CVE-2026-82397 (GCVE-0-2026-82397)
Vulnerability from cvelistv5 – Published: 2026-08-31 21:28 – Updated: 2026-09-02 17:39
VLAI
EPSS
VEX
Title
Tornado: Urlencoded body parsing omits max_num_fields, so one request can stall the event loop
Summary
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.
Severity
7.5 (High)
SSVC
Exploitation: none
Automatable: yes
Technical Impact: partial
CISA Coordinator · CISA-ADP (v2.0.3)
Decision recorded 2026-09-02 17:39 UTC
CWE
Assigner
References
4 references
| URL | Tags |
|---|---|
| https://github.com/tornadoweb/tornado/security/ad… | x_refsource_CONFIRM |
| https://github.com/tornadoweb/tornado/pull/3704 | x_refsource_MISC |
| https://github.com/tornadoweb/tornado/commit/8d63… | x_refsource_MISC |
| https://github.com/tornadoweb/tornado/releases/ta… | x_refsource_MISC |
Impacted products
1 product
| Vendor | Product | Version | CPE status | |
|---|---|---|---|---|
| tornadoweb | tornado |
Affected:
< 6.5.8
|
guessed |
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Browse all ATT&CK techniques and the vulnerabilities related to each.
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