Tornado before 6.5.8 Cookie Attribute Injection via Capitalized kwargs (CVE-2026-91991) | HOL Guard CVE

Unknown severity · Source severity not reportedCVE-2026-91991

Tornado before 6.5.8 Cookie Attribute Injection via Capitalized kwargs

Answer in brief

CVE-2026-91991 records a Unknown severity vulnerability in Tornado before 6.5.8 Cookie Attribute Injection via Capitalized kwargs. The current sources do not mark it as known exploited. The current feed maps tornadoweb/tornado (generic). Check affected ranges and fixed versions before updating.

Analysis pending evidence review

HOL Guard separates source facts from reviewed analysis. See the methodology.

Published Sep 15, 2026Updated Sep 15, 2026Source checked Sep 15, 2026First seen by HOL Sep 15, 2026Material review Sep 15, 2026

Upstream Advisory

Key facts

Risk: Unknown severitySource severity not reported
Exploitation: Not marked as known exploited
Affected software: 1 mapped package or product
Fix availability: Available

Why this deserves its current priority

A CVSS score is not reported in the current record. The current sources do not mark it as known exploited. Treat this as a source-backed prioritization signal, not a statement about your environment.

Analysis status

Analysis pending evidence review

Factual feed record only; HOL analysis is not approved for indexing. Read the methodology.

Affected scope and exposure questions

The current feed maps tornadoweb/tornado (generic). Check affected ranges and fixed versions before updating.

Mapped affected packages and fixed versions
Package	Affected range	Fixed version
tornadoweb/tornadogeneric	>=6.5.5 <6.5.8	6.5.8

Recommended response

Check inventory. Check lockfiles and deployed manifests for tornadoweb/tornado.
Review the reported fix. Update tornadoweb/tornado to 6.5.8 if you use the affected versions. Test the change in a non-production environment first.

Evidence timeline and material changes

Published upstream
Sep 15, 2026
Evidence: source:cvelist:source_dates:source-dates:record
Source modified
Sep 15, 2026
Evidence: source:cvelist:source_dates:source-dates:record
First seen by HOL
Sep 15, 2026

Sources and claim methodology

Upstream source description

Tornado before 6.5.8 contains an incomplete fix for cookie attribute injection that allows attackers to inject arbitrary cookie attributes by passing capitalized or legacy keyword arguments to set_cookie. Attackers can embed semicolon-delimited data in capitalized parameters like Domain, Path, or SameSite to bypass validation and modify cookie security attributes.

Quoted source text, attributed separately from HOL analysis.