CVE-2026-49853 Tornado: Authorization header forwarded across cross-origin redirects in SimpleAsyncHTTPClient
Attackers can steal sensitive authorization credentials when the Tornado HTTP client follows cross-origin redirects.
- Exploited in the wild
- Not known
- Login needed
- Any signed-in user
- Attackable
- Over the internet
- Victim action needed
- Not needed
- Fix
- Available
What is CVE-2026-49853?
CVE-2026-49853 is a high-severity vulnerability in tornadoweb tornado, published on 14 Jul 2026. Any signed-in user can exploit it over the network, with no action from the victim.
Official description
Tornado is a Python web framework and asynchronous networking library. Prior to 6.5.6, SimpleAsyncHTTPClient shallow-copied redirected requests and removed only the Host header, leaving Authorization, auth_username, auth_password, and auth_mode in place when a redirect changed scheme, host, or port. This issue is fixed in version 6.5.6.
Weakness: CWE-200
Which versions are affected by CVE-2026-49853?
3 open source packages ship an affected version, including tornado.
| Package | Affected | Fixed in |
|---|---|---|
tornado PyPI | All versions | 6.5.6 |
tornado PyPI | All versions | 6.5.6 |
tornado PyPI | All versions | 6.5.6 |
How do I fix CVE-2026-49853?
Upgrade tornado to 6.5.6 or later.
Is CVE-2026-49853 being exploited?
There is no known exploitation of CVE-2026-49853 in the wild and no public exploit code.
Sources
Also known as AZL-92504, BELL-CVE-2026-49853, CLEANSTART-2026-MS01738, DEBIAN-CVE-2026-49853, ECHO-a103-ffdd-56f3, GHSA-3x9g-8vmp-wqvf and 12 more.