CVE-2026-33532
ADVISORY - githubSummary
Parsing 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
| Version | Nesting Depth | Input Size | Result |
|---|---|---|---|
| 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 | YAMLParseError |
Depth threshold on yaml 2.8.2:
| Nesting Depth | Input Size | Result |
|---|---|---|
| 500 | 1,001 B | Parses successfully |
| 1,000 | 2,001 B | RangeError (threshold varies by stack size) |
| 5,000 | 10,001 B | RangeError |
Common Weakness Enumeration (CWE)
Uncontrolled Recursion
Uncontrolled Recursion
Unchecked Input for Loop Condition
GitHub
2.8
CVSS SCORE
4.3medium| Package | Type | OS Name | OS Version | Affected Ranges | Fix Versions |
|---|---|---|---|---|---|
| yaml | npm | - | - | >=2.0.0,<2.8.3 | 2.8.3 |
| yaml | npm | - | - | >=1.0.0,<1.10.3 | 1.10.3 |
CVSS:3 Severity and metrics
The CVSS metrics represent different qualitative aspects of a vulnerability that impact the overall score, as defined by the CVSS Specification.
The vulnerable component is bound to the network stack, but the attack is limited at the protocol level to a logically adjacent topology. This can mean an attack must be launched from the same shared physical (e.g., Bluetooth or IEEE 802.11) or logical (e.g., local IP subnet) network, or from within a secure or otherwise limited administrative domain (e.g., MPLS, secure VPN to an administrative network zone). One example of an Adjacent attack would be an ARP (IPv4) or neighbor discovery (IPv6) flood leading to a denial of service on the local LAN segment (e.g., CVE-2013-6014).
Specialized access conditions or extenuating circumstances do not exist. An attacker can expect repeatable success when attacking the vulnerable component.
The attacker requires privileges that provide basic user capabilities that could normally affect only settings and files owned by a user. Alternatively, an attacker with Low privileges has the ability to access only non-sensitive resources.
The vulnerable system can be exploited without interaction from any user.
An exploited vulnerability can only affect resources managed by the same security authority. In this case, the vulnerable component and the impacted component are either the same, or both are managed by the same security authority.
There is no loss of confidentiality.
There is no loss of trust or accuracy within the impacted component.
Performance is reduced or there are interruptions in resource availability. Even if repeated exploitation of the vulnerability is possible, the attacker does not have the ability to completely deny service to legitimate users. The resources in the impacted component are either partially available all of the time, or fully available only some of the time, but overall there is no direct, serious consequence to the impacted component.
NIST
2.8
CVSS SCORE
4.3mediumDebian
-
Red Hat
2.8
CVSS SCORE
6.5mediumChainguard
CGA-4rvw-5xqf-5m79
-