match any real resource — the correct response is 404 Not Found.
How?
Catch
DecodeErrorthrown byroute.match()at both call sites inresolve-routes.ts:checkTrue()— the dynamic route loop used for filesystem-based route resolution. When aDecodeErroris caught,continueto the next route, allowing the request to fall through to 404 handling.handleRoute()— the custom-route handler (headers, redirects, rewrites). When aDecodeErroris caught,return(no match), so the loop continues.A new e2e test (
test/e2e/app-dir/dynamic-segment-invalid-encoding) covers both the broken case (%A0→ 404) and the valid case (%20→ 200).Fixes #92527