High severity · published Sep 15, 2026
CVE-2026-91990
Tornado before 6.5.8 Memory Amplification DoS via multipart
7.5
CVSS
0.4%
EPSS
No
On KEV
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 vector
CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:N/I:N/A:H
Attack vector
Network
Complexity
Low
Privileges
None
User interaction
None
Confidentiality
None
Integrity
None
Availability
High
Scope
Unchanged
Exploitation
Is it being used?
Exploit prediction (EPSS)0.4% · higher than 36% of CVEs
Exploited in the wildNo evidence yet
CISA KEVNot listed
Ransomware campaign useNot known
Affected products
Which versions
TO
tornado · tornadoweb
before 6.5.8 · source: vendor
References
NVD
https://nvd.nist.gov/vuln/detail/CVE-2026-91990
CVE.org
https://www.cve.org/CVERecord?id=CVE-2026-91990
github.com
https://github.com/tornadoweb/tornado/security/advisories/GHSA-8423-8fgw-73vq
www.vulncheck.com
https://www.vulncheck.com/advisories/tornado-before-6.5.8-memory-amplification-dos-via-multipart
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