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CVE-2026-82397

Tornado: Urlencoded body parsing omits max_num_fields, so one request can stall the event loop PUBLISHED

Description (CNA)

Tornado is a Python web framework and asynchronous networking library. Prior to 6.5.8, Tornado parses application/x-www-form-urlencoded request bodies with urllib.parse.parse_qs in tornado/escape.py without passing max_num_fields. RequestHandler._execute in tornado/web.py parses the body before handler dispatch through HTTPServerRequest._parse_body and parse_body_arguments in tornado/httputil.py, so an unauthenticated request body containing millions of separator-delimited fields can synchronously stall the single-threaded event loop and delay every connection. The body is bounded only by max_buffer_size, which defaults to 104857600 bytes. This issue is fixed in version 6.5.8.

Affected (CNA)

Vendor / productVersions
tornadoweb / tornadoaffected < 6.5.8

CWE

CWE-400, CWE-1284

References

ADP enrichment

CISA-ADP

No English description supplied.

No references supplied.