Bug 2553726 (CVE-2026-87029)

Summary: CVE-2026-87029 undici: undici: Denial of Service via unhandled exception in decompress interceptor
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 remote malicious or compromised HTTP server can cause a Denial of Service (DoS) by sending a small compressed response that decompresses beyond configured size limits. Because undici fails to catch errors triggered by response handlers during decompression, an unhandled exception is produced that crashes the client application.
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Description OSIDB Bzimport 2026-10-15 19:23:50 UTC 
undici is an HTTP client library for Node.js. In versions 7.15.0 through 7.30.0 and 8.0.0 through 8.12.1, its decompress interceptor forwards decompressed response data to the downstream handler from zlib stream event callbacks without catching exceptions those callbacks may throw, and while undici's engine converts a synchronous throw from a downstream handler into a per-request failure, that protection is absent when the throw happens asynchronously from a zlib callback. As a result, a downstream handler that throws by design, such as the built-in dump interceptor which throws when a response exceeds its configured maximum size, escapes as an uncaught exception that terminates the Node.js process. A malicious or compromised HTTP server can crash any client that composes the decompress interceptor with such a handler by returning a small compressed body that decompresses to more than the configured limit, so only the decompressed size matters and the bytes on the wire stay tiny. The issue is fixed in undici 7.30.1 and 8.12.2, and users should upgrade to one of those versions or later. As a workaround, avoid composing the decompress interceptor with a response handler that throws during response processing until upgrading.