Machine-written summary
Summary written by Claude Haiku from the source advisory. Not reviewed by a person.
Tornado versions before 6.5.8 are vulnerable to a memory amplification denial of service in multipart form parsing. The parser splits the request body into a list before checking the max_parts limit, so a crafted body with many parts forces a large temporary allocation. A remote attacker can send such a request without authentication to exhaust server memory. Upgrade to Tornado 6.5.8 or later, which fixes the issue. The source gives few details on the exact mechanics beyond this.
Not analysed yet
We haven’t published our analysis of this Advisory yet. Once a person has reviewed it, this page will say what’s vulnerable, what has to be true for your app to be affected, and how to check.
Severity and exploitation
| Score | Rating | CVSS | Vector | Source |
|---|---|---|---|---|
| 8.7 | High | 4.0 | CVSS:4.0/AV:N/AC:L/AT:N/PR:N/UI:N/VC:N/VI:N/VA:H/SC:N/SI:N/SA:N | CNA (VulnCheck) |
- CISA KEV Not listed.
- EPSS 0.0039, the 33rd percentile, on 14 Nov 2026: FIRST’s estimate of the chance of exploitation in the next 30 days.
Timeline
- 31 Oct 2026, 14:10 UTC First seen by agentprime
- 31 Oct 2026, 14:10 UTC Confirmed by OSV
Sources
- GitHub Advisory Database: GHSA-8423-8fgw-73vq
- OSV: GHSA-8423-8fgw-73vq
- github.com/tornadoweb/tornado/security/advisories/GHSA-8423-8fgw-73vq
- github.com/tornadoweb/tornado/pull/3704
- github.com/tornadoweb/tornado/commit/de85b3f87446e323e881bbaa3d5a74f4b76e5f05
- gist.github.com/afldl/649861f25d39b53b7edbe0298e171617
- github.com/tornadoweb/tornado
- github.com/tornadoweb/tornado/releases/tag/v6.5.8