CVE-2026-84558 Overview
CVE-2026-84558 is a double free vulnerability [CWE-415] in Apple macOS that can be triggered by a local application. Successful exploitation causes unexpected system termination, resulting in a denial-of-service condition on the affected host. Apple addressed the flaw through improved memory management in macOS Golden Gate 27.
The issue requires local access and low privileges but no user interaction. It affects availability only, with no impact to confidentiality or integrity. The vulnerability is tracked with an EPSS score indicating a low probability of exploitation in the near term, and it is not listed in the CISA Known Exploited Vulnerabilities catalog.
Critical Impact
A local application can trigger a double free condition in macOS memory management routines, causing the operating system to terminate unexpectedly and disrupt user workloads.
Affected Products
- Apple macOS versions prior to Golden Gate 27
- Systems running unpatched macOS builds referenced in Apple advisory HT149035
- All hardware platforms supported by the affected macOS releases
Discovery Timeline
- 2026-09-14 - CVE-2026-84558 published to NVD
- 2026-09-17 - Last updated in NVD database
Technical Details for CVE-2026-84558
Vulnerability Analysis
The vulnerability is a double free condition in a macOS component. A double free occurs when the same memory allocation is released twice through calls such as free() on an already-freed pointer. This corrupts the heap allocator's internal bookkeeping structures.
An application with local access can invoke the affected code path to trigger the second free operation. The resulting heap corruption destabilizes kernel or system-level memory management, leading to an unexpected system termination. Apple's advisory notes the fix uses improved memory management, which typically means clearing stale pointers or adding reference tracking to prevent the second release.
The scope is limited to availability. The CVE description does not indicate that the flaw allows code execution or information disclosure. However, double free vulnerabilities on macOS have historically been used as building blocks in more complex exploit chains when combined with heap grooming techniques.
Root Cause
The root cause is improper tracking of memory ownership in an affected macOS component. A pointer is freed on one code path and subsequently freed again without being nullified or re-validated. This aligns with the CWE-415 weakness class covering duplicate release of the same resource.
Attack Vector
Exploitation requires a local, authenticated context. An attacker delivers or executes an application on the target macOS system that issues the specific sequence of system calls or IPC messages that reach the vulnerable free path. No user interaction is required beyond running the malicious app. Remote exploitation over the network is not possible.
Apple has not published exploitation code, and no public proof-of-concept is available in the referenced sources. Refer to the Apple Support Article for the component-level details Apple has disclosed.
Detection Methods for CVE-2026-84558
Indicators of Compromise
- Repeated unexpected kernel panics or system restarts on macOS endpoints running builds older than Golden Gate 27
- Panic logs in /Library/Logs/DiagnosticReports/ referencing heap corruption, free(), or zone allocator faults
- Execution of unsigned or newly-installed applications immediately preceding system termination events
Detection Strategies
- Monitor macOS diagnostic reports and kernel.log for panic strings such as double free, zfree, or zone_require failures
- Correlate process launch telemetry with abrupt endpoint reboot events across the fleet
- Track installation of unsigned binaries or applications originating from outside the Mac App Store on unpatched hosts
Monitoring Recommendations
- Enroll macOS endpoints in centralized logging to forward DiagnosticReports and unified log data to a SIEM
- Establish a baseline for kernel panic frequency per host and alert on statistically significant deviations
- Maintain an inventory of macOS build numbers to identify systems still exposed to CVE-2026-84558
How to Mitigate CVE-2026-84558
Immediate Actions Required
- Upgrade all macOS endpoints to macOS Golden Gate 27 or later as directed in the Apple Support Article
- Restrict installation of untrusted third-party applications on systems that cannot be immediately patched
- Enable Gatekeeper and require notarized applications to reduce the risk of malicious local code execution
Patch Information
Apple released the fix in macOS Golden Gate 27 with improved memory management in the affected component. Administrators should validate the installed build using sw_vers and deploy the update through Software Update, MDM, or Apple Business Manager. Full patch details are available in the Apple Support Article.
Workarounds
- Limit local user privileges and remove administrator rights from standard user accounts where feasible
- Use MDM configuration profiles to restrict application execution to allowlisted developer identifiers
- Isolate high-value macOS systems from workloads that execute untrusted code until the patch is deployed
Disclaimer: This content was generated using AI. While we strive for accuracy, please verify critical information with official sources.