Bug 2527118 (CVE-2026-84375)

Summary:	CVE-2026-84375 js-yaml: js-yaml: Denial of Service vulnerability in YAML parsing
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:	aadhikar, aazores, abarbaro, abuckta, akhatavk, akostadi, alizardo, amasferr, amctagga, anjoseph, anpicker, anthomas, anujha, aoconnor, aos-team-art-private, aruklets, aschwart, asdas, asoldano, aszczucz, ataylor, bbaranow, bbrownin, bmaxwell, bniver, boliveir, bparees, brasmith, bsmejkal, bstansbe, cdrage, cmah, cochase, dbruscin, dfreiber, dkeler, dkuc, dlofthou, dmayorov, doconnor, dpaolell, dranck, drichtar, drow, dschmidt, dymurray, eaguilar, ebaron, eborisov, ehelms, ehugonne, ewittman, flucifre, fmariani, gbenhaim, ggainey, gmalinko, gmeno, gotiwari, gparvin, groman, hasun, ibolton, istudens, ivassile, iweiss, jachapma, janstey, jburrell, jchui, jdelft, jfula, jhe, jhorak, jlanda, jlledo, jmatsuok, jmatthew, jmontleo, jowilson, jpasqual, jprabhak, jtolenti, jupierce, juwatts, jwong, jwon, kaycoth, kshier, ktsao, kvanderr, lball, lchilton, lgarciaa, mbenjamin, mbiarnes, mcarlett, mdellweg, mhackett, mhulan, mosmerov, mposolda, mreynolds, mstipich, msvehla, mvyas, nboldt, ngough, nipatil, niyer, nmoumoul, nwallace, nyancey, oaljalju, omaciel, ometelka, orabin, osousa, pantinor, pberan, pcreech, pdelbell, pesilva, pgaikwad, pjindal, pmackay, ppalepu, ppostler, prdhamdh, progier, psrna, ptisnovs, rchan, rexwhite, rhaigner, rhel-process-autobot, rjohnson, rkubis, rmartinc, rstancel, rstepani, rushinde, sdawley, sfeifer, sghai, sidsharm, simaishi, slucidi, smallamp, snegrini, sostapov, spichugi, sseago, ssilvert, stcannon, sthirugn, sthorger, suppawar, syedriko, tbordaz, tcunning, teagle, thason, thjenkin, tmalecek, tsedmik, ttakamiy, twaugh, vashirov, vdosoudi, vereddy, veshanka, vkumar, vlaad, vmuzikar, watson-tool-maintainers, wtam, xdharmai, yfang, yguenane
Target Milestone:	---	Keywords:	Security
Target Release:	---
Hardware:	All
OS:	Linux
Whiteboard:
Fixed In Version:		Doc Type:	---
Doc Text:	A flaw was found in js-yaml, a JavaScript YAML parser. An attacker can exploit this by providing a specially crafted YAML document that causes the parser to perform excessive processing when handling merge keys with empty sources. This can lead to prolonged CPU consumption, effectively causing a denial of service (DoS) for applications that process untrusted YAML input.	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:

Description OSIDB Bzimport 2026-09-01 21:51:53 UTC

js-yaml is a JavaScript YAML parser and dumper. From 3.0.0 until 3.15.2 and 4.3.2, maxTotalMergeKeys in lib/js-yaml/loader.js and lib/loader.js does not count empty mapping sources while processing the merge key <<. An attacker can alias a large sequence of empty mappings into many merge targets, causing O(N * K) processing while totalMergeKeys remains unchanged and the configured resource limit is never reached. A relatively small YAML document can therefore cause prolonged CPU consumption in applications that parse untrusted YAML, and merge processing is enabled by default on these release lines. This issue is fixed in versions 3.15.2 and 4.3.2.