CVE-2021-21425

CRITICAL

Grav Admin Plugin < 1.10.8 - Unauthenticated Arbitrary YAML Write via Administrator Controller

Title source: llm
STIX 2.1

Exploitation Summary

EIP tracks 7 public exploits for CVE-2021-21425. PoCs published by Mehmet Ince, CsEnox, bluetoothStrawberry, including Metasploit module exploits/linux/http/gravcms_exec.

AI-analyzed exploit summary This Metasploit module exploits an unauthenticated arbitrary YAML write vulnerability in GravCMS Admin Plugin (CVE-2021-21425) to achieve remote code execution by manipulating the scheduler configuration to execute a PHP payload.

Description

Grav Admin Plugin is an HTML user interface that provides a way to configure Grav and create and modify pages. In versions 1.10.7 and earlier, an unauthenticated user can execute some methods of administrator controller without needing any credentials. Particular method execution will result in arbitrary YAML file creation or content change of existing YAML files on the system. Successfully exploitation of that vulnerability results in configuration changes, such as general site information change, custom scheduler job definition, etc. Due to the nature of the vulnerability, an adversary can change some part of the webpage, or hijack an administrator account, or execute operating system command under the context of the web-server user. This vulnerability is fixed in version 1.10.8. Blocking access to the `/admin` path from untrusted sources can be applied as a workaround.

Exploits (7)

exploitdb WORKING POC VERIFIED
by Mehmet Ince · rubywebappsphp
https://www.exploit-db.com/exploits/49788

This Metasploit module exploits an unauthenticated arbitrary YAML write vulnerability in GravCMS Admin Plugin (CVE-2021-21425) to achieve remote code execution by manipulating the scheduler configuration to execute a PHP payload.

Classification
Working Poc 100%
Attack Type
Rce
Complexity
Moderate
Reliability
Reliable
Target: GravCMS Admin Plugin <= 1.10.7
No auth needed
Prerequisites: Target must have GravCMS Admin Plugin <= 1.10.7 installed · PHP must be available on the target system
devstral-2 · analyzed Feb 16, 2026 Full analysis →
nomisec WORKING POC 11 stars
by CsEnox · poc
https://github.com/CsEnox/CVE-2021-21425

This repository contains a functional exploit for CVE-2021-21425, which targets GravCMS. The exploit leverages unauthenticated arbitrary YAML write/update to achieve remote code execution by scheduling a task to create and execute a shell script.

Classification
Working Poc 95%
Attack Type
Rce
Complexity
Moderate
Reliability
Reliable
Target: GravCMS Admin 1.7.10
No auth needed
Prerequisites: Target URL with vulnerable GravCMS instance
devstral-2 · analyzed Feb 18, 2026 Full analysis →
nomisec WORKING POC 1 stars
by bluetoothStrawberry · poc
https://github.com/bluetoothStrawberry/cve-2021-21425

This repository contains a functional exploit for CVE-2021-21425, targeting GravCMS 1.10.7. The exploit leverages an unauthenticated arbitrary YAML write vulnerability to schedule a malicious cron job, resulting in remote code execution (RCE) via a PHP web shell.

Classification
Working Poc 95%
Attack Type
Rce
Complexity
Moderate
Reliability
Reliable
Target: GravCMS 1.10.7
No auth needed
Prerequisites: Target must be running GravCMS 1.10.7 · Target must have the admin panel accessible · Target must allow writes to the /tmp directory
devstral-2 · analyzed Feb 18, 2026 Full analysis →
nomisec WORKING POC
by d4ytox · poc
https://github.com/d4ytox/CVE-2021-21425

This repository contains a functional exploit for CVE-2021-21425, an unauthenticated RCE vulnerability in GravCMS <= 1.10.7. The exploit abuses the scheduler configuration to create a malicious cron job that executes arbitrary PHP code, resulting in remote command execution.

Classification
Working Poc 100%
Attack Type
Rce
Complexity
Moderate
Reliability
Reliable
Target: GravCMS <= 1.10.7
No auth needed
Prerequisites: Access to the GravCMS admin panel endpoint · Network connectivity to the target
devstral-2 · analyzed Jun 13, 2026 Full analysis →
nomisec WORKING POC
by TeddyEngel · poc
https://github.com/TeddyEngel/CVE-2021-21425

This repository contains a functional exploit for CVE-2021-21425, an unauthenticated RCE vulnerability in GravCMS <= 1.10.7. The exploit abuses the scheduler configuration to create a malicious cron job that executes arbitrary PHP code.

Classification
Working Poc 100%
Attack Type
Rce
Complexity
Moderate
Reliability
Reliable
Target: GravCMS <= 1.10.7
No auth needed
Prerequisites: Access to the GravCMS admin panel endpoint · Python 3 with requests library
devstral-2 · analyzed May 19, 2026 Full analysis →
nomisec WORKING POC
by afifudinmtop · poc
https://github.com/afifudinmtop/CVE-2021-21425

This repository contains a functional exploit for CVE-2021-21425, targeting GravCMS 1.10.7. The exploit leverages an unauthenticated arbitrary YAML write/update vulnerability to achieve remote code execution (RCE) by scheduling a malicious PHP command via the admin tools.

Classification
Working Poc 95%
Attack Type
Rce
Complexity
Moderate
Reliability
Reliable
Target: GravCMS 1.10.7
No auth needed
Prerequisites: Target must be running GravCMS 1.10.7 · Network access to the target's admin interface
devstral-2 · analyzed Feb 19, 2026 Full analysis →
metasploit WORKING POC NORMAL
by Mehmet Ince <[email protected]> · rubypoc
https://github.com/rapid7/metasploit-framework/blob/master/modules/exploits/linux/http/gravcms_exec.rb

This Metasploit module exploits an unauthenticated arbitrary YAML write vulnerability in GravCMS Admin Plugin (CVE-2021-21425) to achieve remote code execution by manipulating the scheduler configuration to execute a PHP payload.

Classification
Working Poc 100%
Attack Type
Rce
Complexity
Moderate
Reliability
Reliable
Target: GravCMS Admin Plugin <= 1.10.7
No auth needed
Prerequisites: Target must have GravCMS Admin Plugin installed and vulnerable · PHP must be available on the target system
devstral-2 · analyzed Feb 16, 2026 Full analysis →

Scores

CVSS v3 9.3
EPSS 0.9164
EPSS Percentile 99.7%
Attack Vector NETWORK
CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:C/C:L/I:H/A:N

Details

CWE
CWE-284
Status published
Products (1)
getgrav/grav-plugin-admin < 1.10.8
Published Apr 07, 2021
Tracked Since Feb 18, 2026