CVE-2026-91990

Tornado before 6.5.8 Memory Amplification DoS via multipart

At a glance

Severity: HIGH 8.7
EPSS: EPSS 0.42 % · percentile 36 (2026-10-27)
State: PUBLISHED
Published: 2026-09-15
Updated: 2026-09-15
Assigner: VulnCheck
NVD status: Deferred

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.

Scores

Version	Score	Vector	Scored by
CVSS 4.0	HIGH 8.7	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	VulnCheck
CVSS 3.1	HIGH 7.5	CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:N/I:N/A:H	VulnCheck
CVSS 4.0	HIGH 8.7	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:X/V:X/RE:X/U:X	NVD · disclosure@vulncheck.com (Secondary)
CVSS 3.1	HIGH 7.5	CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:N/I:N/A:H	NVD · disclosure@vulncheck.com (Secondary)

Weaknesses (CWE)

CWE-770

Advisories

GHSA-8423-8fgw-73vq — tornado: multipart split() creates huge temp list before max_parts check -> memory amplification DoS (httputil.py:34)

European references

ENISA EUVD · EUVD-2026-78661
GCVE · GCVE-0-2026-91990

Affected products

Product	Versions
tornadoweb · tornado	affected 0 < 6.5.8 ; unaffected 6.5.8

References

Sources

Source	Licence
CVE List (CVEProject cvelistV5)	CVE Program Terms of Use
EPSS (FIRST.org)	FIRST — attribution requested
ENISA EUVD	ENISA — reproduction authorised, source acknowledged
NVD (NIST) via fkie-cad/nvd-json-data-feeds	Public domain — this product uses data from the NVD API but is not endorsed or certified by the NVD