CVE-2017-20201
CCleaner v5.33.6162 & CCleaner Cloud v1.07.3191 Malicious Backdoor Supply Chain Compromise
No known exploitation. EPSS puts it in the 42nd percentile. No fix published yet.
What to do
No fixed build or workaround is published yet. Limit exposure and watch for a patch.
What it is
From the CVE record
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.
In plain language
No plain-language summary for this CVE yet.
Exploitation
Where each signal puts this CVE on the scale from published to confirmed exploited.
- CISA KEV
Not in the catalog. CISA has not confirmed exploitation.
- Public exploits
No public exploit or proof of concept found in the sources we track.
- EPSS
0.5% chance of exploitation activity in the next 30 days, which ranks it in the 42nd percentile of scored CVEs.
Exploit Prediction Scoring System, FIRST.org. A probability, not a confirmation.
Lifecycle
4 events over 260 days, from the signal feeds we watch.
- OpenVAS check added
- Record updated
- Publishedweakness classified
Affected products
Technical detail
Weaknesses
Sources
References in the record
- blog.avast.com/progress-on-ccleaner-investigation
- blog.avast.com/update-to-the-ccleaner-5.33.6162-security-incident
- blog.talosintelligence.com/avast-distributes-malware/
And 5 more references. See all after sign-in
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