CVE-2017-20201: Piriform CCleaner

CCleaner v5.33.6162 & CCleaner Cloud v1.07.3191 Malicious Backdoor Supply Chain Compromise

CVSS 9.3 CriticalCriticalEPSS 0.0053 · 44th percentile

Critical, because:

CVSS score 9.3: 9.0 or more.

Published by the CVE Program (CNA: VulnCheck) at 8 Oct 2025, 22:04 UTC. agentprime has not analysed this yet, so whether it affects any app is not known. This CVE names a vendor and product rather than a package, so the lockfile check doesn’t match it.

Affected products, as the CNA wrote them
Vendor	Product	Versions
Piriform	CCleaner	affected 5.33.6162 Other versions: unaffected
Piriform	CCleaner Cloud	affected 1.07.3191 Other versions: unaffected

Identifiers

CVE-2017-20201

CNA

VulnCheck

Weakness (CWE)

CWE-506

Not analysed yet

We haven’t published our own analysis of this CVE. If a person reviews it, this page will say what’s affected and what has to be true for it to matter.

Severity and exploitation

Score	Rating	CVSS	Vector	Source
9.3	Critical	4.0	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	CNA (VulnCheck)

CISA KEV Not listed.
EPSS 0.0053, the 44th percentile, on 5 Nov 2026: FIRST’s estimate of the chance of exploitation in the next 30 days.

Timeline

This record came from the full history of the CVE Program, published 8 Oct 2025. New records show when each source confirmed them.

Sources

References from the CNA

blog.avast.com/update-to-the-ccleaner-5.33.6162-security-incident vendor-advisory
blog.avast.com/progress-on-ccleaner-investigation vendor-advisory
www.ccleaner.com/ product
www.crowdstrike.com/en-us/blog/protecting-software-supply-chain-deep-insights-ccleaner-backdoor/ technical-description
www.ccleaner.com/knowledge/security-notification-ccleaner-v5336162-ccleaner-cloud-v1073191 vendor-advisorypatch
www.morphisec.com/blog/morphisec-discovers-ccleaner-backdoor/ technical-description
blog.talosintelligence.com/avast-distributes-malware/ technical-description
www.vulncheck.com/advisories/ccleaner-and-ccleaner-cloud-malicious-backdoor-supply-chain-compromise third-party-advisory

Facts on this page come from the CVE List as the CNA published them, with CVSS from the sources named above, CISA KEV and FIRST EPSS. Vendors, products and versions are shown as the CNA wrote them. We don’t reproduce the CVE’s description.