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CVE-2017-20201: Potential impacts include remote data collection and exfiltration, stealthy in-memory execution and…

CVE-2017-20201 is rated critical with a CVSS v4.0 base score of 9.3. Per its scoring, it can be exploited over the network, without authentication.

Vulnerability 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.

Severity breakdown

CVSS v4.0 9.3: CVSS:4.0/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

  • Attack vector: Network. Exploitable remotely over the network.
  • Attack complexity: Low. No special conditions; the attack can be repeated reliably.
  • Attack requirements: None. No deployment or execution conditions are needed.
  • Privileges required: None. No account or prior access is needed.
  • User interaction: Active. A user must knowingly take specific action.
  • Confidentiality impact (vulnerable system): High. Total loss of confidentiality.
  • Integrity impact (vulnerable system): High. Total loss of integrity.
  • Availability impact (vulnerable system): None. No effect on availability.
  • Confidentiality impact (subsequent systems): High. Total loss of confidentiality on other systems.
  • Integrity impact (subsequent systems): High. Total loss of integrity on other systems.
  • Availability impact (subsequent systems): None. No availability impact beyond the vulnerable system.

Underlying weakness

CWE-506: Embedded Malicious Code

The product contains code that appears to be malicious in nature.

Affected products

    References