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CVE-2026-49855

tornado AsyncHTTPClient accumulates decompressed chunks without size limit (gzip bomb)

Published: Jul 14, 2026Updated: Jul 16, 2026 Sources: CVE List NVDCWE-409
7.5HIGH
NVD MITRE
EPSS Score
0.6%
Top 56.2%
CISA KEV
Not in KEV
Exploits
No Known Exploits
Remediation
No Fix Available
Self-Check
OpenVAS

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.

No summary for this CVE yet.

CVSS Vector Breakdown

AV:NAC:LPR:NUI:NS:UC:NI:NA:H
Exploitability
AV:NAttack Vector
Network
AC:LAttack Complexity
Low
PR:NPrivileges Required
None
UI:NUser Interaction
None
Scope
S:UScope
Unchanged
Impact
C:NConfidentiality
None
I:NIntegrity
None
A:HAvailability
High
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Weaknesses

CWE-409

Affected Products

tornadoweb
oss-projectaka tornado
tornadoLibrary
OSS Libraries / web-framework

Exploitability

No known exploits, KEV entries, or remediation guidance available for this vulnerability yet.
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References

https://github.com/tornadoweb/tornado/security/advisories/GHSA-mgf9-4vpg-hj56
github.com
https://github.com/tornadoweb/tornado/pull/3626
github.com
https://github.com/tornadoweb/tornado/commit/ff808b33adc52d89a549376a5e3628e92abbc8ff
github.com
News mentions
1

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