Bug 2451858 (CVE-2026-33532)

Summary:	CVE-2026-33532 yaml: yaml: Denial of Service via deeply nested YAML document parsing
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, akostadi, alcohan, alizardo, amasferr, anthomas, aschwart, asoldano, ataylor, bbaranow, bbrownin, bdettelb, bmaxwell, boliveir, brasmith, bstansbe, caswilli, chfoley, cmyers, cochase, dbruscin, dlofthou, dmayorov, dnakabaa, doconnor, dranck, drosa, dschmidt, ehelms, erezende, ewittman, fdeutsch, ggainey, gmalinko, gparvin, istudens, ivassile, iweiss, janstey, jbalunas, jchui, jhe, jkoehler, jlanda, jlledo, juwatts, jvasik, jwong, kaycoth, kshier, ktsao, kvanderr, lchilton, lcouzens, lphiri, manissin, mhulan, mnovotny, mosmerov, mposolda, msvehla, nboldt, nipatil, nmoumoul, nwallace, omaciel, oramraz, osousa, pahickey, pantinor, pberan, pbizzarr, pcreech, pdelbell, pesilva, pjindal, pmackay, psrna, rblanco, rchan, rgodfrey, rhaigner, rkubis, rmartinc, rstancel, rstepani, sausingh, sdawley, sfeifer, simaishi, smaestri, smallamp, smcdonal, smullick, ssilvert, stcannon, sthorger, stirabos, swoodman, teagle, thason, thjenkin, tmalecek, tsedmik, ttakamiy, vdosoudi, vmugicag, vmuzikar, yguenane
Target Milestone:	---	Keywords:	Security
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Hardware:	All
OS:	Linux
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Doc Text:	A flaw was found in `yaml`, a YAML parser and serializer for JavaScript. An attacker who can supply a specially crafted, deeply nested YAML document for parsing can trigger a `RangeError` due to a stack overflow. This can lead to a Denial of Service (DoS) by exhausting the call stack, potentially causing the application to fail requests or terminate the Node.js process.	Story Points:	---
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oVirt Team:	---	RHEL 7.3 requirements from Atomic Host:
Cloudforms Team:	---	Target Upstream Version:
Embargoed:

Description OSIDB Bzimport 2026-03-26 20:03:08 UTC

`yaml` is a YAML parser and serialiser for JavaScript. Parsing a YAML document with a version of `yaml` on the 1.x branch prior to 1.10.3 or on the 2.x branch prior to 2.8.3 may throw a RangeError due to a stack overflow. The node resolution/composition phase uses recursive function calls without a depth bound. An attacker who can supply YAML for parsing can trigger a `RangeError: Maximum call stack size exceeded` with a small payload (~2–10 KB). The `RangeError` is not a `YAMLParseError`, so applications that only catch YAML-specific errors will encounter an unexpected exception type. Depending on the host application's exception handling, this can fail requests or terminate the Node.js process. Flow sequences allow deep nesting with minimal bytes (2 bytes per level: one `[` and one `]`). On the default Node.js stack, approximately 1,000–5,000 levels of nesting (2–10 KB input) exhaust the call stack. The exact threshold is environment-dependent (Node.js version, stack size, call stack depth at invocation). Note: the library's `Parser` (CST phase) uses a stack-based iterative approach and is not affected. Only the compose/resolve phase uses actual call-stack recursion. All three public parsing APIs are affected: `YAML.parse()`, `YAML.parseDocument()`, and `YAML.parseAllDocuments()`. Versions 1.10.3 and 2.8.3 contain a patch.