Tornado before 6.5.9 Denial of Service via Query String (CVE-2026-103261) | HOL Guard CVE

Medium · CVSS 6.9CVE-2026-103261

Tornado before 6.5.9 Denial of Service via Query String

Answer in brief

CVE-2026-103261 records a Medium severity (CVSS 6.9) vulnerability in Tornado before 6.5.9 Denial of Service via Query String. 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 Oct 1, 2026Updated Oct 1, 2026Source checked Oct 1, 2026First seen by HOL Oct 1, 2026Material review Oct 1, 2026

Upstream Advisory

Key facts

Risk: Medium · CVSS 6.9
Exploitation: Not marked as known exploited
Affected software: 1 mapped package or product
Fix availability: Available

Why this deserves its current priority

CVSS is 6.9. 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	>=0 <6.5.9	6.5.9

Recommended response

Check inventory. Check lockfiles and deployed manifests for tornadoweb/tornado.
Review the reported fix. Update tornadoweb/tornado to 6.5.9 if you use the affected versions. Test the change in a non-production environment first.

Evidence timeline and material changes

Published upstream
Oct 1, 2026
Evidence: source:cvelist:source_dates:source-dates:record
Source modified
Oct 1, 2026
Evidence: source:cvelist:source_dates:source-dates:record
First seen by HOL
Oct 1, 2026

Sources and claim methodology

Upstream source description

Tornado before 6.5.9 fails to limit the number of query string fields in HTTPServerRequest.__init__, allowing remote attackers to cause event-loop stalling by sending requests with thousands of query parameters. Attackers can send unauthenticated GET requests with unbounded query-string field counts to degrade response times for all clients sharing the same IOLoop.

Quoted source text, attributed separately from HOL analysis.