Medium 5.3Published Oct 1, 2026

CVE-2026-103261Tornado before 6.5.9 Denial of Service via Query String

Updated under an hour ago (2026-10-19 11:10 UTC)

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It affects tornadoweb tornado. Add what you run to find out whether that includes you.

No exploitation reported and no EPSS estimate yet.

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Every CVE for tornadoweb tornado

Exploited in the last 30 days

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.

CVSS: 5.3 MEDIUM (v3.1, CNA)CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:N/I:N/A:L
Weakness (CWE): CWE-770
Known exploited: Not in CISA's KEV catalog
EPSS (exploitation in the next 30 days): Not loaded for this CVE
Assigned by: VulnCheck
NVD analysis: Deferred
Record last updated: Oct 1, 2026
First seen by InfoSec Signals: Oct 9, 2026

Affected products

Affected products

tornadoweb tornado tornadoweb:tornado (from the name)	before 6.5.9; 6.5.9 not affected	CNA record

References

https://github.com/tornadoweb/tornado/security/advisories/GHSA-3hv7-mjh2-fv65vendor-advisory
https://github.com/tornadoweb/tornado/commit/03945136ea9746eccf61caf88edae39642e59c93patch
https://www.vulncheck.com/advisories/tornado-before-6.5.9-denial-of-service-via-query-stringthird-party-advisory

The CVE record on cve.org NVD's entry

The CVE record is authoritative. Products marked “from the name” were identified from the CNA's free-text names, not a CPE, and are matched less certainly. This product uses the NVD API but is not endorsed or certified by the NVD.