Fix JIT stack exhaustion in Twig3 compatibility regex patterns #4027
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The regex patterns in rewriteSameAsTests(), rewriteDivisibleByTests(), and rewriteNoneTests() used negative lookahead `(?!\1)` which caused catastrophic backtracking and JIT stack exhaustion when processing content with many Unicode characters (e.g., middle-dots). This fix uses possessive quantifiers (*+) to prevent backtracking: - Handles single and double quotes separately (no backreference needed) - Uses *+ possessive quantifiers to prevent backtracking - Falls back to original content if regex fails Fixes #4015 Co-Authored-By: Claude Opus 4.5 <noreply@anthropic.com>
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Pull request overview
This PR fixes critical JIT stack exhaustion errors in Twig3 regex patterns that occurred when processing content with many Unicode characters (e.g., middle-dots). The issue manifested as blank pages when Twig processing was enabled.
Changes:
- Replaced catastrophic backtracking regex patterns with possessive quantifiers (
*+) - Inverted group capture logic to match the new pattern structure
- Added fallback to return original content if regex fails
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system/src/Grav/Common/Twig/Compatibility/Twig3CompatibilityTransformer.php
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system/src/Grav/Common/Twig/Compatibility/Twig3CompatibilityTransformer.php
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…ansformer.php Co-authored-by: Copilot <175728472+Copilot@users.noreply.github.com>
…ansformer.php Co-authored-by: Copilot <175728472+Copilot@users.noreply.github.com>
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Summary
Fixes the regex patterns in
Twig3CompatibilityTransformerthat caused JIT stack exhaustion when processing content with many Unicode characters (e.g., middle-dots ·).([\'"])(?:\\\\.|(?!\\1).)*\\1used a negative lookahead which caused catastrophic backtracking*+) which prevent backtracking entirelyMethods fixed:
rewriteSameAsTests()rewriteDivisibleByTests()rewriteNoneTests()Test plan
@NoNoNo - Could you please test this fix with your original test case from #4015?
Or manually apply the changes from this PR to your existing installation.
Fixes #4015
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