Bug 2447142 (CVE-2026-1526)

Summary: CVE-2026-1526 undici: undici: Denial of Service via unbounded memory consumption during WebSocket permessage-deflate decompression
Product: [Other] Security Response Reporter: OSIDB Bzimport <bzimport>
Component: vulnerabilityAssignee: Product Security DevOps Team <prodsec-dev>
Status: NEW --- QA Contact:
Severity: high Docs Contact:
Priority: high    
Version: unspecifiedCC: aazores, abarbaro, alizardo, anpicker, asoldano, bbaranow, bmaxwell, bparees, brian.stansberry, cmah, darran.lofthouse, dosoudil, dschmidt, eaguilar, ebaron, erezende, fjuma, hasun, istudens, ivassile, iweiss, jchui, jfula, jhe, jkoehler, jlanda, jolong, jowilson, kshier, ktsao, lphiri, mosmerov, msvehla, nboldt, nwallace, nyancey, ometelka, pberan, pesilva, pjindal, pmackay, psrna, ptisnovs, rstancel, sdawley, simaishi, smaestri, smcdonal, stcannon, syedriko, teagle, tom.jenkinson, 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 undici. A remote attacker can exploit this vulnerability by sending a specially crafted compressed frame, known as a "decompression bomb," during permessage-deflate decompression. The undici WebSocket client does not properly limit the size of decompressed data, leading to unbounded memory consumption. This can cause the Node.js process to exhaust available memory, resulting in a denial of service (DoS) where the process crashes or becomes unresponsive.
 Story Points: ---
Clone Of: Environment:
Last Closed: Type: ---
Regression: --- Mount Type: ---
Documentation: --- CRM:
Verified Versions: Category: ---
oVirt Team: --- RHEL 7.3 requirements from Atomic Host:
Cloudforms Team: --- Target Upstream Version:
Embargoed:
Bug Depends On: 2447176, 2447179, 2447181, 2447182    
Bug Blocks:    

Description OSIDB Bzimport 2026-03-12 21:01:48 UTC 
The undici WebSocket client is vulnerable to a denial-of-service attack via unbounded memory consumption during permessage-deflate decompression. When a WebSocket connection negotiates the permessage-deflate extension, the client decompresses incoming compressed frames without enforcing any limit on the decompressed data size. A malicious WebSocket server can send a small compressed frame (a "decompression bomb") that expands to an extremely large size in memory, causing the Node.js process to exhaust available memory and crash or become unresponsive.

The vulnerability exists in the PerMessageDeflate.decompress() method, which accumulates all decompressed chunks in memory and concatenates them into a single Buffer without checking whether the total size exceeds a safe threshold.