yii-starter-kit yii2-starter-kit up to 4.2.0 Backend Storage Upload unrestricted upload

Summaryinfo

A vulnerability was found in yii-starter-kit yii2-starter-kit up to 4.2.0. It has been classified as critical. The affected element is an unknown function of the component Backend Storage Upload. The manipulation leads to unrestricted upload. This vulnerability is traded as CVE-2026-103474. It is possible to initiate the attack remotely. There is no exploit available.

Detailsinfo

A vulnerability, which was classified as critical, has been found in yii-starter-kit yii2-starter-kit up to 4.2.0. This issue affects an unknown code block of the component Backend Storage Upload. The manipulation with an unknown input leads to a unrestricted upload vulnerability. Using CWE to declare the problem leads to CWE-434. The product allows the attacker to upload or transfer files of dangerous types that can be automatically processed within the product's environment. Impacted is confidentiality, integrity, and availability. The summary by CVE is:

yii2-starter-kit through 4.2.0 fails to validate file types in the backend storage upload actions, allowing authenticated managers to upload PHP files. Attackers with manager role can upload PHP scripts to the web-accessible storage directory and request them to execute arbitrary code on the server.

It is possible to read the advisory at github.com. The identification of this vulnerability is CVE-2026-103474 since 09/30/2026. The exploitation is known to be easy. The attack may be initiated remotely. The technical details are unknown and an exploit is not publicly available. The pricing for an exploit might be around USD $0-$5k at the moment (estimation calculated on 09/30/2026). The attack technique deployed by this issue is T1608.002 according to MITRE ATT&CK.

There is no information about possible countermeasures known. It may be suggested to replace the affected object with an alternative product.

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Productinfo

Vendor

• yii-starter-kit

Name

• yii2-starter-kit

Version

• 4.0
• 4.1
• 4.2.0

Website

• Product: https://github.com/yii-starter-kit/yii2-starter-kit/

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