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CVE-2021-21425

Unauthenticated Arbitrary YAML Write/Update leads to Code Execution

9.3 CriticalPublic exploit

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.

Attack profile

How easy it is to exploit

Attack vector
Network
Complexity
Low
Privileges needed
None
User interaction
None

What an attacker can affect

Confidentiality
Low
Integrity
High
Availability
None

Exploit likelihood

80.6%Up 79.4 points since Apr 14, 2021
90%50%10%1%

What each source reports

CVE List Score used 9.3

Unauthenticated Arbitrary YAML Write/Update leads to Code Execution

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.

Record
CVE-2021-21425
CVSS 3.1
9.3 CriticalCVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:C/C:L/I:H/A:N
Weakness
CWE-284
Updated
2026-11-02
EUVDEUVD-2021-8706 9.3

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.

Record
EUVD-2021-8706
CVSS 3.1
9.3 CriticalCVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:C/C:L/I:H/A:N
Updated
2026-11-03
NVD 9.3

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.

Record
CVE-2021-21425
CVSS 3.1
9.3 CriticalCVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:C/C:L/I:H/A:N
CVSS 3.1
9.8 CriticalCVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:H/I:H/A:H
CVSS 2.0
7.5 HighAV:N/AC:L/Au:N/C:P/I:P/A:P
Weakness
CWE-284
Updated
2026-11-02
OSV 9.8

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.

Record
CVE-2021-21425
CVSS 3.1
9.8 CriticalCVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:H/I:H/A:H
Updated
2026-11-02

Affected products

Public exploits

Links only. Every CVE stores no exploit code.

Public exploits
SourceLinkDate
Exploit-DBGravCMS 1.10.7 - Unauthenticated Arbitrary File Write (Metasploit)2021-04-21
MetasploitGravCMS Remote Command Execution2021-03-29
PoC in GitHubCsEnox/CVE-2021-214252021-06-24
PoC in GitHubafifudinmtop/CVE-2021-214252026-01-21
PoC in GitHubbluetoothStrawberry/cve-2021-214252024-11-13
PoC in GitHubd4ytox/CVE-2021-214252026-06-13
PoC in GitHubgrey-master-a/GravCMS_Nmap_Script2022-01-19
PoC in GitHubs1lentf00thold/CVE-2021-21425-RCE2026-06-23

History

History
RecordedChangedSources
aliasesEUVD
first indexedCVE List, Exploit-DB, Metasploit, NVD, OSV, PoC in GitHub

Dates are when Every CVE recorded each change. Upstream dates may differ.

In short

CVE-2021-21425 is a critical vulnerability (CVSS 9.3) in Getgrav Grav-plugin-admin, published April 7, 2021. Public exploit code exists. EPSS puts the chance of exploitation in the next 30 days at 80.6%, the 99th percentile. No source names a fixed version.

References

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