CVE-2026-91990: tornadoweb tornado
CVSS: 8.7v4.0HighDeferred
AliasesGHSA-8423-8fgw-73vqUBUNTU-CVE-2026-91990DEBIAN-CVE-2026-91990
Published 15-09-2026Last modified 15-09-2026
Vulnerability summary
CVE-2026-91990 is a high (CVSS 8.7) vulnerability in tornadoweb tornado. EPSS estimates a 0.42% chance of exploitation in the next 30 days, higher than 35.2% of scored vulnerabilities.
CVSS score
8.7/10
010
High · v4.0 (CVE.org)EPSS score
0.42%
0%100%
Low · +0.01 pp in 30 daysKEVNot listedIn no KEV catalog
RansomwareNone recordedNo known use recorded
Public exploits0No public exploits recorded
Advisory lineage
Upstream 0 · Downstream 7 · Related 4Timeline
- 15-09-2026PublishedVulnerability first disclosed.
- 15-09-2026Last modifiedVulnerability information updated.
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 metrics
8 scores · 5 sources · 2 versionsHigh 8.7Preferred score · CVE.org (CNA)
CVSS:4.0/AV:N/AC:L/AT:N/PR:N/UI:N/VC:N/VI:N/VA:H/SC:N/SI:N/SA:NSources5 sources · 6.9–8.7
- OSV · PypiEcosystem advisory · calculated6.9MediumCVSS:4.0/AV:N/AC:L/AT:N/PR:N/UI:N/VC:N/VI:N/VA:L/SC:N/SI:N/SA:NDiffers
- OSV · UbuntuEcosystem advisory · calculated8.7HighCVSS:4.0/AV:N/AC:L/AT:N/PR:N/UI:N/VC:N/VI:N/VA:H/SC:N/SI:N/SA:N
- OSV · DebianEcosystem advisory · calculated8.7HighCVSS: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
- NVDNIST8.7HighCVSS: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
High 7.5Preferred score · CVE.org (CNA)
CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:N/I:N/A:HSourcesAll 3 agree
- OSV · UbuntuEcosystem advisory · calculated7.5HighCVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:N/I:N/A:H
- NVDNIST7.5HighCVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:N/I:N/A:H
EPSS trend
Probability
0.42%
Chance of exploitation in the next 30 days
Percentile
35%
Versus all other CVEs
30-day change
+0.01 pp
From 0.41% on 19-09-2026
19-09-202619-10-2026
EPSS score0.42%
Known exploited
Compare KEV catalogsNot in any of the 3 tracked catalogs.
Public exploits
0 foundNo public exploits indexed.
Weaknesses
CWE · root causeAffected systems
Debian1 product
- python-tornadoAll versions (No fix recorded)
PyPI1 product
- tornado< 6.5.8
Tornadoweb1 product
- tornado< 6.5.8
Ubuntu1 product
- python-tornadoAll versions (No fix recorded)
4 vendors · 4 products
