CVE-2026-49855
High
Description
Tornado is a Python web framework and asynchronous networking library. Prior to 6.5.6, Tornado gzip decompression routines processed limited-size chunks but did not enforce an overall limit on accumulated decompressed chunks, allowing a malicious server accessed by SimpleAsyncHTTPClient or an HTTPServer configured with decompress_request=True to consume effectively unlimited memory. This issue is fixed in version 6.5.6.
SeverityHigh
CVSS7.5
Exploit probability—
ProductTornado
PublishedJul 14, 2026
First seenJul 14, 2026
Weakness typeCWE-409CWE-409
How to fix
Update
- tornado6.5.6 or later
Affected products
| Product | Affected versions | Fixed in |
|---|---|---|
| tornadoPyPI | v < 6.5.6 | 6.5.6 |
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