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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.

When SQL is formatted with reindentation enabled, ReindentFilter repeatedly rebuilds prefixes of the current statement to calculate token offsets. An attacker who controls SQL sent to this opt-in formatting path can supply a parenthesized tuple list that remains just below the grouping-token cap. Thousands of offset calculations then traverse an expanding token tree, causing multi-second CPU consumption from an input of roughly 16 KB and degrading service availability.

A comment-only statement (-- c\n*n) may cause a Denial of Service (DoS).

The below gist hangs while attempting to format a long list of tuples.

The documented Python and PHP output modes generate source-code snippets from caller-supplied SQL. Their output filters escape quote characters without first escaping existing backslashes. Crafted SQL can therefore neutralize the generated quote escape, terminate the intended language string, and place attacker-controlled code into the generated snippet. If a downstream consumer executes or imports that generated source, the injected code runs in the consumer's environment.

sqlparse ships hard limits (MAX_GROUPING_DEPTH=100, MAX_GROUPING_TOKENS=10000) intended to bound parsing work on attacker-supplied SQL, but the path that reaches those limits is itself O(n*depth) per token-group construction. A ~1-2 KB SQL payload (e.g. SELECT (((((1))))) ... with 500-2000 nesting levels, or a 200-400-level nested CASE WHEN chain) drives the parser to spend multiple seconds of CPU before the depth cap raises SQLParseError. Concretely: a 2 KB malicious payload consumes ~10 seconds of CPU per request on a single worker (~5000x CPU-to-input amplification), while a benign 1 KB SQL completes in ~3 ms.