Resource exhaustion in Tornadoweb Tornado
CVE-2026-31958
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.
Vulnerability class: DoS (Denial of Service)
Published · last modified .
CVSS v3 metric
CVSS v3 base score 7.5 (High). Vector: CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:N/I:N/A:H.
EPSS exploit prediction
EPSS: 0.004 (30.6th percentile), scored .
Very low probability of exploitation in the next 30 days; routine patching cadence is appropriate. 31st percentile — 30.6% of CVEs in the catalogue have a lower EPSS than this one. How to read EPSS.
EPSS over last 30 days · oldest: 0.004 · newest: 0.004 · change: +0.000
Affected products
- Tornadoweb Tornado — versions < 6.5.5
Weakness classification (CWE)
References
Frequently asked questions
- What is CVE-2026-31958?
- CVE-2026-31958 is a high-severity vulnerability in Tornadoweb Tornado, classified under Uncontrolled Resource Consumption. CVSS score: 7.5/10. Published 2026-03-11.
- How severe is CVE-2026-31958?
- High severity. CVSS v3 base score is 7.5 out of 10.