Bug 2500686 (CVE-2026-49855)

Summary:	CVE-2026-49855 tornado: Tornado: Denial of Service via uncontrolled gzip decompression memory consumption
Product:	[Other] Security Response	Reporter:	OSIDB Bzimport <bzimport>
Component:	vulnerability	Assignee:	Product Security DevOps Team <prodsec-dev>
Status:	NEW ---	QA Contact:
Severity:	high	Docs Contact:
Priority:	high
Version:	unspecified	CC:	akhatavk, anpicker, aos-team-art-private, asdas, bbrownin, bparees, dpaolell, dschmidt, ebourniv, eglynn, hasun, jdelft, jfula, jjoyce, jlanda, jowilson, jpretori, jschluet, jupierce, jwong, kaycoth, kshier, lgarciaa, lhh, mbiarnes, mburns, mgarciac, nyancey, omaciel, ometelka, ppalepu, ppostler, prdhamdh, ptisnovs, rhel-process-autobot, rjohnson, sbunciak, sghai, sidsharm, simaishi, stcannon, suppawar, syedriko, teagle, ttakamiy, vlaad, watson-tool-maintainers, xdharmai, yguenane
Target Milestone:	---	Keywords:	Security
Target Release:	---
Hardware:	All
OS:	Linux
Whiteboard:
Fixed In Version:		Doc Type:	---
Doc Text:	A flaw was found in Tornado, a Python web framework and asynchronous networking library. Its gzip decompression routines process data in limited-size chunks but do not enforce an overall limit on the total accumulated decompressed data. This vulnerability allows a malicious server to consume effectively unlimited memory, leading to a denial of service, when accessed by a client using SimpleAsyncHTTPClient or an HTTPServer configured with decompress_request set to true.	Story Points:	---
Clone Of:		Environment:
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Documentation:	---	CRM:
Verified Versions:		Category:	---
oVirt Team:	---	RHEL 7.3 requirements from Atomic Host:
Cloudforms Team:	---	Target Upstream Version:
Embargoed:
Bug Depends On:	2522080, 2522081, 2522082
Bug Blocks:

Description OSIDB Bzimport 2026-07-14 21:05:08 UTC

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.

Comment 2 Jon Orris 2026-09-14 13:33:47 UTC

This issue has been addressed in the following products:

  Red Hat Enterprise Linux 10

Via RHSA-2026:67147 https://access.redhat.com/errata/RHSA-2026:67147

Comment 3 Jon Orris 2026-09-14 13:38:10 UTC

This issue has been addressed in the following products:

  Red Hat Enterprise Linux 9

Via RHSA-2026:67146 https://access.redhat.com/errata/RHSA-2026:67146