Piriform CCleaner/CCleaner Cloud Pre-entry-point Loader malicious code

Summaryinfo

A vulnerability was found in Piriform CCleaner and CCleaner Cloud. It has been declared as critical. This affects an unknown function of the component Pre-entry-point Loader. Executing a manipulation can lead to malicious code. This vulnerability is handled as CVE-2017-20201. The attack can be executed remotely. There is not any exploit available. It is recommended to upgrade the affected component.

Detailsinfo

A vulnerability has been found in Piriform CCleaner and CCleaner Cloud (version now known) and classified as critical. This vulnerability affects some unknown processing of the component Pre-entry-point Loader. The manipulation with an unknown input leads to a malicious code vulnerability. The CWE definition for the vulnerability is CWE-506. The product contains code that appears to be malicious in nature. As an impact it is known to affect confidentiality, integrity, and availability. CVE summarizes:

CCleaner v5.33.6162 and CCleaner Cloud v1.07.3191 (32-bit builds) contained a malicious pre-entry-point loader that diverts execution from __scrt_common_main_seh into a custom loader. That loader decodes an embedded blob into shellcode, allocates executable heap memory, resolves Windows API functions at runtime, and transfers execution to an in-memory payload. The payload performs anti-analysis checks, gathers host telemetry, encodes the data with a two-stage obfuscation, and attempts HTTPS exfiltration to hard-coded C2 servers or month-based DGA domains. Potential impacts include remote data collection and exfiltration, stealthy in-memory execution and persistence, and potential lateral movement. CCleaner was developed by Piriform, which was acquired by Avast in July 2017; Avast later merged with NortonLifeLock to form the parent company now known as Gen Digital. According to vendor advisories, the compromised CCleaner build was released on August 15, 2017 and remediated on September 12, 2017 with v5.34; the compromised CCleaner Cloud build was released on August 24, 2017 and remediated on September 15, 2017 with v1.07.3214.

The advisory is shared for download at blog.avast.com. This vulnerability was named CVE-2017-20201 since 10/08/2025. The exploitation appears to be easy. The attack can be initiated remotely. No form of authentication is required for a successful exploitation. Successful exploitation requires user interaction by the victim. There are neither technical details nor an exploit publicly available.

Upgrading eliminates this vulnerability.

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Productinfo

Type

• Cloud Software

Vendor

• Piriform

Name

• CCleaner
• CCleaner Cloud

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