[release/10.0] Fix Uri.TryUnescapeDataString throwing instead of returning false with small destination buffers#128610
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…h small destination buffers Co-authored-by: MihaZupan <25307628+MihaZupan@users.noreply.github.com>
Co-authored-by: MihaZupan <25307628+MihaZupan@users.noreply.github.com>
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This was referenced May 27, 2026
rzikm
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May 27, 2026
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Backport of #124655 to release/10.0
Closes #128608
Customer Impact
The new API was added in .NET 9 (#98074) and shipped with a bug where providing a small buffer unexpectedly throws for some inputs. This is a
Try-based API, so callers expect it to returnfalsefor this condition instead of throwing.The issue was originally discovered internally when we added fuzzing for Uri (Feb 2026, #124654).
It was also reported by customers when they started using the new API (May 2026, #128608).
It wasn't reported earlier as it's a new API, and common calling patterns avoid the bug by providing a sufficiently large buffer in the first place. This is common with this particular operation because the output length will always be <= the input length.
Regression
The new API was introduced in .NET 9 and shipped with this bug.
Testing
A targeted test case was added.
Risk
Low.
The change is trivial, covered by a targeted test case, and underwent fuzzing.