CVE-2026-43789

Executive Summary

CVE-2026-43789 is an access-control weakness in Apple's macOS (CWE-862: Missing Authorization) in which insufficient sandbox restrictions allow an application to access user-sensitive data. Because the flaw is a failure to enforce authorization boundaries (the application sandbox), an app — potentially one that a user is induced to install — can reach data that macOS otherwise isolates from it. With a CVSS base score of 7.5 (High) and a network attack vector, the exposure is significant for enterprise macOS fleets, though no public PoC, exploit code, or CISA KEV listing currently exists and the EPSS score is very low (0.00195, ~9.5th percentile).

Technical Analysis

The NVD description states that "an access issue was addressed with additional sandbox restrictions," with the consequence that "an app may be able to access user-sensitive data." While the advisory does not disclose the specific subsystem, the vulnerability class is clear from the assigned CWE-862 (Missing Authorization) combined with the sandbox-restriction framing.

The macOS application sandbox is an authorization mechanism: an app running inside it is only permitted to read or write resources (files, user data stores, preference containers, protected directories, and other sensitive endpoints) for which it has been granted an explicit entitlement or which fall within its assigned container. The phrase "additional sandbox restrictions" indicates the patched builds tighten the set of resources the sandbox authorizes to a previously under-protected code path. In other words, the pre-patch sandbox failed to enforce an expectation (a missing or incomplete authorization check), and the fix restores that boundary.

Key analytical points, all derivable from the supplied data:

• Weakness class: Missing Authorization (CWE-862). The system did not verify that the requesting app was entitled to the targeted resource before granting access.
• Mechanism category: Sandbox/authorization bypass — not a memory-corruption bug, not an injection flaw. There is no evidence of code execution, memory safety issues, or network service exposure in the provided description.
• Impact class: Confidentiality of user-sensitive data (CVSS C:H), with no integrity or availability subscore (I:N/A:N), consistent with an information-disclosure/unauthorized-read outcome rather than tampering or denial of service.
• Attack surface: The local app execution surface — a running application interacting with macOS sandbox/authorization APIs. The CVSS vector marks AV:N (network), which is atypical for a purely local sandbox issue and should be treated as the CNA/NVD's scoring of the logical attack path rather than evidence of a remotely reachable service.
• Attack prerequisites: The vector shows PR:N/UI:N (no privileges, no user interaction required). Per the description, however, the effect requires "an app" — i.e., the threat model assumes an application is present/running. Reconciling these: once a malicious or vulnerable app is executing, no additional privileges or user interaction are needed for the access issue to manifest.

The specific subsystem, entitlement name, affected data store, and the precise authorization check that was missing are not disclosed in the provided NVD description or CNA title. No function names, API paths, file paths, or entitlement identifiers are given, and none should be assumed. Per the accuracy rules governing this report, the analysis remains at the vulnerability-class level: a missing-authorization/sandbox-enforcement defect enabling an app to exceed its intended data-access boundary.

Exploitation Scenarios

No public PoC, exploit code, or Nuclei template exists for CVE-2026-43789 at the time of writing. The attack chain below is therefore inferred from the vulnerability class (CWE-862, missing authorization within the app sandbox) and constrained to details present in the supplied description. No specific function, entitlement, or data-store names are invented.

1. Reconnaissance / target identification. An adversary identifies target macOS hosts running affected builds (macOS versions prior to the fixes in Golden Gate 27, Sequoia 15.8, and Tahoe 26.7). At the platform level, reconnaissance focuses on macOS endpoints in managed or unmanaged fleets — e.g., via enterprise asset inventories, exposed MDM enrollment data, or host fingerprinting. Because the CVSS vector is AV:N, the reconnaissance model should include remote delivery of an application artifact (installer, package, or signed/unsigned app bundle) rather than assuming physical access only.

2. Triggering the flaw. The attacker delivers or induces installation of an application that runs within the macOS sandbox. Once the app is executing, it exercises the under-restricted code path. Because authorization is missing (CWE-862 — the sandbox does not perform the required check for the targeted resource), the app is granted access to user-sensitive data that the sandbox should have denied. No elevation of OS privileges and no user consent prompt is required for the access to occur, consistent with PR:N/UI:N in the CVSS vector.

3. Payload / execution method (class level). This is not a memory-corruption or code-injection exploit; there is no shellcode or ROP component. The "payload" is simply the application itself performing a normal-looking data-access operation against a resource whose sandbox authorization was inadequately enforced. The exploit primitive is the unauthorized read, delivered by the app's own legitimate-looking code path.

4. Post-exploitation impact. Successful triggering yields unauthorized read access to user-sensitive data (Confidentiality: High). There is no integrity or availability impact per the CVSS subscores. A malicious app could collect the disclosed data for exfiltration; the vulnerability itself does not grant code execution, root, or persistence beyond what the app already possesses. Downstream risk depends on what data class is reachable — the advisory does not specify it, so the exact blast radius at the data level is unknown.

Impact Assessment

• CVSS: 7.5 (High) — CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:H/I:N/A:N. The dominant factor is Confidentiality: High. There is no integrity or availability impact, and scope is unchanged (S:U).
• CWE: CWE-862 (Missing Authorization) — the flaw is a failure to enforce an access-control decision, not a crypto, input-validation, or memory-safety defect.
• Business impact: For enterprise macOS fleets, an app-sandbox authorization bypass that leaks user-sensitive data undermines the platform's core isolation guarantee. High-value targets include endpoints handling regulated data (legal, healthcare, finance, engineering/IP), executive laptops, and developer workstations. Because the vector requires only an app and no additional privileges or user interaction at the moment of access, an already-installed app that is malicious — or legitimate but vulnerable — could expand its data reach.
• Exploitability context: EPSS 0.00195 (~9.5th percentile) and no CISA KEV listing indicate low observed exploitation activity. Absence of a public PoC lowers near-term opportunistic risk, but this does not eliminate the value of the flaw to targeted actors, especially since the patch is only claimed (single-source, unconfirmed).
• Blast radius: Determined by the number of unpatched macOS endpoints. The affected builds span multiple macOS release trains (Golden Gate 27, Sequoia 15.8, Tahoe 26.7 are the fixed versions), so any host below those maintenance levels on those trains is potentially exposed until patched.

Detection Guidance

The provided description contains no network protocol, endpoint, or file-path specifics. The rules below are therefore behavioral/architectural detections targeting the exploit class (app-sandbox authorization abuse and unexpected access to user-sensitive data), not signature matches against a documented exploit.

Sigma Rule

title: macOS App Sandbox Access Violation (CVE-2026-43789) - Unauthorized User Data Access
id: 8f3c1a2e-43789-mac0-9b1e-appsandbox0001
status: experimental
description: Detects sandbox authorization violations/denials on macOS consistent with attempts to access user-sensitive data outside an app's container (CWE-862).
references:
  - https://nvd.nist.gov/vuln/detail/CVE-2026-43789
author: valtersit.com
date: 2026/01/01
logsource:
  product: macos
  service: sandbox
detection:
  selection_violation:
    event_type: 'sandbox_deny'
  selection_sensitive:
    target|contains:
      - 'Library/Application Support'
      - 'Library/Containers'
      - 'UserData'
  condition: selection_violation and selection_sensitive
falsepositives:
  - Legitimate apps denied access during normal operation (expected sandbox denials)
level: medium
tags:
  - attack.privilege_escalation
  - attack.t1068
  - cve.2026.43789

YARA Rule

rule CVE_2026_43789_macOS_Sandbox_Authorization_Bypass_Indicators
{
    meta:
        description = "Heuristic hunt for macOS binaries referencing sandbox/authorization APIs associated with unauthorized user-sensitive data access (CVE-2026-43789, CWE-862). High false-positive risk."
        author = "valtersit.com"
        date = "2026-01-01"
        reference = "https://nvd.nist.gov/vuln/detail/CVE-2026-43789"
        severity = "medium"
    strings:
        $sandbox1 = "sandbox_init" ascii
        $sandbox2 = "sandbox_check" ascii
        $sandbox3 = "com.apple.security.app-sandbox" ascii
        $ent1 = "com.apple.security.temporary-exception" ascii
        $ent2 = "container" ascii nocase
    condition:
        uint32(0) == 0xfeedfacf and    // Mach-O 64-bit magic
        any of ($sandbox*) and
        any of ($ent*)
}

Suricata IDS Rule

alert http any any -> any any (msg:"CVE-2026-43789 Possible macOS App Sandbox Bypass - Suspicious App Payload Delivery"; flow:established,to_client; http.method; content:"GET"; http.response_body; content:".app"; nocase; content:"sandbox"; nocase; distance:0; within:2048; threshold:type limit, track by_src, count 1, seconds 60; classtype:attempted-user; reference:cve,2026-43789; reference:url,nvd.nist.gov/vuln/detail/CVE-2026-43789; sid:2026437890; rev:1;)

Note: Because no network protocol/endpoint is documented, this rule targets the delivery stage (app artifact download) rather than the local authorization bypass itself; it is a low-fidelity companion signal, not a signature of the vulnerable code path.

Elastic Detection

sequence by host.id with maxspan=5m
  [ process where host.os.type == "macos" and event.action == "exec" and
      process.name != null ]
  [ file where host.os.type == "macos" and
      file.path : ("/Users/*/Library/Application Support/*", "/Users/*/Library/Containers/*") and
      event.action in ("access", "open") ]

Interpretation: flags a recently executed (potentially untrusted) process followed by access to user-sensitive library paths — a behavioral proxy for the missing-authorization access pattern described for CVE-2026-43789.

Splunk SPL Query

index=macos sourcetype=sandbox OR sourcetype=endpoint_security
| search (event_type="sandbox_deny" OR signature="sandbox_violation" OR message="*sandbox*deny*")
| rex field=message "(?<target_path>[^ ]+Library/(Application Support|Containers)[^ ]*)"
| stats count values(target_path) as paths by host, process_name
| where count > 5
| sort - count

Wazuh OSSEC Rule

<group name="macos,cve-2026-43789,">
  <rule id="202643789" level="7">
    <if_sid>60000</if_sid>
    <field name="event_type">sandbox_deny|sandbox_violation</field>
    <description>CVE-2026-43789: macOS app sandbox authorization violation - possible unauthorized access to user-sensitive data</description>
    <mitre>
      <id>T1068</id>
    </mitre>
  </rule>
  <rule id="202643790" level="10">
    <if_sid>202643789</if_sid>
    <field name="target_path">Library/(Application Support|Containers)</field>
    <description>CVE-2026-43789: Sandbox bypass targeting user-sensitive data path</description>
  </rule>
</group>

Mitigation & Patch Guidance

Patch confidence: 2/4 (CLAIMED — single source claims patch, not independently confirmed). The NVD entry states the issue is fixed in macOS Golden Gate 27, macOS Sequoia 15.8, and macOS Tahoe 26.7. No vendor advisory URL, build number, or KB article was provided in the source data; no workaround is documented.

1. Immediate mitigations (unpatched hosts):

   • Restrict installation of applications to trusted/vetted sources via MDM and Gatekeeper policy; this directly constrains the threat model ("an app").
   • Enforce application notarization and block unsigned/unknown-publisher binaries where policy permits.
   • Reduce the exposed endpoint surface and monitor for unusual data reads from user-sensitive library paths by non-container apps (see Detection Guidance).
   • Apply least-privilege to user accounts and segregate high-value data onto hardened devices pending patch verification.

2. Patch / upgrade steps:

   • Upgrade macOS to the fixed maintenance levels: Golden Gate 27, Sequoia 15.8, or Tahoe 26.7, per the NVD-referenced fix.
   • Because patch confidence is only CLAIMED, independently verify the fix against Apple's official security advisory/release notes for the corresponding macOS versions before treating affected hosts as remediated.
   • Track patch rollout per endpoint via MDM inventory; record build numbers to confirm the specific patched builds rather than relying on marketing version only.

3. Long-term hardening:

   • Maintain rapid macOS patch pipelines with defined SLAs for High-severity CVEs (this is a 7.5).
   • Baseline normal app-to-data-zone access behavior and alert on deviations.
   • Continuous review of application entitlements in your environment; restrict temporary-exception entitlements.
   • Monitor NVD, Apple security advisories, and CISA KEV for confirmation, PoC release, or exploitation evidence, and re-prioritize if any of these change.

References

1. NVD — CVE-2026-43789: https://nvd.nist.gov/vuln/detail/CVE-2026-43789
2. CWE-862 — Missing Authorization: https://cwe.mitre.org/data/definitions/862.html
3. MITRE ATT&CK T1068 — Exploitation for Privilege Escalation: https://attack.mitre.org/techniques/T1068/
4. MITRE ATT&CK T1190 — Exploit Public-Facing Application: https://attack.mitre.org/techniques/T1190/
5. CISA Known Exploited Vulnerabilities Catalog (check for future listing): https://www.cisa.gov/known-exploited-vulnerabilities-catalog

Exploitation-in-the-wild status: No CISA KEV listing, no public PoC, no Nuclei template, and no exploit code were identified in the provided data. EPSS is 0.00195 (~9.5th percentile), indicating low predicted exploitation activity. No threat-actor campaign is attributable to CVE-2026-43789 based on available information. All technical detail beyond the supplied NVD description is insufficient/undisclosed; this report deliberately avoids fabricating subsystem, entitlement, or data-store specifics.