Is CVE-2026-49855 being exploited?

No public exploit is currently tracked.

How severe is CVE-2026-49855?

CVE-2026-49855 has a CVSS v3 severity of HIGH (7.5).

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CVE-2026-49855

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.