HighFix available
python-tornado — security advisory
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.
- Products
- python-tornado
- Affected versions
- 4.2.1-1ubuntu2, 4.2.1-1ubuntu3, 4.2.1-1ubuntu3.1, 4.2.1-1ubuntu3.1+esm1, 4.2.1-1ubuntu3.1+esm2, 4.2.1-1ubuntu3.1+esm3, 4.5.1-2.1~build2, 4.5.2-1, 4.5.3-1, 4.5.3-1ubuntu0.1, 4.5.3-1ubuntu0.2, 4.5.3-1ubuntu0.2+esm1, 4.5.3-1ubuntu0.2+esm2, 4.5.3-1ubuntu0.2+esm3, 6.1.0-1build1, 6.1.0-2, 6.1.0-3, 6.1.0-3build1, 6.1.0-3ubuntu0.1~esm1, 6.1.0-3ubuntu0.1~esm2, 6.1.0-3ubuntu0.1~esm4, 6.1.0-3ubuntu0.1~esm5, 6.3.2-1, 6.4.0-0ubuntu1, 6.4.0-1, 6.4.0-1build1, 6.4.0-1ubuntu0.1, 6.4.0-1ubuntu0.2, 6.4.0-1ubuntu0.4, 6.4.0-1ubuntu0.5, 6.4.2-3, 6.5.2-3, 6.5.4-0.1, 6.5.4-0.1ubuntu0.1
- Fixed versions
- 4.2.1-1ubuntu3.1+esm4, 4.5.3-1ubuntu0.2+esm4, 6.1.0-3ubuntu0.1~esm6, 6.4.0-1ubuntu0.6, 6.5.4-0.1ubuntu0.2
- CVEs
- CVE-2026-91990
- Confirmed fixed CVEs
- Not specified
- Updated in this feed
- 31 Oct 2026, 20:07 UTC · Revision 1
Source evidence
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.
osv:UBUNTU-CVE-2026-91990
python-tornado
Fixed versions: 4.2.1-1ubuntu3.1+esm4
python-tornado
Fixed versions: 4.5.3-1ubuntu0.2+esm4
python-tornado
Fixed versions: 6.1.0-3ubuntu0.1~esm6
python-tornado
Fixed versions: 6.4.0-1ubuntu0.6
python-tornado
Fixed versions: 6.5.4-0.1ubuntu0.2
Complete source record
{
"id": "16a6a2a8ab66b94da44b647834b5d4dbe50038149fcdf08d883c7e397d0297f1",
"url": "https://osv.dev/vulnerability/UBUNTU-CVE-2026-91990",
"method": "structured",
"payload": {
"kind": "advisory",
"title": "UBUNTU-CVE-2026-91990",
"summary": "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.",
"evidence": "osv:UBUNTU-CVE-2026-91990",
"products": [
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"evidence": "/affected/0/versions"
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{
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{
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"affected_versions": [
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{
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"evidence": "/affected/2/versions"
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{
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{
"value": "6.1.0-3build1",
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{
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{
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{
"name": {
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{
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"affected_versions": [
{
"value": "6.3.2-1",
"evidence": "/affected/3/versions"
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{
"value": "6.4.0-0ubuntu1",
"evidence": "/affected/3/versions"
},
{
"value": "6.4.0-1",
"evidence": "/affected/3/versions"
},
{
"value": "6.4.0-1build1",
"evidence": "/affected/3/versions"
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{
"value": "6.4.0-1ubuntu0.1",
"evidence": "/affected/3/versions"
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{
"value": "6.4.0-1ubuntu0.2",
"evidence": "/affected/3/versions"
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{
"value": "6.4.0-1ubuntu0.4",
"evidence": "/affected/3/versions"
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{
"value": "6.4.0-1ubuntu0.5",
"evidence": "/affected/3/versions"
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},
{
"name": {
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"evidence": "/affected/4/package/name"
},
"prerequisites": [],
"fixed_versions": [
{
"value": "6.5.4-0.1ubuntu0.2",
"evidence": "/affected/4/ranges"
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],
"affected_versions": [
{
"value": "6.4.2-3",
"evidence": "/affected/4/versions"
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{
"value": "6.5.2-3",
"evidence": "/affected/4/versions"
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{
"value": "6.5.4-0.1",
"evidence": "/affected/4/versions"
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{
"value": "6.5.4-0.1ubuntu0.1",
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],
"severity": "high",
"structured": {
"id": "UBUNTU-CVE-2026-91990",
"aliases": [
"UBUNTU-CVE-2026-91990"
],
"metrics": [
{
"type": "CVSS_V3",
"score": "CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:N/I:N/A:H"
},
{
"type": "CVSS_V4",
"score": "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"
},
{
"type": "Ubuntu",
"score": "medium"
}
],
"affected": [
{
"ranges": [
{
"type": "ECOSYSTEM",
"events": [
{
"introduced": "0"
},
{
"fixed": "4.2.1-1ubuntu3.1+esm4"
}
]
}
],
"package": {
"name": "python-tornado",
"purl": "pkg:deb/ubuntu/python-tornado?arch=source&distro=esm-infra-legacy%2Fxenial",
"ecosystem": "Ubuntu:Pro:16.04:LTS"
},
"versions": [
"4.2.1-1ubuntu2",
"4.2.1-1ubuntu3",
"4.2.1-1ubuntu3.1",
"4.2.1-1ubuntu3.1+esm1",
"4.2.1-1ubuntu3.1+esm2",
"4.2.1-1ubuntu3.1+esm3"
],
"database_specific": {
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},
"ecosystem_specific": {
"binaries": [
{
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"binary_version": "4.2.1-1ubuntu3.1+esm4"
},
{
"binary_name": "python3-tornado",
"binary_version": "4.2.1-1ubuntu3.1+esm4"
}
],
"availability": "Available with Ubuntu Pro with Legacy support add-on: https://ubuntu.com/pro"
}
},
{
"ranges": [
{
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"package": {
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},
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"4.5.2-1",
"4.5.3-1",
"4.5.3-1ubuntu0.1",
"4.5.3-1ubuntu0.2",
"4.5.3-1ubuntu0.2+esm1",
"4.5.3-1ubuntu0.2+esm2",
"4.5.3-1ubuntu0.2+esm3"
],
"database_specific": {
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},
"ecosystem_specific": {
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{
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{
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"6.1.0-3ubuntu0.1~esm2",
"6.1.0-3ubuntu0.1~esm4",
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{
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{
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}
}
],
"modified": "2026-10-22T23:20:52.926301544Z",
"provider": "osv",
"upstream": [
"CVE-2026-91990"
],
"references": [
"https://ubuntu.com/security/CVE-2026-91990",
"https://www.cve.org/CVERecord?id=CVE-2026-91990",
"https://github.com/tornadoweb/tornado/security/advisories/GHSA-8423-8fgw-73vq",
"https://ubuntu.com/security/notices/USN-8952-1"
]
},
"related_cves": [
{
"value": "CVE-2026-91990",
"evidence": "/upstream"
}
],
"security_relevant": true,
"severity_evidence": "/severity/1/score"
},
"source_id": "core-osv",
"document_id": 410135,
"published_at": "2026-09-15T16:17:00+00:00"
}