CVE-2026-103261

Tornado before 6.5.9 Denial of Service via Query String

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.

Scores

Weaknesses (CWE)

• CWE-770

Advisories

• GHSA-3hv7-mjh2-fv65 — Tornado: Unbounded query-string argument count allows event-loop-stalling DoS

European references

• ENISA EUVD · EUVD-2026-90655
• GCVE · GCVE-0-2026-103261

Affected products

References

• https://github.com/tornadoweb/tornado/security/advisories/GHSA-3hv7-mjh2-fv65
• https://github.com/tornadoweb/tornado/commit/03945136ea9746eccf61caf88edae39642e59c93
• https://www.vulncheck.com/advisories/tornado-before-6.5.9-denial-of-service-via-query-string

Sources