What is CVE-2026-103261?

CVE-2026-103261 is a medium-severity vulnerability in Tornadoweb Tornado, classified under Allocation of Resources Without Limits or Throttling. CVSS score: 5.3/10. Published 2026-10-01.

How severe is CVE-2026-103261?

Medium severity. CVSS v3 base score is 5.3 out of 10.

Resource exhaustion in Tornadoweb Tornado

CVE-2026-103261

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.

Published 2026-10-01 · last modified 2026-10-01.

CVSS v3 metric

CVSS v3 base score 5.3 (Medium). Vector: CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:N/I:N/A:L.

EPSS exploit prediction

No EPSS score from FIRST.org yet. New CVEs usually get one within a few days; no score means no signal yet, not low risk. How EPSS works.

Affected products

Tornadoweb Tornado

Weakness classification (CWE)

CWE-770 — Allocation of Resources Without Limits or Throttling

References

github.com/tornadoweb/tornado/security/advisories/GHSA-3hv7-mjh2-fv65 (vendor-advisory)
github.com/tornadoweb/tornado/commit/03945136ea9746eccf61caf88edae39642e59c93 (patch)
www.vulncheck.com/advisories/tornado-before-6.5.9-denial-of-service-via-query-s… (third-party-advisory)

Frequently asked questions

What is CVE-2026-103261?: CVE-2026-103261 is a medium-severity vulnerability in Tornadoweb Tornado, classified under Allocation of Resources Without Limits or Throttling. CVSS score: 5.3/10. Published 2026-10-01.
How severe is CVE-2026-103261?: Medium severity. CVSS v3 base score is 5.3 out of 10.