Advisory Details

December 8th, 2020

Apple macOS CoreText MorxLigatureSubtableBuilder TTF Parsing Out-of-Bounds Write Remote Code Execution Vulnerability

ZDI-20-1406
ZDI-CAN-11828

CVE ID CVE-2020-9999
CVSS SCORE 7.8, AV:L/AC:L/PR:N/UI:R/S:U/C:H/I:H/A:H
AFFECTED VENDORS Apple
AFFECTED PRODUCTS macOS
VULNERABILITY DETAILS

This vulnerability allows remote attackers to execute arbitrary code on affected installations of Apple macOS. Interaction with the CoreText library is required to exploit this vulnerability but attack vectors may vary depending on the implementation.

The specific flaw exists within the parsing of TTF fonts. Crafted data in a TTF file can trigger a write past the end of an allocated data structure. An attacker can leverage this vulnerability to execute code in the context of the current process.

ADDITIONAL DETAILS

This issue was addressed in macOS Big Sur 11.0.1.


DISCLOSURE TIMELINE
  • 2020-08-26 - Vulnerability reported to vendor
  • 2020-12-08 - Coordinated public release of advisory
CREDIT Mickey Jin & Junzhi Lu of Trend Micro Mobile Security Research Team
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