CVE-2026-31958
High
Description
Tornado is a Python web framework and asynchronous networking library. In versions of Tornado prior to 6.5.5, the only limit on the number of parts in multipart/form-data is the max_body_size setting (default 100MB). Since parsing occurs synchronously on the main thread, this creates the possibility of denial-of-service due to the cost of parsing very large multipart bodies with many parts. This vulnerability is fixed in 6.5.5.
SeverityHigh
CVSS7.5
Exploit probability—
ProductTornado
PublishedMar 11, 2026
First seenMar 11, 2026
Weakness typeCWE-400Uncontrolled resource consumption
How to fix
Update
- tornadoweb tornado6.5.5 or later
- tornado6.5.5 or later
Affected products
| Product | Affected versions | Fixed in |
|---|---|---|
| tornadoweb tornado | v < 6.5.5 | 6.5.5 |
| tornadoPyPI | v < 6.5.5 | 6.5.5 |
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