Bug 2553663 (CVE-2026-109924)

Summary: CVE-2026-109924 undici: undici: Denial of Service via memory exhaustion in EventSource client
Product: [Other] Security Response Reporter: OSIDB Bzimport <bzimport>
Component: vulnerabilityAssignee: Product Security DevOps Team <prodsec-dev>
Status: NEW --- QA Contact:
Severity: medium Docs Contact:
Priority: medium    
Version: unspecifiedCC: aazores, abarbaro, akhatavk, alizardo, aos-team-art-private, asdas, ataylor, cdrage, cmah, csuconic, dbruscin, dpaolell, dschmidt, eaguilar, ebaron, eborisov, gbenhaim, gtanzill, gtully, ikhan, jbuscemi, jchui, jdelft, jhe, jlanda, jmatsuok, jsherman, jtolenti, jupierce, kshier, ktsao, kvanderr, lball, lchilton, lgarciaa, mbiarnes, mstipich, nboldt, ngough, niyer, oaljalju, pjindal, ppalepu, ppostler, prdhamdh, psrna, rbobbitt, rexwhite, rgemmell, rgodfrey, rhel-process-autobot, rushinde, sdawley, sfeifer, sghai, sidsharm, simaishi, stcannon, sthirugn, suppawar, tbish, tlavocat, twaugh, veshanka, vlaad, watson-tool-maintainers, yguenane
Target Milestone: ---Keywords: Security
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Hardware: All   
OS: Linux   
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A flaw was found in undici. A malicious server can trigger a Denial of Service (DoS) by exhausting application memory. When an application connects to an untrusted Server-Sent Events (SSE) feed, the EventSource parser does not properly limit retained internal state when processing fragmented lines or repeated message fields. This allows an attacker to send crafted or compressed responses that consume excessive memory and terminate the application process.
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oVirt Team: --- RHEL 7.3 requirements from Atomic Host:
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Description OSIDB Bzimport 2026-10-15 18:35:15 UTC 
undici is an HTTP client library for Node.js. In versions 6.5.0 through 6.29.0, 7.0.0 through 7.30.0, and 8.0.0 through 8.12.1, its EventSource client can be driven to exhaust process memory by a malicious or compromised Server-Sent Events peer. By sending millions of tiny completed data fields with no blank event separator, or a single unfinished line split across many chunks, the parser retains a growing amount of per-field and per-chunk state that the byte-based maxEventSize and maxResponseSize limits do not bound, and because maxResponseSize is enforced on the compressed body before decompression, a small compressed response can expand into enough retained memory to terminate the process. An application only needs to maintain an EventSource connection to an untrusted peer, which controls only the response, and availability is the only impact. The issue is fixed in undici 6.29.1, 7.30.1, and 8.12.2, which bound the retained parser state independently of the byte limits, and users should upgrade to one of those versions or later. There is no workaround.