CVE-2026-42843: Grav API Plugin privilege escalation in UsersController

CVE-2026-42843 · Severity: high · CVSS 8.8 · Published 2026-05-11

The Grav API plugin, which provides remote access to manage Grav CMS content and users, contains a flaw that allows standard users to change their own account permissions. By sending a specially crafted request, a user with basic access can grant themselves 'Super Administrator' status. This allows an attacker to take complete control of the website, including the ability to steal data, modify site content, or execute malicious code on the underlying server.

Technologies: Grav API Plugin. Vendors: Grav, Packagist.

Quick answers

Is CVE-2026-42843 exploited in the wild?
No. Junglewise Threat Intelligence has no report of CVE-2026-42843 being exploited in the wild.
How severe is CVE-2026-42843?
High severity, with a CVSS score of 8.8, published 11 May 2026.
Which products and versions are affected?
Grav API Plugin < 1.0.0-beta.15, Prior to 1.0.0-beta.15; getgrav/grav-plugin-api (Packagist) < 1.0.0-beta.15, ECOSYSTEM:introduced=0,fixed=1.0.0-beta.15.
Is there a fix for CVE-2026-42843?
Yes. getgrav/grav-plugin-api (Packagist): upgrade to 1.0.0-beta.15 or later. Junglewise finds every place you run it, drafts the upgrade and applies it once you approve.
How is CVE-2026-42843 attacked?
It is attacked over the network, in a software library.
Am I affected by CVE-2026-42843?
Check whether you run Grav API Plugin or getgrav/grav-plugin-api (Packagist) at an affected version. Junglewise does that check for you around the clock: connect your code, cloud and domains, and it matches new vulnerabilities like this one against what you actually run and tells you when one reaches you.

How to fix

  • getgrav/grav-plugin-api (Packagist): upgrade to 1.0.0-beta.15 or later
    composer require getgrav/grav-plugin-api:^1.0.0-beta.15

Technical details

An insecure direct object reference (IDOR) and logic flaw exist in the `UsersController::update` method of the Grav API plugin. While the plugin allows users to update their own profiles with basic `api.access` permissions, the `$allowedFields` whitelist indiscriminately includes the 'access' field. An attacker can submit a PATCH request to the `/api/v1/users/{username}` endpoint containing a malicious 'access' object. This allows a low-privileged user to grant themselves `admin.super` and `api.super` permissions, leading to full system compromise and potential Remote Code Execution (RCE) via template manipulation. The issue is fixed in version 1.0.0-beta.15.

Affected products

  • Grav Grav API Plugin Prior to 1.0.0-beta.15

Identifiers

  • CVE-2026-42843
  • GHSA-r945-h4vm-h736

Timeline

  • 2026-04-27: advisory: GitHub Security Advisory published by vendor
  • 2026-05-11: disclosed: CVE published to NVD

References

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