MEDIUM

CVE-2026-103261

Tornado before 6.5.9 Denial of Service via Query String

CVSS v3

5.3

MEDIUM

EPSS Score

0.5 %

exploit probability, as of 2026-10-19

CISA KEV

known exploited

Exploitation

none

SSVC status

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Affected and fixed versions

Packages from OSV.dev and products from the vendors' CSAF advisories.

version not verifiedVersions not verified: read as OSV.dev and the vendors publish them, not checked against each vendor's release list.

Packages

tornadoPyPIall versions · fixed in 6.5.9

Vendor advisories

CVE-2026-103261 Red Hat Product Security71 known affected
tornado: tornado: Denial of Service (DoS) via unbounded query string parsing
lightspeed-core/lightspeed-stack-rhel9 as a component of Lightspeed Core · lightspeed-core/rag-tool-cpu-rhel9 as a component of Lightspeed Core · lightspeed-core/rag-tool-cuda-12.9-rhel9 as a component of Lightspeed Core

Full record on NVD

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.

Technical details

CVSS v3 Vector: CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:N/I:N/A:L
Published: 2026-10-01
Last Modified: 2026-10-01

Frequently asked questions

What is CVE-2026-103261?

Is CVE-2026-103261 actively exploited?

Active exploitation of CVE-2026-103261 has not been confirmed. Its EPSS score was 0.5% on 2026-10-19, the estimated probability of exploitation in the next 30 days.

What is the CVSS score for CVE-2026-103261?

CVE-2026-103261 has a CVSS v3 base score of 5.3 (MEDIUM severity), with vector string CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:N/I:N/A:L.

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