CVE-2017-20201
CCleaner v5.33.6162 & CCleaner Cloud v1.07.3191 Malicious Backdoor Supply Chain Compromise
Description
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.
INFO
Published Date :
Oct. 8, 2025, 10:15 p.m.
Last Modified :
Oct. 14, 2025, 3:16 p.m.
Remotely Exploit :
Yes !
Source :
[email protected]
CVSS Scores
| Score | Version | Severity | Vector | Exploitability Score | Impact Score | Source |
|---|---|---|---|---|---|---|
| CVSS 4.0 | CRITICAL | 83251b91-4cc7-4094-a5c7-464a1b83ea10 | ||||
| CVSS 4.0 | CRITICAL | [email protected] |
Solution
- Update CCleaner to version 5.34 or later.
- Update CCleaner Cloud to version 1.07.3214 or later.
- Remove any suspicious or unauthorized software.
- Scan for and remove malware.
References to Advisories, Solutions, and Tools
Here, you will find a curated list of external links that provide in-depth
information, practical solutions, and valuable tools related to
CVE-2017-20201.
CWE - Common Weakness Enumeration
While CVE identifies
specific instances of vulnerabilities, CWE categorizes the common flaws or
weaknesses that can lead to vulnerabilities. CVE-2017-20201 is
associated with the following CWEs:
Common Attack Pattern Enumeration and Classification (CAPEC)
Common Attack Pattern Enumeration and Classification
(CAPEC)
stores attack patterns, which are descriptions of the common attributes and
approaches employed by adversaries to exploit the CVE-2017-20201
weaknesses.
We scan GitHub repositories to detect new proof-of-concept exploits. Following list is a collection of public exploits and proof-of-concepts, which have been published on GitHub (sorted by the most recently updated).
Results are limited to the first 15 repositories due to potential performance issues.
The following list is the news that have been mention
CVE-2017-20201 vulnerability anywhere in the article.
The following table lists the changes that have been made to the
CVE-2017-20201 vulnerability over time.
Vulnerability history details can be useful for understanding the evolution of a vulnerability, and for identifying the most recent changes that may impact the vulnerability's severity, exploitability, or other characteristics.
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CVE Modified by 134c704f-9b21-4f2e-91b3-4a467353bcc0
Oct. 14, 2025
Action Type Old Value New Value Added Reference https://www.crowdstrike.com/en-us/blog/protecting-software-supply-chain-deep-insights-ccleaner-backdoor/ -
New CVE Received by [email protected]
Oct. 08, 2025
Action Type Old Value New Value Added Description 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. Added CVSS V4.0 AV:N/AC:L/AT:N/PR:N/UI:A/VC:H/VI:H/VA:N/SC:H/SI:H/SA:N/E:X/CR:X/IR:X/AR:X/MAV:X/MAC:X/MAT:X/MPR:X/MUI:X/MVC:X/MVI:X/MVA:X/MSC:X/MSI:X/MSA:X/S:X/AU:X/R:X/V:X/RE:X/U:X Added CWE CWE-506 Added Reference https://blog.avast.com/progress-on-ccleaner-investigation Added Reference https://blog.avast.com/update-to-the-ccleaner-5.33.6162-security-incident Added Reference https://blog.talosintelligence.com/avast-distributes-malware/ Added Reference https://www.ccleaner.com/ Added Reference https://www.ccleaner.com/knowledge/security-notification-ccleaner-v5336162-ccleaner-cloud-v1073191 Added Reference https://www.crowdstrike.com/en-us/blog/protecting-software-supply-chain-deep-insights-ccleaner-backdoor/ Added Reference https://www.morphisec.com/blog/morphisec-discovers-ccleaner-backdoor/ Added Reference https://www.vulncheck.com/advisories/ccleaner-and-ccleaner-cloud-malicious-backdoor-supply-chain-compromise