CVE-2019-8526
Apple macOS Use-After-Free Vulnerability
Description
CVE-2019-8526 is a high-severity use-after-free vulnerability in Apple macOS that allows a local application to gain elevated privileges. The flaw was addressed with improved memory management in macOS Mojave 10.14.4. By exploiting this use-after-free condition, an attacker with local access and low-level privileges can escalate to higher system privileges, potentially gaining full control of the affected Mac. With a CVSS score of 7.8 and confirmed active exploitation in the wild, CISA has added CVE-2019-8526 to its Known Exploited Vulnerabilities catalog, making it a priority for organizations running unpatched macOS systems.
KEV Information
CVSS Score
CVSS:3.1/AV:L/AC:L/PR:L/UI:N/S:U/C:H/I:H/A:HOpen in CalculatorAffected Products
| Vendor | Product | Version |
|---|---|---|
| apple | mac os x | < 10.14.4 |
Multiple CVSS Assessments
CVSS:3.1/AV:L/AC:L/PR:L/UI:N/S:U/C:H/I:H/A:H
CVSS:3.1/AV:L/AC:L/PR:L/UI:N/S:U/C:H/I:H/A:H
References
- https://support.apple.com/HT209600(Release Notes, Vendor Advisory)
- https://www.cisa.gov/known-exploited-vulnerabilities-catalog?field_cve=CVE-2019-8526(US Government Resource)
Weakness Type
CWE-416: Use After Free
The use-after-free weakness in CVE-2019-8526 occurs in macOS when the system references a memory location after it has been freed. In this specific case, the application continues to use a pointer to memory that has already been deallocated, allowing an attacker to manipulate the contents of that memory region. By controlling what data is placed in the freed memory, a local attacker can redirect program execution to achieve privilege escalation on the affected macOS system.
Learn more: CWE-416 — Use After Free
Impact Analysis
CVE-2019-8526 carries a CVSS 3.1 score of 7.8 (High), indicating significant risk for unpatched macOS systems. Unlike network-based attacks, this vulnerability requires local access to the target machine, meaning the attacker must already have the ability to execute code on the system or have physical access. The attack complexity is low, requiring no special conditions or race conditions to trigger. Low-level privileges are required, meaning a standard user account is sufficient to launch the exploit, but no user interaction is needed beyond the attacker running their malicious application. Confidentiality, integrity, and availability impacts are all rated high, as a successful privilege escalation can grant the attacker root-level access, enabling them to read all user data, modify system configurations, and install persistent malware. The EPSS score of 0.54% (67th percentile) indicates moderate exploitation likelihood in the broader landscape, though CISA's inclusion in the KEV catalog confirms that this vulnerability has been actively exploited by threat actors.
Exploit Maturity
CISA has confirmed active exploitation of CVE-2019-8526 in the wild and added it to the Known Exploited Vulnerabilities catalog with a remediation deadline of May 8, 2023. While no widely circulated public exploit code has been identified on major exploit databases, the confirmed in-the-wild exploitation demonstrates that threat actors have developed working exploits. The EPSS score of 0.54% (67th percentile) suggests moderate exploitation probability, but the local privilege escalation capability makes this vulnerability valuable for post-compromise attack chains. Ransomware association is currently unknown for this vulnerability.
Remediation
- Update macOS to version 10.14.4 (Mojave) or later as directed by CISA: apply mitigations per vendor instructions or discontinue use of the product if mitigations are unavailable. Apple's security update addressing this vulnerability is documented in the Apple support article HT209600.
- Upgrade to a currently supported macOS version if running macOS Mojave or earlier. Apple no longer provides security updates for older macOS releases, so systems should be migrated to a supported version to receive ongoing security patches.
- Implement endpoint protection with application whitelisting and behavior-based detection to identify and block exploitation attempts. Configure endpoint detection and response (EDR) tools to alert on privilege escalation patterns, including unexpected process privilege changes and use-after-free exploitation indicators.
- Review local user account privileges and enforce the principle of least privilege across all macOS systems. Limit the number of accounts with administrative access and ensure standard users cannot install or execute unauthorized applications that could exploit this vulnerability.
- Monitor system logs for indicators of compromise, including unexpected privilege escalation events, anomalous process behavior, and signs of post-exploitation activity such as unauthorized system modifications or persistence mechanisms. Pay attention to crash reports that may indicate use-after-free exploitation attempts.
Technical Details
CVE-2019-8526 is a use-after-free vulnerability (CWE-416) in Apple macOS, where the system improperly manages memory by continuing to reference a memory location after it has been freed and returned to the allocator. The attack vector is local (AV:L), requiring the attacker to execute code on the target system, with low complexity (AC:L) and low privileges required (PR:L), meaning a standard user account is sufficient. No user interaction (UI:N) is needed beyond running the malicious application. The use-after-free condition allows an attacker to manipulate the contents of the freed memory region through heap spray or other memory manipulation techniques, potentially overwriting function pointers or object vtables to redirect execution flow. By gaining control of the freed memory, the attacker can escalate from a low-privileged user to elevated system privileges, effectively bypassing macOS security boundaries. Apple addressed this vulnerability with improved memory management in macOS Mojave 10.14.4, ensuring proper tracking of memory allocation and deallocation to prevent dangling pointer references.
Frequently Asked Questions
Is CVE-2019-8526 being actively exploited?
Yes, CVE-2019-8526 has been confirmed as actively exploited in the wild by CISA, which added it to the Known Exploited Vulnerabilities catalog with a remediation deadline of May 8, 2023. While ransomware association is currently unknown, the privilege escalation capability makes it valuable for post-compromise attack chains.
What products are affected by CVE-2019-8526?
CVE-2019-8526 affects Apple macOS (Mac OS X) versions prior to macOS Mojave 10.14.4. Any Mac system running an older version of macOS Mojave or earlier operating system versions that have not received this security update is potentially vulnerable.
How do I fix CVE-2019-8526?
Update to macOS Mojave 10.14.4 or later as documented in Apple support article HT209600. If the system is running an end-of-life macOS version, upgrade to a currently supported macOS release. As interim protection, implement endpoint security tools and enforce least-privilege access policies.
How severe is CVE-2019-8526?
CVE-2019-8526 is rated High with a CVSS 3.1 score of 7.8 out of 10. While local access is required, the attack complexity is low and only standard user privileges are needed. A successful exploit can lead to full privilege escalation with high impact on confidentiality, integrity, and availability.
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