GHSA-cfqr-cjx5-5jcm sqlparse: Reindentation of tuple lists causes near-cap quadratic CPU consumption

• PyPI sqlparse: < 0.6.0 → fixed in 0.6.0

Summary 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. Details `ReindentFilter._get_offset()` joins the tokens returned by `_flatten_up_to_token()` to calculate the current output position. Each call begins by flattening the current statement from its start and walks until the target token. Tuple-list reindentation invokes this calculation repeatedly as it processes many parenthesized values, so later calls redo an increasingly large amount of prior work. The vulnerable path is reached through `sqlparse.format(sql, reindent=True)` and `sqlformat --reindent`. A carefully sized tuple list completes grouping below the configured token cap and then enters the expensive reindentation path; a slightly larger input may instead be rejected quickly by the cap. Relevant code locations: • `sqlparse/formatter.py:170` — enabling `ReindentFilter` • `sqlparse/filters/reindent.py:30` — repeated flattening from the statement start • `sqlparse/filters/reindent.py:44` — prefix joining for offset calculation • `sqlparse/filters/reindent.py:216` — tuple-list processing path PoC A complete validated reproduction is attached as reindent_tuple_list_cpu_dos-poc.zip. The archive contains `reproduction/` at its root, uses Git and Docker, and compares two same-shape tuple-list inputs formatted with reindentation enabled. Extract the archive beside this report, then run: ```console ./reproduction/run.sh ``` Observed result: The 600-tuple baseline completed in 0.649 seconds, while the below-cap 1,425-tuple input completed in 4.999 seconds. The run emitted `EVOHUNT_REINDENT_DOS_VERIFIED` and completed successfully. Verification method: The verification helper formats two same-shape tuple-list payloads with `reindent=True` and fails unless the larger payload completes successfully, takes at least 2.0 seconds, and takes at least 4x the baseline. Limitations: No reproduction blocker was recorded. Timing varies by host, and exploitation requires the reindentation option or corresponding CLI mode to be enabled. Impact This is a CPU resource-exhaustion vulnerability in workflows that reindent attacker-controlled SQL. A small crafted tuple-list input can occupy a worker for several seconds, enabling request delays, reduced throughput, or worker starvation when payloads are processed repeatedly or concurrently. The affected reindentation behavior is opt-in, and sqlparse itself does not provide network exposure; reachability depends on the consuming application or CLI workflow. The demonstrated effect is CPU consumption in a single formatting call, not process termination, code execution, or confidentiality or integrity impact.