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Vulnerability record · CVE-2026-91990 · published 15 September 2026

CVE-2026-91990: Allocation without limits vulnerability

Tornado before 6.5.8 contains a memory amplification vulnerability in parse_multipart_form_data that splits multipart data before validating the max_parts limit. Attackers can send crafted multipart requests with many parts to create large transient lists, exhausting server memory and causing denial of service.

8.7 CVSS 4.0 High EPSS 0.49% · top 60.5% CWE-770 · Allocation without limits Deferred
8.7CVSS 4.0 base score
0.49%EPSS exploitation probability, 30 days
NoNot in CISA KEV
0Affected product versions listed by NVD
3References
16 Sep 2026Last modified by NVD

Description

Tornado before 6.5.8 contains a memory amplification vulnerability in parse_multipart_form_data that splits multipart data before validating the max_parts limit. Attackers can send crafted multipart requests with many parts to create large transient lists, exhausting server memory and causing denial of service.

CVSS:4.0/AV:N/AC:L/AT:N/PR:N/UI:N/VC:N/VI:N/VA:H/SC:N/SI:N/SA:N/E:X/CR:X/IR:X/AR:X/MAV:X/MAC:X/MAT:X/MPR:X/MUI:X/MVC:X/MVI:X/MVA:X/MSC:X/MSI:X/MSA:X/S:X/AU:X/R:

References

LinkTags
https://github.com/tornadoweb/tornado/security/advisories/GHSA-8423-8fgw-73vq
https://www.vulncheck.com/advisories/tornado-before-6.5.8-memory-amplification-dos-via-multipart
https://github.com/tornadoweb/tornado/security/advisories/GHSA-8423-8fgw-73vq

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Same products first, then exploited flaws of the same weakness class.

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Source: NIST National Vulnerability Database (record CVE-2026-91990), CISA KEV, FIRST EPSS (scores of 2026-09-26). This page is refreshed as NVD updates the record.