Bug 2528772 (CVE-2026-84890)

Summary:	CVE-2026-84890 undici: undici: Denial of Service via unbounded decompression of compressed responses
Product:	[Other] Security Response	Reporter:	OSIDB Bzimport <bzimport>
Component:	vulnerability	Assignee:	Product Security DevOps Team <prodsec-dev>
Status:	NEW ---	QA Contact:
Severity:	medium	Docs Contact:
Priority:	medium
Version:	unspecified	CC:	abarbaro, akhatavk, alizardo, aos-team-art-private, asdas, ataylor, cdrage, dbruscin, dpaolell, dschmidt, eborisov, ehugonne, gbenhaim, gtanzill, jbuscemi, jchui, jdelft, jhe, jlanda, jupierce, kshier, ktsao, kvanderr, lball, lchilton, lgarciaa, mbiarnes, mstipich, nboldt, ngough, niyer, oaljalju, ppalepu, ppostler, prdhamdh, psrna, rexwhite, rhel-process-autobot, rushinde, sdawley, sfeifer, sghai, sidsharm, simaishi, stcannon, sthirugn, suppawar, teagle, twaugh, veshanka, vlaad, watson-tool-maintainers, yguenane
Target Milestone:	---	Keywords:	Security
Target Release:	---
Hardware:	All
OS:	Linux
Whiteboard:
Fixed In Version:		Doc Type:	---
Doc Text:	A flaw was found in undici. The decompress interceptor in undici processes compressed response bodies based on the untrusted Content-Encoding header. A remote attacker can exploit this by sending a small, specially crafted compressed payload, known as a 'compression bomb,' which expands significantly in client memory. This unbounded decompression can lead to memory exhaustion and cause the application to crash, resulting in a Denial of Service (DoS).	Story Points:	---
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Verified Versions:		Category:	---
oVirt Team:	---	RHEL 7.3 requirements from Atomic Host:
Cloudforms Team:	---	Target Upstream Version:
Embargoed:
Bug Depends On:	2530853, 2530854, 2530855, 2530852
Bug Blocks:

Description OSIDB Bzimport 2026-09-04 17:29:55 UTC

undici's decompress interceptor decompresses response bodies according to the untrusted Content-Encoding header. While the number of content-encoding layers is capped, the total decompressed output size is unbounded and there is no configuration option to limit it. A malicious or faulty upstream can therefore return a small compressed payload, a compression bomb, that expands to hundreds of megabytes or more in client memory, an asymmetric resource consumption that can exhaust memory and crash the process. This affects undici versions from 7.15.0 up to 7.29.1 and from 8.0.0 up to 8.10.2. Users should upgrade to undici 7.29.1 or 8.10.2.