Vulnerability · CVE-2020-9771
macOS APFS Snapshot Mount Authorization Bypass
Published Aug 13, 2026 · corrected/updated Aug 13, 2026 · Apple MacOS X · evidence confidence very high
This issue was addressed with a new entitlement. This issue is fixed in macOS Catalina 10.15.4. A user may gain access to protected parts of the file system.
Grounded briefings
Catalog interpretations for three audiences. Each brief cites ingested metadata and the original advisories below. They are not independent research and they do not invent exploit steps.
Executive
CVE-2020-9771 is a unknown public vulnerability record for Apple MacOS X. CISA lists it as known exploited. Published remediation guidance: Apply remediations or mitigations per vendor instructions or discontinue use of the product if remediation or mitigations are unavailable. This summary is a catalog interpretation of the ingested metadata and cites the original advisories below.
System administrator
Identify whether Apple MacOS X is in your estate, then compare installed versions with the affected ranges. Affected packages or ranges on record: Apple MacOS X. Published remediation guidance: Apply remediations or mitigations per vendor instructions or discontinue use of the product if remediation or mitigations are unavailable. Prefer the vendor or distribution advisory linked in Sources before changing production systems. This is a catalog interpretation, not a runbook.
Security analyst
Signals on file: EPSS 0.4%. CISA lists it as known exploited. Sources contributing to this record: epss, vulncheck_kev. Public exploit references, when present, are outbound links only and are not proof of active exploitation. This is a catalog interpretation of stored metadata.
Exploitation and remediation
Exploitation evidence
Confirmed in CISA KEV since Aug 13, 2026. Listed in CISA KEV and VulnCheck KEV.
Patch and remediation
Apply remediations or mitigations per vendor instructions or discontinue use of the product if remediation or mitigations are unavailable.
Safe detection guidance
Compare installed versions with the affected ranges below and verify the advisory from the original publisher. This site stores metadata and outbound links only; it does not ship exploit code or proof-of-concept payloads.
Code
The project this record applies to. Exploit listings stay in References.
No public source repository is identified for this product.
Timeline
Detection, updates, and resolution for this record.
Aug 13, 2026 · VulnCheck KEV
Detected
This issue was addressed with a new entitlement. This issue is fixed in macOS Catalina 10.15.4. A user may gain access to protected parts of the file system.
Aug 13, 2026 · CISA KEV
Known exploited
Apply remediations or mitigations per vendor instructions or discontinue use of the product if remediation or mitigations are unavailable.
Affected
- vendor Apple MacOS Xversion unspecified
Sources
- FIRST EPSSExploitation probabilityCVE-2020-9771
30-day exploitation probability 0.4%
first.org - VulnCheck KEVConfirmed exploitationCVE-2020-9771
This issue was addressed with a new entitlement. This issue is fixed in macOS Catalina 10.15.4. A user may gain access to protected parts of the file system.
vulncheck.com