MacOS Vulnerability: Use After Free

By Joshua Bourns on May 3, 2024

Executive Summary

On March 28, 2024, CVE-2023-42950, a critical vulnerability in macOS that affects Safari and potentially other WebKit-based browsers was rediscovered. This vulnerability allows attackers to execute arbitrary code through maliciously crafted web content, granting them control over the affected system. It emphasizes the importance of applying security updates promptly to maintain a secure macOS environment. The report also explores similar macOS vulnerabilities to provide context for the ongoing need for vigilance.

Background

CVE-2023-42950 is a “use after free” vulnerability within WebKit, the rendering engine used by Safari and other macOS browsers. “Use after free” vulnerabilities occur when code attempts to access memory that has already been freed, leading to unpredictable program behavior and potential exploitation (MITRE). This specific vulnerability can be triggered by a user visiting a compromised website or opening a malicious attachment.

Similar macOS Vulnerabilities

The prevalence of macOS vulnerabilities is a continuous concern. CVE-2022-42879, a critical vulnerability patched in macOS Monterey 12.5.1, exemplified this risk. It allowed attackers to bypass security restrictions and gain complete control of a system (Apple, 2022). This highlights the potential severity of these vulnerabilities. Another example is CVE-2021-30869, addressed in macOS Big Sur 11.6. Shlayer malware exploited this vulnerability to bypass security measures and install malicious applications (Avira, 2021). These instances demonstrate that attackers are constantly seeking ways to exploit weaknesses in macOS, making vigilance and strong security practices essential.

Technical Details and Impact

While the specifics of CVE-2023-42950 are not publicly disclosed to thwart attackers (NIST, 2023), it is known to be a memory management issue exploitable through malicious web content. This means attackers could potentially craft websites or web content that tricks a user’s browser into triggering the vulnerability. A successful exploit could have a significant impact. Attackers might gain unauthorized access to a system and steal user data. They could also install malware or other malicious software, potentially disrupting system functionality or launching further attacks within the network.

Mitigation

Fortunately, there are steps you can take to mitigate the risks posed by CVE-2023-42950. The most critical action is to install the security update that addresses this vulnerability. Apple has released updates for macOS Monterey 14.2 and macOS Ventura 13.2 that fix this issue (Apple, 2023). In addition to software updates, users should practice caution while browsing the web. Be wary of suspicious websites and avoid downloading untrusted files. Finally, using a robust security solution alongside a firewall can provide additional protection against various threats, including those exploiting this vulnerability.

Conclusion

The prevalence of vulnerabilities like CVE-2023-42950 underscores the importance of software updates and user awareness. Keeping macOS updated with the latest security patches is crucial to maintain a secure system. Additionally, practicing safe browsing habits and being cautious of online interactions helps minimize the risk of exploitation.

References

[1] Apple, “About the security content of macOS Monterey 12.5.1.,” Jul. 12, 2022 https://support.apple.com/en-us/103006

[2] Apple, “About the security content of macOS Ventura 13.2 and macOS Monterey 14.2.,” Dec. 13, 2022 https://support.apple.com/en-us/HT214036

[3] Avira, “Shlayer Malware Uses New macOS Vulnerability (CVE-2021-30869) to Bypass Gatekeeper,” Aug. 19, 2021 https://support.avira.com/hc/en-us/articles/360014089817-Does-Avira-Security-for-Mac-run-on-older-operating-systems

[4] MITRE Corporation, “CWE-416: Use After Free,” (n.d.) https://www.cvedetails.com/cwe-details/416/Use-After-Free.html

[5] National Institute of Standards and Technology, “CVE-2023-42950 Detail. National Vulnerability Database,” Nov. 18, 2023 https://nvd.nist.gov/vuln/detail/CVE-2023-42950