cbcvebase.
CVE-2021-30657
published 2021-09-08

CVE-2021-30657: A logic issue was addressed with improved state management. This issue is fixed in macOS Big Sur 11.3, Security Update 2021-002 Catalina. A malicious…

PriorityP181medium5.5CVSS 3.1
AVLACLPRNUIRSUCNIHAN
KEVITWEXPLOIT
CISA Known Exploited Vulnerabilitydue 2021-11-17
Exploited in the wild
EPSS
68.53%
99.3th percentile
A logic issue was addressed with improved state management. This issue is fixed in macOS Big Sur 11.3, Security Update 2021-002 Catalina. A malicious application may bypass Gatekeeper checks. Apple is aware of a report that this issue may have been actively exploited..

Affected

8 ranges
VendorProductVersion rangeFixed in
applemac_os_x
applemac_os_x
applemac_os_x10.15 – 10.15.5
applemacos>= 11.0 < 11.311.3
applemacos>= unspecified < 11.311.3
applemacos>= unspecified < 20212021
applemacos_big_sur
applesecurity_update_2021-002_catalina

Detection & IOCsextracted from sources · hover to see the quote

urlhttps://github.com/rapid7/metasploit-framework/blob/master/modules/exploits/osx/browser/osx_gatekeeper_bypass.rb
  • Detect macOS .app bundles delivered as ZIP archives that are missing an Info.plist file — this is the core bypass mechanism for CVE-2021-30657 on macOS < 11.3.
  • Monitor Safari's automatic ZIP extraction behaviour: if a ZIP containing a .app bundle (without Info.plist) is downloaded via Safari, it is auto-extracted and can be launched without a Gatekeeper prompt — alert on .app execution immediately following a Safari download event.
  • Alert on .app bundles launched from the Downloads directory that lack a com.apple.quarantine extended attribute AND have no Info.plist — both conditions together indicate a likely Gatekeeper bypass attempt.
  • The vulnerable component is System Preferences on macOS; monitor for unexpected process spawning from System Preferences or Gatekeeper-related processes (syspolicyd) on macOS versions below Big Sur 11.3 / Security Update 2021-002 Catalina.
  • ·The bypass only affects macOS versions below Big Sur 11.3 and unpatched Catalina (pre Security Update 2021-002). Systems running 11.3+ or with the Catalina security update applied are not vulnerable.
  • ·Apple confirmed active in-the-wild exploitation of this vulnerability at time of disclosure; treat any unpatched macOS endpoint as actively at risk.
  • ·The Metasploit module covers two CVEs (CVE-2021-30657 and CVE-2022-22616); ensure detections are scoped correctly — the no-Info.plist ZIP delivery technique maps specifically to CVE-2021-30657.

CVSS provenance

nvdv3.15.5MEDIUMCVSS:3.1/AV:L/AC:L/PR:N/UI:R/S:U/C:N/I:H/A:N
nvdv2.04.3MEDIUMAV:N/AC:M/Au:N/C:N/I:P/A:N
vulncheck5.5MEDIUM
cisa5.5MEDIUM
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