CVE-2021-25915 is a critical-severity (CVSS 9.8) CWE-1321 vulnerability in changeset. 1 public exploit reference exists, so weaponization risk is real. A fix is available for changeset — see the affected versions and patch details below.
Changeset vulnerable to prototype pollution
Exploitation Status
Proof-of-concept exploit code exists
- CISA’s SSVC triage found public proof-of-concept exploit code for this CVE, though no confirmed active exploitation.
- CISA assesses this as automatable — exploitation doesn’t require manual, per-target effort, which raises the odds of mass scanning and opportunistic attacks.
- A successful exploit gives an attacker total control of the affected component, not partial access.
Exploitation and automatability from CISA’s SSVC triage for CVE-2021-25915.
EPSS Exploitation Probability
EPSS (Exploit Prediction Scoring System) is a daily probability model maintained by FIRST.org. It estimates the likelihood a CVE will be exploited in production environments within the next 30 days, derived from real-world threat intelligence signals.
How urgent is this, really
CVE-2021-25915 plotted by exploitation likelihood (EPSS) against impact (CVSS). The shaded corner — EPSS 50%+ and CVSS 7.0+ — is where this CVE doesn't sit, though severity or exploitability alone can still warrant action.
Where this sits among everything scored
Of 378,156 CVEs with a current EPSS score, this one falls in the < 10% band (highlighted). Real counts from FIRST.org, not a sample — log-scaled since the landscape is heavily right-skewed.
Real-World Exposure
How broadly this vulnerability is actually deployed: weekly install volume shows current usage, and reverse-dependency count shows how many other packages break if it stays unpatched.
changesetnpmDescription
Overview
Prototype pollution vulnerability in 'changeset' versions 0.0.1 through 0.2.5 allows attackers to cause a denial of service and may lead to remote code execution.
Details
The npm module 'changeset' can be abused by Prototype Pollution vulnerability since the function 'apply()' does not check for the type of object before assigning value to the property. Due to this flaw an attacker could create a non-existent property or able to manipulate the property which leads to Denial of Service or potentially Remote code execution.
PoC Details
The 'apply()' function accepts 'changes, target, modify' as argument. Due to the absence of validation on the values passed into the 'changes' argument, an attacker can supply a malicious value by adjusting the value to include the 'proto' property. Since there is no validation before assigning the property to check whether the assigned argument is the Object's own property or not, the property 'polluted' will be directly be assigned to the new object thereby polluting the Object prototype. Using the example below, if there is a check to validate 'polluted' the valued later in the code, it would be substituted as "Yes! Its Polluted" as it had been polluted.
PoC Code
var changeset = require("changeset") const patch = [{
type: 'put',
key: ["__proto__", "polluted"],
value: "Yes! Its Polluted"
}];
console.log("Before : " + {}.polluted);
changeset.apply(patch, {}, true);
console.log("After : " + {}.polluted);
Affected Packages
| Ecosystem | Package | Vulnerable range | Fix |
|---|---|---|---|
| 📦npm | changeset | ≥ 0.0.1&&< 0.2.5 | 0.2.5npm install changeset@0.2.5 |
Research use only. For defensive security, authorized penetration testing, and academic research only. Never execute exploit code against systems without explicit written authorization.
Detection & mitigation playbook
Open-source dependencyDetect
Scan your dependency tree (package-lock.json, pnpm-lock.yaml, requirements.txt, go.sum, etc.) for changeset, including transitive dependencies — a direct dependency you never call can still pull in a vulnerable version.
Fix
Update changeset to 0.2.5 or later, then make sure no transitive (indirect) dependency still pins the vulnerable range — O3 confirms CVE-2021-25915 is resolved across your whole dependency graph.
Workarounds
If you can't upgrade right away: gate or disable the affected feature, validate untrusted input at the boundary, and avoid passing attacker-controlled data into the vulnerable path. O3's runtime protection blocks exploitation in production as an interim safeguard until the upgrade lands.
How O3 protects you
O3 Security's impact-aware SCA analyses which vulnerable code paths your application actually calls, so a match like CVE-2021-25915 can be triaged on real exposure rather than presence alone.
Tailored to CVE-2021-25915. Runtime protection reduces exposure until a permanent patch is applied and verified — it complements patching, it doesn't replace it.
Frequently Asked Questions
Is CVE-2021-25915 in your dependencies?
O3 Security finds CVE-2021-25915 across npm dependencies, including transitive ones, and its impact-aware SCA ranks findings by whether your code actually calls the vulnerable path.