Machine-written summary
Summary written by Claude Haiku from the source advisory. Not reviewed by a person.
Tornado versions before 6.5.9 are affected when the CurlAsyncHTTPClient is used: it places no limit on response body size, so a malicious server sending a gzip decompression bomb can make the client accumulate memory until the process runs out of memory. An attacker only needs to get the application to fetch a URL they control, with no privileges or user interaction required. Upgrade to Tornado 6.5.9, which fixes the issue. The source gives no workaround other than upgrading.
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 0.0063, the 50th percentile, on 5 Nov 2026: FIRST’s estimate of the chance of exploitation in the next 30 days.
Timeline
- 31 Oct 2026, 14:09 UTC First seen by agentprime
- 31 Oct 2026, 14:09 UTC Confirmed by OSV
Sources
- GitHub Advisory Database: GHSA-chx6-46f5-w4vp
- OSV: GHSA-chx6-46f5-w4vp
- github.com/tornadoweb/tornado/security/advisories/GHSA-chx6-46f5-w4vp
- github.com/tornadoweb/tornado/pull/3719
- github.com/tornadoweb/tornado/commit/15f056080d8e456f92cca8ad0c33e5a5480414ac
- github.com/tornadoweb/tornado/commit/6564e0a0922c16f239d3a18adccd04736e380c89
- github.com/tornadoweb/tornado/commit/aa2eb0d989716ac00fe8d7a9919b81c1eccd6ec4
- github.com/tornadoweb/tornado/commit/e412435febba4569c552c5c9054f1bf92bd171a9
- github.com/tornadoweb/tornado
- github.com/tornadoweb/tornado/releases/tag/v6.5.9