CVE-2018-4124

Vulnerability

CVE-2018-4124 is a memory corruption vulnerability in the CoreText component of Apple operating systems. It is triggered when the system processes a maliciously crafted string that contains a certain Telugu character. The vulnerability affects iOS versions prior to 11.2.6, macOS High Sierra versions prior to 10.13.3 Supplemental Update, tvOS versions prior to 11.2.6, and watchOS versions prior to 4.2.3 [1][2][3][4]. The issue was addressed by Apple through improved input validation in updates released on February 19, 2018.

Exploitation

To exploit this vulnerability, an attacker must deliver a crafted string containing the specific Telugu character to a target device. This can be accomplished by enticing the user to view a message, open a webpage, or process a document that includes the malicious string. The attacker does not need prior authentication or special privileges, as the vulnerability is triggered during normal string processing by the CoreText framework. Once the string is processed, memory corruption occurs.

Impact

Successful exploitation results in heap corruption, which may lead to a denial of service (application crash or system restart). The official advisory also states that processing a maliciously crafted string may lead to heap corruption, and Apple's description notes that it could allow "unspecified other impact," indicating the possibility of arbitrary code execution at the privilege level of the affected application [1][2][3][4].

Mitigation

Users should update their devices to the patched versions released on February 19, 2018: iOS 11.2.6, macOS High Sierra 10.13.3 Supplemental Update, tvOS 11.2.6, and watchOS 4.2.3 [1][2][3][4]. There are no known workarounds; applying the updates is the only mitigation. This vulnerability is not listed on CISA's Known Exploited Vulnerabilities (KEV) catalog at the time of writing.