Allocation of Resources Without Limits or Throttling Affecting tornado package, versions [,6.5.9)
Threat Intelligence
Snyk has a proof-of-concept or detailed explanation of how to exploit this vulnerability.
The probability is the direct output of the EPSS model, and conveys an overall sense of the threat of exploitation in the wild. The percentile measures the EPSS probability relative to all known EPSS scores. Note: This data is updated daily, relying on the latest available EPSS model version. Check out the EPSS documentation for more details.
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Start learning- Snyk IDSNYK-PYTHON-TORNADO-20415625
- published3 Oct 2026
- disclosed1 Oct 2026
- creditUnknown
Introduced: 1 Oct 2026
NewCVE-2026-103261 (opens in a new tab)How to fix?
Upgrade tornado to version 6.5.9 or higher.
Overview
tornado is a Python web framework and asynchronous networking library, originally developed at FriendFeed.
Affected versions of this package are vulnerable to Allocation of Resources Without Limits or Throttling in HTTPServerRequest.__init__ in tornado/httputil.py via query strings with a large number of fields. The parse_qs_bytes call used to parse the query string had no argument count limit, allowing an attacker to send a request with a query string containing a very large number of fields and trigger superlinear CPU consumption. In the default configuration, max_header_size (64 KB) caps the query string at roughly 12,700 arguments, which still imposes approximately 47 ms of CPU per request - an order of magnitude beyond the limit enforced on the body path - and applications that raise max_header_size face a proportionally larger impact.