Vulnerability-Lookup

CVE-2026-42609 (GCVE-0-2026-42609)

Vulnerability from cvelistv5 – Published: 2026-05-11 15:03 – Updated: 2026-05-14 17:56

Title

Grav: Administrative Account Disruption and Privilege De-escalation via User Overwrite Logic

Summary

Grav is a file-based Web platform. Prior to 2.0.0-beta.2, a business logic vulnerability in the Grav Admin Panel allows a low-privileged user (with only user creation permissions) to overwrite existing accounts, including the primary administrator. By creating a new user with a username that already exists, the system updates the existing account's metadata and permissions instead of rejecting the request. This leads to a Denial of Service (DoS) on administrative functions and Privilege De-escalation of the root account. This vulnerability is fixed in 2.0.0-beta.2.

Severity ?

8.1 (High)


                        
                          CVSS:3.1/AV:N/AC:L/PR:L/UI:N/S:U/C:N/I:H/A:H

CWE

CWE-269 - Improper Privilege Management
CWE-285 - Improper Authorization
CWE-639 - Authorization Bypass Through User-Controlled Key
CWE-837 - Improper Enforcement of a Single, Unique Action

Assigner

GitHub_M

References

4 references

URL	Tags
https://github.com/getgrav/grav/security/advisori…	x_refsource_CONFIRM
https://github.com/getgrav/grav/commit/5a12f9be83…	x_refsource_MISC
https://github.com/getgrav/grav/commit/c66dfeb5ff…	x_refsource_MISC
https://github.com/getgrav/grav/commit/d904efc33e…	x_refsource_MISC

Impacted products

1 product

Vendor	Product	Version
getgrav	grav	Affected: < 2.0.0-beta.2

Show details on NVD website

JSON

To clipboard

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FKIE_CVE-2026-42609

Vulnerability from fkie_nvd - Published: 2026-05-11 16:17 - Updated: 2026-05-14 18:16

Severity ?

8.1 (High) - CVSS:3.1/AV:N/AC:L/PR:L/UI:N/S:U/C:N/I:H/A:H

Summary

References

URL	Tags
security-advisories@github.com	https://github.com/getgrav/grav/commit/5a12f9be8314682c8713e569e330f11805d0a663	Patch
security-advisories@github.com	https://github.com/getgrav/grav/commit/c66dfeb5ff679a1667678c6335eb9ff3255dfc47	Patch
security-advisories@github.com	https://github.com/getgrav/grav/commit/d904efc33e03ebb597afde8d3368b28cf0423632	Patch
security-advisories@github.com	https://github.com/getgrav/grav/security/advisories/GHSA-rr73-568v-28f8	Exploit, Patch, Vendor Advisory
134c704f-9b21-4f2e-91b3-4a467353bcc0	https://github.com/getgrav/grav/security/advisories/GHSA-rr73-568v-28f8	Exploit, Patch, Vendor Advisory

Impacted products

	Vendor	Product	Version
	getgrav	grav	*
	getgrav	grav	2.0.0

JSON

To clipboard

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GHSA-RR73-568V-28F8

Vulnerability from github – Published: 2026-05-05 21:29 – Updated: 2026-05-13 13:52

Summary

Grav Vulnerable to Administrative Account Disruption and Privilege De-escalation via User Overwrite Logic

Details

Summary

A business logic vulnerability in the Grav Admin Panel allows a low-privileged user (with only user creation permissions) to overwrite existing accounts, including the primary administrator. By creating a new user with a username that already exists, the system updates the existing account's metadata and permissions instead of rejecting the request. This leads to a Denial of Service (DoS) on administrative functions and Privilege De-escalation of the root account.

Details

The vulnerability stems from an insecure "Create or Update" logic within the user management module. When the admin-addon handles a user creation request, it does not strictly validate whether the username is already taken by a higher-privileged account. Instead of returning a "409 Conflict" or a validation error, the application logic proceeds to overwrite the existing user configuration file (e.g., user/accounts/root0.yaml) with the new, lower-privileged data provided by the attacker. Because the attacker cannot assign higher permissions to themselves (due to existing fixes), the result is that the targeted account (the original Admin/Root) has its access levels wiped or replaced by the attacker's input, effectively locking the real administrator out of the system.

PoC

Log in as a Super User (e.g., root0) and create a low-privileged user (e.g., adminuser).
Assign adminuser the following specific permissions: admin.login admin.users.list admin.users.read admin.users.create
Log out and log back in as adminuser.
Navigate to User Accounts -> Add.
Fill in the form with the following details: Username: root0 (The exact username of the Super User) Email: anything@grav.f Fullname: Fake Root0
Click Save.
Observe that the account is successfully "created".
The original administrative permissions are gone, and the account is now restricted.

PoC video

https://github.com/user-attachments/assets/047cb44e-0279-402b-b4fb-12bf5d427a5e

Impact

This is a Privilege De-escalation and Account Disruption vulnerability. Who is impacted: Any Grav installation where a non-admin user is granted permission to create other users. Consequence: An attacker can effectively disable all administrative accounts on the platform, leading to a complete loss of management control over the CMS.

Maintainer note — fix applied (2026-04-24)

Fixed in Grav core on the 2.0 branch: commit d904efc33 — will ship in 2.0.0-beta.2.

What changed: UserObject::save already had a uniqueness guard (commit 19c2f8da7, November 2025) that blocks the PoC. This release tightens that guard:

strpos($key, '@@') → str_contains($key, '@@'). The previous form was falsy when the transient-key marker was at position 0 (e.g. @@hash), silently bypassing the check. str_contains returns a proper boolean.
The instanceof FileStorage gate was dropped so the uniqueness check runs for any FlexStorageInterface backend — not just the default file-per-user YAML one.

A low-privileged user with admin.users.create can no longer disrupt a super-admin account by submitting that admin's username through the "add user" form.

Files: - system/src/Grav/Common/Flex/Types/Users/UserObject.php. - tests/unit/Grav/Common/Security/UserOverwriteSecurityTest.php — 3 tests pinning the PoC, the @@-prefix edge case, and pass-through for free usernames.

Severity ?

8.1 (High)


                  
                    CVSS:3.1/AV:N/AC:L/PR:L/UI:N/S:U/C:N/I:H/A:H

Show details on source website

JSON

To clipboard

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            },
            {
              "fixed": "2.0.0-beta.2"
            }
          ],
          "type": "ECOSYSTEM"
        }
      ]
    }
  ],
  "aliases": [
    "CVE-2026-42609"
  ],
  "database_specific": {
    "cwe_ids": [
      "CWE-269",
      "CWE-285",
      "CWE-639",
      "CWE-837"
    ],
    "github_reviewed": true,
    "github_reviewed_at": "2026-05-05T21:29:53Z",
    "nvd_published_at": "2026-05-11T16:17:33Z",
    "severity": "HIGH"
  },
  "details": "### Summary\nA business logic vulnerability in the Grav Admin Panel allows a low-privileged user (with only user creation permissions) to overwrite existing accounts, including the primary administrator. By creating a new user with a username that already exists, the system updates the existing account\u0027s metadata and permissions instead of rejecting the request. This leads to a Denial of Service (DoS) on administrative functions and Privilege De-escalation of the root account.\n\n### Details\nThe vulnerability stems from an insecure \"Create or Update\" logic within the user management module. When the admin-addon handles a user creation request, it does not strictly validate whether the username is already taken by a higher-privileged account. Instead of returning a \"409 Conflict\" or a validation error, the application logic proceeds to overwrite the existing user configuration file (e.g., user/accounts/root0.yaml) with the new, lower-privileged data provided by the attacker.\nBecause the attacker cannot assign higher permissions to themselves (due to existing fixes), the result is that the targeted account (the original Admin/Root) has its access levels wiped or replaced by the attacker\u0027s input, effectively locking the real administrator out of the system.\n\n### PoC\n1. Log in as a Super User (e.g., root0) and create a low-privileged user (e.g., adminuser).\n2. Assign adminuser the following specific permissions:\nadmin.login\nadmin.users.list\nadmin.users.read\nadmin.users.create\n3. Log out and log back in as adminuser.\n4. Navigate to User Accounts -\u003e Add.\n5. Fill in the form with the following details:\nUsername: root0 (The exact username of the Super User)\nEmail: `anything@grav.f`\nFullname: Fake Root0\n7. Click Save.\n8. Observe that the account is successfully \"created\".\n9. The original administrative permissions are gone, and the account is now restricted.\n\n#### PoC video\nhttps://github.com/user-attachments/assets/047cb44e-0279-402b-b4fb-12bf5d427a5e\n\n### Impact\nThis is a Privilege De-escalation and Account Disruption vulnerability.\nWho is impacted: Any Grav installation where a non-admin user is granted permission to create other users.\nConsequence: An attacker can effectively disable all administrative accounts on the platform, leading to a complete loss of management control over the CMS.\n\n\n---\n\n## Maintainer note \u2014 fix applied (2026-04-24)\n\nFixed in Grav core on the `2.0` branch: commit [`d904efc33`](https://github.com/getgrav/grav/commit/d904efc33) \u2014 will ship in **2.0.0-beta.2**.\n\n**What changed:** `UserObject::save` already had a uniqueness guard (commit [`19c2f8da7`](https://github.com/getgrav/grav/commit/19c2f8da7), November 2025) that blocks the PoC. This release tightens that guard:\n\n1. `strpos($key, \u0027@@\u0027)` \u2192 `str_contains($key, \u0027@@\u0027)`. The previous form was falsy when the transient-key marker was at position 0 (e.g. `@@hash`), silently bypassing the check. `str_contains` returns a proper boolean.\n2. The `instanceof FileStorage` gate was dropped so the uniqueness check runs for any `FlexStorageInterface` backend \u2014 not just the default file-per-user YAML one.\n\nA low-privileged user with `admin.users.create` can no longer disrupt a super-admin account by submitting that admin\u0027s username through the \"add user\" form.\n\n**Files:**\n- [`system/src/Grav/Common/Flex/Types/Users/UserObject.php`](https://github.com/getgrav/grav/blob/2.0/system/src/Grav/Common/Flex/Types/Users/UserObject.php).\n- [`tests/unit/Grav/Common/Security/UserOverwriteSecurityTest.php`](https://github.com/getgrav/grav/blob/2.0/tests/unit/Grav/Common/Security/UserOverwriteSecurityTest.php) \u2014 3 tests pinning the PoC, the `@@`-prefix edge case, and pass-through for free usernames.",
  "id": "GHSA-rr73-568v-28f8",
  "modified": "2026-05-13T13:52:30Z",
  "published": "2026-05-05T21:29:53Z",
  "references": [
    {
      "type": "WEB",
      "url": "https://github.com/getgrav/grav/security/advisories/GHSA-rr73-568v-28f8"
    },
    {
      "type": "ADVISORY",
      "url": "https://nvd.nist.gov/vuln/detail/CVE-2026-42609"
    },
    {
      "type": "WEB",
      "url": "https://github.com/getgrav/grav/commit/5a12f9be8314682c8713e569e330f11805d0a663"
    },
    {
      "type": "WEB",
      "url": "https://github.com/getgrav/grav/commit/c66dfeb5ff679a1667678c6335eb9ff3255dfc47"
    },
    {
      "type": "WEB",
      "url": "https://github.com/getgrav/grav/commit/d904efc33e03ebb597afde8d3368b28cf0423632"
    },
    {
      "type": "PACKAGE",
      "url": "https://github.com/getgrav/grav"
    }
  ],
  "schema_version": "1.4.0",
  "severity": [
    {
      "score": "CVSS:3.1/AV:N/AC:L/PR:L/UI:N/S:U/C:N/I:H/A:H",
      "type": "CVSS_V3"
    }
  ],
  "summary": "Grav Vulnerable to Administrative Account Disruption and Privilege De-escalation via User Overwrite Logic"
}

Sightings

Author	Source	Type	Date	Other

Nomenclature

Seen: The vulnerability was mentioned, discussed, or observed by the user.
Confirmed: The vulnerability has been validated from an analyst's perspective.
Published Proof of Concept: A public proof of concept is available for this vulnerability.
Exploited: The vulnerability was observed as exploited by the user who reported the sighting.
Patched: The vulnerability was observed as successfully patched by the user who reported the sighting.
Not exploited: The vulnerability was not observed as exploited by the user who reported the sighting.
Not confirmed: The user expressed doubt about the validity of the vulnerability.
Not patched: The vulnerability was not observed as successfully patched by the user who reported the sighting.

Detection rules are retrieved from Rulezet.

Action not permitted

CVE-2026-42609 (GCVE-0-2026-42609)

FKIE_CVE-2026-42609

GHSA-RR73-568V-28F8

Summary

Details

PoC

PoC video

Impact

Maintainer note — fix applied (2026-04-24)

Tags

Sightings

Nomenclature