CVE-2025-64718

js-yaml has prototype pollution in merge (<<)

MEDIUM
5.3
CVSS Score
Published: November 13, 2025 at 03:32 PM UTC
Updated: October 7, 2026 at 09:10 PM UTC
1 product affected across 1 vendorJs Yaml

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Severity
MEDIUM5.3
Exploit prediction
EPSS 0.4%
SSVC
No known exploit

Description

js-yaml is a JavaScript YAML parser and dumper. In js-yaml 4.1.0 and below, it's possible for an attacker to modify the prototype of the result of a parsed yaml document via prototype pollution (`__proto__`). All users who parse untrusted yaml documents may be impacted. The problem is patched in js-yaml 4.1.1. Users can protect against this kind of attack on the server by using `node --disable-proto=delete` or `deno` (in Deno, pollution protection is on by default).

Affected

Our own answer: ranges merged, affected separated from platform-only, with confidence and review flags.

v < 3.14.2v < 4.1.14.0.0 ≤ v < 4.1.1
Affected range stops below 3.14.2, so it looks safe — our inference, not a vendor statement
Affected range stops below 4.1.1, so it looks safe — our inference, not a vendor statement

References (5)

SSVC — Action Prioritization

SSVCNo known exploitAutomatablePartial impact

SSVC signals action urgency (what to patch first), separate from CVSS which measures severity.

CVSS

5.3MEDIUMGitHub_M
Attack Vector
NETWORK
Complexity
LOW
Privileges
NONE
User Interaction
NONE
Scope
UNCHANGED
Confidentiality
NONE
Integrity
LOW
Availability
NONE
Vector?

Quick Info

StatusANALYZED
CWE
CWE-1321

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