fix: preserve percent-encoding in prefix stripping#255
Merged
mcollina merged 1 commit intofastify:mainfrom Mar 5, 2026
Merged
Conversation
When a middleware is registered with a path prefix (e.g. app.use('/prefix', fn)),
the prefix is stripped from req.url before invoking the middleware. The previous
implementation used normalizePathForMatching() which calls sanitizeUrlPath(),
decoding percent-encoded characters (%20, %2F, etc.) before building the new
req.url. This caused encoded characters to appear decoded in req.url.
Fix by trying the regexp against the original sanitized URL first (preserving
percent-encoding). When that matches, slice the original URL and apply only
structural normalizations (duplicate slashes, trailing slash). Fall back to
the fully normalized URL only when normalization was necessary for matching
(e.g. duplicate leading slashes, semicolon delimiters).
gurgunday
approved these changes
Mar 5, 2026
This file contains hidden or bidirectional Unicode text that may be interpreted or compiled differently than what appears below. To review, open the file in an editor that reveals hidden Unicode characters.
Learn more about bidirectional Unicode characters
Sign up for free
to join this conversation on GitHub.
Already have an account?
Sign in to comment
3 participants
Add this suggestion to a batch that can be applied as a single commit.This suggestion is invalid because no changes were made to the code.Suggestions cannot be applied while the pull request is closed.Suggestions cannot be applied while viewing a subset of changes.Only one suggestion per line can be applied in a batch.Add this suggestion to a batch that can be applied as a single commit.Applying suggestions on deleted lines is not supported.You must change the existing code in this line in order to create a valid suggestion.Outdated suggestions cannot be applied.This suggestion has been applied or marked resolved.Suggestions cannot be applied from pending reviews.Suggestions cannot be applied on multi-line comments.Suggestions cannot be applied while the pull request is queued to merge.Suggestion cannot be applied right now. Please check back later.
When a middleware is registered with a path prefix (e.g.
app.use('/prefix', fn)), the prefix is stripped fromreq.urlbefore invoking the middleware. The previous implementation usednormalizePathForMatching()which callssanitizeUrlPath(), decoding percent-encoded characters (%20,%2F, etc.) before building the newreq.url. This caused encoded characters to appear decoded inreq.url.Fix
Try the regexp against the original sanitized URL first (preserving percent-encoding). When that matches, slice the original URL and apply only structural normalizations (duplicate slashes, trailing slash). Fall back to the fully normalized URL only when normalization was necessary for matching (e.g. duplicate leading slashes, semicolon delimiters)
Checklist
npm run test && npm run benchmark --if-presentand the Code of conduct