# Risky Regex Patterns Collection of regex patterns that demonstrate security vulnerabilities, performance issues, and common anti-patterns to avoid > Canonical page: https://elysiatools.com/en/samples/risky-regex - **Category:** Validation - **Keywords:** regex, security, performance, redo, catastrophic backtracking, vulnerability, pattern, validation ## Overview Collection of regex patterns that demonstrate security vulnerabilities, performance issues, and common anti-patterns to avoid ## Examples - **Catastrophic Backtracking Patterns**: Regex patterns that can cause exponential backtracking leading to Denial of Service (ReDoS) - **Unanchored Validation Patterns**: Regex patterns without anchors that can match unintended positions in the input - **Excessive Greedy Matching**: Greedy quantifiers that consume more than intended, causing incorrect matches - **Inefficient Lazy Quantifiers**: Lazy quantifiers that are still inefficient or incorrect for the use case - **Invalid Character Class Escapes**: Character classes with invalid ranges or unescaped special characters - **Ambiguous Alternation Order**: Alternation patterns where order causes unexpected matches - **Confusing Double Negation**: Patterns with double negation that are hard to read and error-prone - **Redundant Escapes**: Unnecessary escape sequences that reduce readability - **Octal and Backreference Ambiguity**: Patterns where \1 could mean octal or backreference - **Excessive Capturing Groups**: Unnecessary capturing groups that impact performance ## When to use - Use this sample set when you want reference inputs for Risky Regex Patterns. - Use it to preview output formats and compare related sample variants. ## How it works - Open a sample entry to inspect the prepared example payload or asset. - Compare it with related tools to understand how the workflow connects. ## Use cases - Catastrophic Backtracking Patterns - Unanchored Validation Patterns - Excessive Greedy Matching - Inefficient Lazy Quantifiers - Invalid Character Class Escapes - Ambiguous Alternation Order ## Frequently asked questions ### What is included in Risky Regex Patterns? This page includes curated sample entries, related tools, and neighboring sample collections for Risky Regex Patterns. ## Related tools - [AI Regex Explainer](https://elysiatools.com/en/tools/ai-regex-explainer): Use AI to break down regular expressions into readable explanations - [Glob to Regex](https://elysiatools.com/en/tools/glob-to-regex): Convert file matching patterns (Glob) to regular expressions - [Regex Debugger](https://elysiatools.com/en/tools/regex-debugger): Step through how a regular expression matches a string position by position: visualize match attempts, partial successes, backtracks, and captures — a learning tool for understanding regex behavior, not just the final result - [Regex Linter](https://elysiatools.com/en/tools/regex-linter): Detect error-prone and risky regex patterns, check for catastrophic backtracking, unanchored patterns, and provide rewrite suggestions - [Regex Replace Previewer](https://elysiatools.com/en/tools/regex-replace-previewer): Preview regex replacements in real-time with detailed diff highlights and statistics - [BGP Community Regex Tester and Looking-Glass Explainer](https://elysiatools.com/en/tools/bgp-community-string-regex-tester-and-looking-glass): Validate RFC 8294 BGP community regex patterns against a set of communities, match sample AS-paths, and generate Cisco/Juniper/FRR route-policy output. - [Regex Railroad Diagram Visualizer](https://elysiatools.com/en/tools/regex-railroad-diagram-visualizer): Render a regular expression as an SVG railroad (syntax) diagram showing literals, groups, alternations, and repetition, with capture-group numbering and flag explanations - [Regex Tester](https://elysiatools.com/en/tools/regex-tester): Test regular expressions against text ## Related content - [Regex Pattern Alternatives](https://elysiatools.com/en/samples/regex-alternatives): Multiple ways to write the same regex pattern with different trade-offs in readability, performance, and accuracy - [Common Regex Patterns](https://elysiatools.com/en/samples/regex-samples): Commonly used regular expression patterns for validation and matching - [Regex Named Capture Groups](https://elysiatools.com/en/samples/regex-named-groups): Collection of regex patterns using named capture groups for extracting structured data from text. Named groups make patterns more readable and maintainable by assigning meaningful names to captured portions. - [Regex Replace Samples](https://elysiatools.com/en/samples/regex-replace): Collection of common and useful regex replacement patterns for text transformation and data cleaning - [Android String Processing Java Samples](https://elysiatools.com/en/samples/android-string-processing-java): Android Java string processing examples including string split and join, regular expressions, and string replacement - [Android String Processing Kotlin Samples](https://elysiatools.com/en/samples/android-string-processing-kotlin): Android Kotlin string processing examples including string split and join, regular expressions, and string replacement