CVE-2026-48170: scimPatch vulnerable to prototype pollution via unfiltered keys in patch

Should you act?

Critical, preconditions apply

Severe if exploited, but exploitation needs conditions that may not apply to you. This signal is computed from CISA KEV, EPSS and CVSS data; it is not an editorial verdict.

• Not in CISA KEV, but CISA’s SSVC assessment records a public proof-of-concept, so attack code exists.
• EPSS 0.4%, percentile 33: FIRST’s model estimates a 0.4% chance of exploitation activity in the next 30 days, higher than 33% of all scored CVEs (low). EPSS is a probability, not a verdict.
• Needs an account (low (any account)). Exposure depends on who can log in.
• Only applies if your dependency tree includes scim-patch (npm) <= 0.9.0, fixed in 0.9.1. Check your lockfile, including transitive dependencies.

What it is

scim-patch, a library to perform SCIM patch, prior to version 0.9.1 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. Version 0.9.1 contains a patch. A workaround is available. 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.

From the GitHub advisory

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:

Weakness type: CWE-1321.

Product: scim-patch (npm) · Assigned by: GitHub_M · Published: 2026-08-07

Affected and fixed versions

Severity scores

• Attack vector: network (remotely reachable)
• Attack complexity: low
• Privileges required: low (any account)
• User interaction: none
• Scope: changed (can affect other components)

CVSS measures how bad a flaw is if exploited, not how likely exploitation is. Read it next to the exploitation data below.

Exploitation and urgency

• CISA KEV: not listed (no confirmed in-the-wild exploitation known to CISA).
• CISA SSVC assessment: exploitation poc, automatable no, technical impact partial.
• FIRST EPSS (model of 2026-10-21): 0.40% probability of exploitation activity in the next 30 days; percentile 33.

Timeline

• 2026-06-22 — GitHub-reviewed advisory GHSA-9m6g-wc8r-q59c published (critical)
• 2026-08-07 — CVE record published by GitHub_M
• 2026-08-10 — CVE record last updated

Sources and references

Original sources first. Version and fix details should always be confirmed against the vendor or project advisory.

Vulnerability records

1. GitHub Advisory GHSA-9m6g-wc8r-q59c github.com
2. CVE.org record CVE-2026-48170 cve.org
3. NVD entry CVE-2026-48170 nvd.nist.gov

Other references from the CVE record and advisory

1. github.com github.com
2. github.com github.com

Critical npm advisories · Today’s Security Digest