Reject hostnames with unpaired UTF-16 surrogates#9499
Open
eyupcanakman wants to merge 1 commit into
Open
Conversation
isAscii() treated a lone UTF-16 surrogate as ASCII because okio encodes it as one `?` byte. Scan the string so any non-ASCII code unit is detected. Fixes square#6357
JakeWharton
approved these changes
Jun 22, 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
2 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Outdated suggestions cannot be applied.This suggestion has been applied or marked resolved.Suggestions cannot be applied from pending reviews.Suggestions cannot be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.
OkHostnameVerifier.isAscii()usedlength == utf8Size()to decide whether a hostname is ASCII. That breaks on unpaired UTF-16 surrogates. okio encodes a lone surrogate as a single?byte, so its UTF-8 size equals its length andisAscii()wrongly returns true. A hostname that starts with an unpaired surrogate such as U+D800 then slips past the ASCII guard inverify()and can match a wildcard certificate like*.com.The fix scans the string and returns false as soon as a code unit falls outside the ASCII range, so any unpaired surrogate counts as non-ASCII. I added a test that builds a
*.comcertificate and checks a surrogate hostname is rejected while a normal one still matches.Fixes #6357