Login Request a demo
Medium severity · published Oct 1, 2026
CVE-2026-103261
Tornado before 6.5.9 Denial of Service via Query String
5.3
CVSS
0.5%
EPSS
No
On KEV
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.
CVSS vector
CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:N/I:N/A:L
Attack vector
Network
Complexity
Low
Privileges
None
User interaction
None
Confidentiality
None
Integrity
None
Availability
Low
Scope
Unchanged
Exploitation
Is it being used?
Exploit prediction (EPSS)0.5% · higher than 40% of CVEs
Exploited in the wildNo evidence yet
CISA KEVNot listed
Ransomware campaign useNot known
Affected products
Which versions
TO
tornado · tornadoweb
before 6.5.9 · source: vendor
Affected product
TO
tornado
tornadoweb
References
NVD
https://nvd.nist.gov/vuln/detail/CVE-2026-103261
CVE.org
https://www.cve.org/CVERecord?id=CVE-2026-103261
vendor-advisory
https://github.com/tornadoweb/tornado/security/advisories/GHSA-3hv7-mjh2-fv65
patch
https://github.com/tornadoweb/tornado/commit/03945136ea9746eccf61caf88edae39642e59c93
third-party-advisory
https://www.vulncheck.com/advisories/tornado-before-6.5.9-denial-of-service-via-query-string
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