Machine-written summary
Summary written by Claude Haiku from the source advisory. Not reviewed by a person.
Tornado versions before 6.5.6 are vulnerable. Its optional native extension tornado.speedups does not check that the mask argument to websocket_mask is exactly four bytes, so it can read up to 3 bytes past the end of a short buffer, exposing uninitialized memory. The source says this is reachable through the XSRF token decoder when xsrf_cookies is enabled and the native extension is active. Upgrade to Tornado 6.5.6. Before upgrading, setting the environment variable TORNADO_EXTENSION=0 disables the vulnerable code, at a cost to websocket performance.
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 |
|---|---|---|---|---|
| 5.3 | Medium | 3.1 | CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:L/I:N/A:N | CNA (GitHub_M) |
- CISA KEV Not listed.
- EPSS 0.0042, the 36th percentile, on 6 Nov 2026: FIRST’s estimate of the chance of exploitation in the next 30 days.
Timeline
- 31 Oct 2026, 14:29 UTC First seen by agentprime
- 31 Oct 2026, 14:29 UTC Confirmed by OSV