sqlparse: Quadratic O(n²) DoS in group_comments

Exploitation

No confirmed exploitation recorded. Patch Next marks exploitation only from CISA KEV.

CVSS 4.0

8.7 · CVSS:4.0/AV:N/AC:L/AT:N/PR:N/UI:N/VC:N/VI:N/VA:H/SC:N/SI:N/SA:N · score source

EPSS

• CVE-2026-71491: 0.26% estimated exploitation activity in the next 30 days; percentile 18.18 (FIRST EPSS, 2026-11-03). This is a model estimate, not proof of exploitation or customer exposure.

As published by the source; long descriptions are shortened.

Summary A comment-only statement (-- c\nn) may cause a Denial of Service (DoS). Details Location: sqlparse/engine/grouping.py:331-341 (groupcomments), invoked first in group() at grouping.py:439. Reachable via sqlparse.parse() and sqlparse.format(sql, stripcomments=True). A statement made of many single-line comments ('-- c\n' repeated) lexes in O(n) but groupcomments is O(n²): The while loop runs n times and each tokennextby / tokennotmatching rescans the O(n) remaining tokens. When all tokens are comments/newlines nothing ever groups, yet the full scan is repeated per token. Two following factors increase the severity: 1. groupcomments runs first in group() (grouping.py:439), before the groupmatching token-count guard (grouping.py:34-39). So the entire quadratic cost is paid even on oversized input. MAXGROUPINGTOKENS does not provide protection on this vector. 2. It sits on the primary sanitizer path: format(sql, stripcomments=True), used by query loggers, SQL firewalls, ORMs, and…

Published by the source

17 Aug 2026, 17:21 UTC

Last modified by the source

17 Aug 2026, 17:21 UTC

Source last checked

26 Oct 2026, 13:50 UTC

1. Revision 1 · created · 26 Oct 2026

   Published from ghsa record GHSA-f2ff-p2ww-7p4p

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# Patch Next advisory brief: CVE-2026-71491

Advisory: sqlparse: Quadratic O(n²) DoS in group_comments
IDs: CVE-2026-71491, GHSA-f2ff-p2ww-7p4p
Record: https://patchnext.com/advisories/cve-2026-71491 (revision 1, source checked 26 Oct 2026, 13:50 UTC)
Inventory: none attached. This brief comes from a public page and does not say whether any deployment is affected.
Severity: High (CVSS 8.7)
Exploitation: no confirmed exploitation recorded. Patch Next confirms exploitation only from CISA KEV.
Vendor response: Vendor fix available; fixed versions by package: sqlparse 0.6.0. A vendor fix does not mean a deployment is fixed.

## Affected components
- PyPI sqlparse: affected <= 0.5.5; fixed in 0.6.0

## Suggested inspection (read-only)
- `python -m pip show sqlparse`: prints the installed version. Run with the environment that serves production active.

## Supported action
Upgrade each affected component to a fixed version on its release line. For a transitive dependency, upgrade the parent package or add an override or constraint, then regenerate the lockfile. Redeploy every environment that ran an affected version.

## Required regression checks
- Run the test suite and a production build.
- Exercise the features that depend on sqlparse.
- Repeat the inspection and confirm that only fixed versions remain installed.

## Rollback considerations
- Keep the previous lockfile and deployment artifact. Rolling back reinstates the vulnerable version, so apply any documented mitigation while you fix forward.

## Unresolved questions
- Which deployments run an affected version?
- Exploitation status can change. Check again before lowering the priority.
- Mark the work resolved only after the fixed version is verified in production.

## Sources
- Verified: https://github.com/advisories/GHSA-f2ff-p2ww-7p4p (GitHub-reviewed advisory GHSA-f2ff-p2ww-7p4p lists affected ranges: PyPI sqlparse >=0 <=0.5.5)

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