---
title: "CVE-2026-28794: `@orpc/client` has Prototype Pollution via `StandardRPCJsonSerializer` Deserialization"
url: https://erroneo.us/security/cve/CVE-2026-28794/
description: "CVE-2026-28794 (@orpc/client (npm)): oRPC is an tool that helps build APIs that are end-to-end type-safe and adhere to OpenAPI standards. Prior to version…"
type: vulnerability-record
section: "Security Digest"
date_published: 2026-03-06
date_modified: 2026-03-09
publisher: erroneo.us
author: erroneo.us Security Desk
cve: "CVE-2026-28794"
kev: false
cvss: 9.3
epss: 0.01252
license: All rights reserved. Quote with attribution and a link.
---

# CVE-2026-28794: `@orpc/client` has Prototype Pollution via `StandardRPCJsonSerializer` Deserialization

**Signal:** Critical and remotely reachable. No known exploitation yet, but it is network-reachable without credentials. (Computed from CISA KEV, EPSS and CVSS; not an editorial verdict.)

## Should you act?

- Not in CISA KEV , but CISA’s SSVC assessment records a public proof-of-concept, so attack code exists.
- EPSS 1.3% , percentile 69: FIRST’s model estimates a 1.3% chance of exploitation activity in the next 30 days, higher than 69% of all scored CVEs (moderate). EPSS is a probability, not a verdict.
- Remotely reachable with no login and no user interaction. If the vulnerable service is exposed to the internet, prioritize it.
- Only applies if your dependency tree includes @orpc/client (npm) <= 1.13.5, fixed in 1.13.6 . Check your lockfile, including transitive dependencies.

## What it is

oRPC is an tool that helps build APIs that are end-to-end type-safe and adhere to OpenAPI standards. Prior to version 1.13.6, a prototype pollution vulnerability exists in the RPC JSON deserializer of the @orpc/client package. The vulnerability allows unauthenticated, remote attackers to inject arbitrary properties into the global Object.prototype. Because this pollution persists for the lifetime of the Node.js process and affects all objects, it can lead to severe security breaches, including authentication bypass, denial of service, and potentially Remote Code Execution. This issue has been patched in version 1.13.6.

## Affected packages

- npm `@orpc/client` <= 1.13.5 → fixed: 1.13.6

## Affected products (CVE record)

- middleapi orpc: < 1.13.6

## Severity

- GitHub_M CVSS 4.0: 9.3 `CVSS:4.0/AV:N/AC:L/AT:N/PR:N/UI:N/VC:H/VI:H/VA:H/SC:L/SI:L/SA:N`
- GitHub CVSS 4.0: 9.3 `CVSS:4.0/AV:N/AC:L/AT:N/PR:N/UI:N/VC:H/VI:H/VA:H/SC:L/SI:L/SA:N`

## Exploitation

- CISA KEV: not listed (no confirmed in-the-wild exploitation known to CISA).
- CISA SSVC assessment: exploitation poc , automatable yes , technical impact total .
- FIRST EPSS (model of 2026-10-21): 1.25% probability of exploitation activity in the next 30 days; percentile 69.

## Sources

- [GitHub Advisory GHSA-m272-9rp6-32mc](https://github.com/advisories/GHSA-m272-9rp6-32mc)
- [CVE.org record CVE-2026-28794](https://www.cve.org/CVERecord?id=CVE-2026-28794)
- [NVD entry CVE-2026-28794](https://nvd.nist.gov/vuln/detail/CVE-2026-28794)
- [github.com](https://github.com/middleapi/orpc/security/advisories/GHSA-m272-9rp6-32mc)
- [github.com](https://github.com/middleapi/orpc/commit/1dba06fc6f938c2486de303c2fa096bc1c8418b5)

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Source page: https://erroneo.us/security/cve/CVE-2026-28794/ · Security Digest: https://erroneo.us/security/ · More: https://erroneo.us/llms.txt