CVE-2026-59893

### Summary sqlparse contains a Regular Expression Denial of Service (ReDoS) vulnerability in its dollar-quoted SQL literal lexer. The regex pattern at `sqlparse/keywords.py:33` uses a backreference (`\1`) to match closing dollar-quote delimiters, causing O(n²) CPU complexity when processing inputs containing many unique, unmatched dollar-quote opening sequences. An attacker who can supply arbitrary SQL text to any application using sqlparse can trigger sustained CPU exhaustion, resulting in a denial of service. No authentication or special privileges are required. **Scope note:** the same regex shape — a lazy dot-all quantifier terminated by a delimiter, applied at every input position by the lexer loop — is also present in the two multiline-comment patterns. Those are covered by this advisory and by the same fix; see "Additional affected pattern: multiline comments" below. ### Details The vulnerable regex is defined in `sqlparse/keywords.py` as part of `SQL_REGEX`: ```python # sqlparse/keywords.py:33 (r'((?<![\w\"\$])\$(?:[_A-ZÀ-Ü]\w*)?\$)[\s\S]*?\1', tokens.Literal), ``` This pattern first captures a dollar-quote delimiter (e.g., `$tag$`) into group 1, then attempts to match any characters (`[\s\S]*?`) up to the same delimiter again via backreference `\1`. When no matching closing delimiter exists, the regex engine exhausts the remaining input before concluding there is no match. For a sequence of N unique unmatched openers, each opener triggers a full scan of the remaining string, yielding O(N²) total regex work. The lexer applies this regex at every character position (`sqlparse/lexer.py:136-138`): ```python # sqlparse/lexer.py:136-138 for pos, char in iterable: for rexmatch, action in self._SQL_REGEX: m = rexmatch(text, pos) ``` The data flow from public API to the vulnerable sink is: 1. `sqlparse/__init__.py:20` — `parse(sql)` accepts caller-controlled SQL. 2. `sqlparse/__init__.py:29` — delegates to `parsestream(sql, encoding)`. 3. `sql