`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.
yaml is vulnerable to Stack Overflow via deeply nested YAML collections
Problem type
Affected products
eemeli
>= 2.0.0, < 2.8.3 - AFFECTED
>= 1.0.0, < 1.10.3 - AFFECTED
References
https://github.com/eemeli/yaml/security/advisories/GHSA-48c2-rrv3-qjmp
https://github.com/eemeli/yaml/commit/1e84ebbea7ec35011a4c61bbb820a529ee4f359b
https://github.com/eemeli/yaml/releases/tag/v1.10.3
https://github.com/eemeli/yaml/releases/tag/v2.8.3
GitHub Security Advisories
GHSA-48c2-rrv3-qjmp
yaml is vulnerable to Stack Overflow via deeply nested YAML collections
https://github.com/advisories/GHSA-48c2-rrv3-qjmpParsing a YAML document with yaml 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().
PoC
const YAML = require('yaml');
// ~10 KB payload: 5000 levels of nested flow sequences
const payload = '['.repeat(5000) + '1' + ']'.repeat(5000);
try {
YAML.parse(payload);
} catch (e) {
console.log(e.constructor.name); // RangeError (NOT YAMLParseError)
console.log(e.message); // Maximum call stack size exceeded
}
Test environment: Node.js v24.12.0, macOS darwin arm64
1.0.0 5,000 10,001 B RangeError 1.10.2 5,000 10,001 B RangeError 2.0.0 5,000 10,001 B RangeError 2.8.2 5,000 10,001 B RangeError 2.8.3 5,000 10,001 B YAMLParseErrorDepth threshold on yaml 2.8.2:
500 1,001 B Parses successfully 1,000 2,001 B RangeError (threshold varies by stack size) 5,000 10,001 B RangeErrorhttps://github.com/eemeli/yaml/security/advisories/GHSA-48c2-rrv3-qjmp
https://github.com/eemeli/yaml/commit/1e84ebbea7ec35011a4c61bbb820a529ee4f359b
https://github.com/eemeli/yaml/releases/tag/v1.10.3
https://github.com/eemeli/yaml/releases/tag/v2.8.3
https://github.com/advisories/GHSA-48c2-rrv3-qjmp
JSON source
https://cveawg.mitre.org/api/cve/CVE-2026-33532Click to expand
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"dateUpdated": "2026-03-26T19:49:03.842Z",
"dateReserved": "2026-03-20T18:05:11.830Z",
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},
"title": "yaml is vulnerable to Stack Overflow via deeply nested YAML collections",
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"value": "`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."
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"problemTypes": [
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"tags": [
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},
{
"url": "https://github.com/eemeli/yaml/commit/1e84ebbea7ec35011a4c61bbb820a529ee4f359b",
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},
{
"url": "https://github.com/eemeli/yaml/releases/tag/v1.10.3",
"name": "https://github.com/eemeli/yaml/releases/tag/v1.10.3",
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},
{
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"name": "https://github.com/eemeli/yaml/releases/tag/v2.8.3",
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],
"metrics": [
{
"cvssV3_1": {
"version": "3.1",
"vectorString": "CVSS:3.1/AV:N/AC:L/PR:L/UI:N/S:U/C:N/I:N/A:L",
"attackVector": "NETWORK",
"attackComplexity": "LOW",
"privilegesRequired": "LOW",
"userInteraction": "NONE",
"scope": "UNCHANGED",
"confidentialityImpact": "NONE",
"integrityImpact": "NONE",
"availabilityImpact": "LOW",
"baseScore": 4.3,
"baseSeverity": "MEDIUM"
}
}
]
}
}
}