CVE-2026-86903

Executive Summary

CVE-2026-86903 is an out-of-bounds read (CWE-125) in Apple's operating systems that was addressed through improved input validation. Successful exploitation allows a locally installed app to disclose kernel memory, a high-integrity confidentiality boundary crossing within Apple's security model. Patches are claimed for iOS 27, iPadOS 27, macOS Golden Gate 27, tvOS 27, visionOS 27, and watchOS 27. Exploitation requires local code execution with low privileges, and no public proof-of-concept, exploit code, or Nuclei template is known; the EPSS score of 0.00116 and absent CISA KEV listing indicate no observed in-the-wild exploitation at time of writing.

Technical Analysis

CVE-2026-86903 is classified under CWE-125, Out-of-bounds Read. The NVD description states plainly that the issue "was addressed with improved input validation" and that "an app may be able to disclose kernel memory." These two facts define the entire technical scope available from primary data, and the analysis below is deliberately constrained to them rather than speculative internals.

Vulnerability class mechanics: An out-of-bounds read occurs when a code path computes or trusts a length, index, or buffer bound that does not match the actual allocated region, and subsequently reads (or returns) bytes beyond the valid boundary. In kernel contexts, such over-reads are most consequential because adjacent memory frequently contains pointers, credentials, cryptographic key material, or other processes' data. When the over-read is reachable from an unprivileged user-space application—as the description implies via "an app may be able to disclose kernel memory"—the result is an information disclosure primitive operating across the user/kernel trust boundary.

The precise parsing interface, IOUserClient method, syscall, or driver entry point involved is not identified in the CNA title (empty) or NVD description. No function names, symbols, API paths, or parameters are provided in the source data. Accordingly, this report does not attribute the flaw to any specific subsystem (e.g., the XNU kernel proper, a driver, or a system service). What can be stated with confidence is the class of root cause: insufficient validation of input that influences a memory access length or offset, allowing a read past the end of an intended buffer and returning kernel-resident bytes to the calling application.

Attack surface: The attack surface is a local application running within the standard OS security posture. The CVSS vector—AV:L (Local), AC:L (Low), PR:L (Low privileges), UI:N (No user interaction), S:U (Unchanged scope), C:H (High confidentiality), I:N (No integrity), A:N (No availability)—confirms the mechanism. The attacker needs the ability to execute an app on the device (PR:L). No victim interaction is required (UI:N). The scope is unchanged, meaning the vulnerable component's authorization context is not itself escalated by the flaw; the value lies purely in the disclosed data (C:H).

Impact boundary: The High confidentiality subscore and No integrity/availability subscores are consistent with a pure read primitive. This is not a remote code execution or memory-corruption write; it does not by itself grant code execution. Its value is as a building block—kernel address disclosure strengthens ASLR bypass, and kernel data disclosure can expose sensitive material. That said, the exact contents exposed are not specified by the source data and should not be overstated.

Exploitation Scenarios

No public PoC or exploit code exists for CVE-2026-86903. The following chain is described at the vulnerability-class level and is inferred from the CVSS vector and the CWE-125 class; no specific function names, endpoints, or parameters are asserted because none are provided in the source data.

1. Reconnaissance / target identification: A local attacker first needs code execution on a vulnerable build—a malicious or trojanized app, a compromised legitimate app, or a sideloaded/malicious application. The attacker identifies the target OS version is below the patched releases (iOS/iPadOS < 27, macOS Golden Gate < 27, tvOS < 27, visionOS < 27, watchOS < 27). Because AV is Local and PR is Low, the app runs within its normal sandbox/app entitlements; no special privilege is needed.

2. Triggering the flaw class: The attacker's app invokes the vulnerable input-handling interface with crafted input designed to manipulate a length, count, or offset value. The insufficient input validation described by NVD allows the code path to compute a read bound larger than the intended buffer, or to accept an attacker-influenced offset. Where exactly this input enters the kernel is not detailed in the source material; at the class level, the app supplies malformed input and the kernel processes it without adequately constraining the read.

3. Payload / execution method (class level): The payload is crafted input to the vulnerable interface. The disclosed data is returned to the calling app as part of the operation's output—consistent with the description "an app may be able to disclose kernel memory." No memory-write or control-flow primitive is involved; the effect is a read leak. Attempting the operation may simply return over-read bytes rather than crash the process, since AC is Low.

4. Post-exploitation impact: The app obtains kernel memory contents. Due to C:H and I:N/A:N, the impact is limited to confidentiality: leak of kernel-resident data that can include addresses or other sensitive bytes. This can be combined with a separate memory-corruption vulnerability to defeat ASLR or to exfiltrate kernel secrets, but CVE-2026-86903 alone does not yield code execution or persistence. An attacker may repeat the primitive to aggregate leaked memory over time.

Impact Assessment

Business impact centers on loss of confidentiality of kernel memory on managed Apple endpoints (iPhones, iPads, Macs running macOS Golden Gate, Apple TV, Vision Pro, Apple Watch). Affected systems are any device running a version prior to the patched releases listed by NVD. CVSS 5.5 (Medium) reflects a local, low-complexity, low-privilege, no-user-interaction read primitive with High confidentiality impact and no integrity/availability impact. Blast radius is bounded by the requirement for local code execution; there is no remote, unauthenticated network exposure described. The principal enterprise risk is defense-in-depth erosion: kernel information disclosure can be chained with other vulnerabilities, and the leaked memory may contain sensitive data. EPSS 0.00116 (1.8th percentile) and the absence of a CISA KEV entry indicate low near-term exploitation likelihood and no known active exploitation. Severity for prioritization purposes is best treated as medium—remediate on a standard cycle, accelerated only if the endpoint fleet is exposed to untrusted apps (e.g., sideloading, BYOD, or high-value targets).

Detection Guidance

Note: Because the vulnerable interface (subsystem, syscall, IOUserClient, or driver) is unspecified in the source data, the rules below detect exploitation at the conceptual level—abnormal attempts to read or acquire kernel memory from user space and post-disclosure behaviors—rather than targeting a named API.

Sigma Rule

title: Potential Kernel Memory Disclosure Exploitation Attempt (CVE-2026-86903)
id: 8f2c1a44-9d3e-4b77-a1c2-7e6f0b9d2a10
status: experimental
description: Detects process behavior consistent with a local app attempting to disclose kernel memory via insufficient input validation on unpatched Apple operating systems.
references:
  - https://nvd.nist.gov/vuln/detail/CVE-2026-86903
author: valtersit.com
date: 2026/01/01
logsource:
  product: macos
  category: process_creation
detection:
  selection_utils:
    Image|endswith:
      - '/dtrace'
      - '/sysctl'
      - '/kextstat'
      - '/ioreg'
      - '/ioclass'
  selection_args:
    CommandLine|contains:
      - 'IOKit'
      - 'IOService'
      - 'kernel'
      - 'kalloc'
      - 'kmem'
  condition: selection_utils and selection_args
falsepositives:
  - Legitimate developer or diagnostic tooling
  - Performance and kernel debugging utilities
level: low
tags:
  - attack.t1068
  - cve.2026.86903

YARA Rule

rule CVE_2026_86903_Kernel_Memory_Disclosure_Indicators
{
    meta:
        description = "Heuristic indicators for local apps probing kernel input-validation surfaces associated with CVE-2026-86903 (out-of-bounds read / kernel memory disclosure)"
        author = "valtersit.com"
        date = "2026-01-01"
        reference = "https://nvd.nist.gov/vuln/detail/CVE-2026-86903"
        cwe = "CWE-125"
        severity = "medium"
    strings:
        $a1 = "kernel memory" ascii nocase
        $a2 = "kernel_task" ascii
        $a3 = "OOB read" ascii nocase
        $a4 = "out-of-bounds" ascii nocase
        $a5 = "IOServiceOpen" ascii
        $a6 = "IOConnectCallMethod" ascii
        $a7 = "info leak" ascii nocase
    condition:
        uint32be(0) == 0xFEEDFACE or uint32be(0) == 0xFEEDFACF or uint32be(0) == 0xCAFEBABE
        and 2 of ($a*)
}

Suricata IDS Rule

alert tcp $HOME_NET any -> $EXTERNAL_NET any (msg:"CVE-2026-86903 Possible Kernel Memory Disclosure Exfiltration (Apple iOS/iPadOS/macOS)"; flow:established,to_server; content:"|00 00 00 00|"; depth:4; dsize:>512; threshold:type limit, track by_src, count 5, seconds 60; classtype:attempted-recon; reference:cve,2026-86903; reference:url,nvd.nist.gov/vuln/detail/CVE-2026-86903; metadata:affected_product Apple_iOS_iPadOS_macOS, attack_target Client_Endpoint, created_at 2026_01_01, signature_severity Minor, tag CVE_2026_86903; sid:202686903; rev:1;)

Elastic Detection

process where event.type == "start" and
  process.name in ("ioreg", "ioclass", "sysctl", "kextstat", "dtrace") and
  process.command_line like~ ("*IOKit*", "*IOService*", "*kernel*", "*kmem*")

Splunk SPL Query

index=endpoint sourcetype=osquery OR sourcetype=sysmon OR sourcetype=edr
| search (process_name IN ("ioreg","ioclass","sysctl","kextstat","dtrace") OR command_line="*IOKit*" OR command_line="*kernel*")
| eval cve="CVE-2026-86903"
| stats count min(_time) as first_seen max(_time) as last_seen values(command_line) as cmds by host process_name user
| where count > 3
| sort - count

Wazuh OSSEC Rule

<group name="apple,kernel_memory_disclosure,CVE-2026-86903,">
  <rule id="100903" level="6">
    <decoded_as>json</decoded_as>
    <field name="event.type">process_start</field>
    <field name="process.name">ioreg|ioclass|sysctl|kextstat|dtrace</field>
    <description>CVE-2026-86903: Suspicious kernel inspection utility executed - possible kernel memory disclosure attempt</description>
    <mitre>
      <id>T1068</id>
    </mitre>
    <group>cve_2026_86903,</group>
  </rule>
</group>

Mitigation & Patch Guidance

Patch confidence: 2/4 (CLAIMED — single source (NVD) claims the fix; not independently confirmed against a vendor security advisory at time of writing).

1. Immediate mitigations:

   • Where immediate patching is impossible, restrict installation of untrusted or sideloaded applications and enforce device management policies that block unvetted app sources; the flaw requires local app execution.
   • Apply MDM restrictions to disable or limit developer/diagnostic tooling on production endpoints.
   • Monitor for anomalous local app behavior consistent with the detection rules above.
   • Note: NVD lists no vendor-supplied workaround; no workaround is provided in the source data.

2. Patch / upgrade steps:

   • Upgrade to the fixed releases: iOS 27, iPadOS 27, macOS Golden Gate 27, tvOS 27, visionOS 27, and watchOS 27.
   • Roll across the fleet via MDM/automated update channels; prioritize high-value targets and BYOD devices with sideloading enabled.
   • Verify version state post-upgrade and track any devices unable to update.

3. Long-term hardening:

   • Maintain rapid OS update SLAs for Apple endpoints, since kernel memory disclosure primitives are commonly used as enablers for chained exploits.
   • Restrict sideloading and unmanaged app installation through MDM supervision.
   • Monitor CISA KEV and EPSS for changes; if exploitation evidence appears, accelerate remediation.
   • Track the CVE for an independent vendor advisory to raise patch confidence from CLAIMED (2/4) to confirmed.

References

• NVD — CVE-2026-86903: https://nvd.nist.gov/vuln/detail/CVE-2026-86903
• CWE-125 Out-of-bounds Read: https://cwe.mitre.org/data/definitions/125.html
• Apple Security Releases (verify fixed versions iOS/iPadOS 27, macOS Golden Gate 27, tvOS 27, visionOS 27, watchOS 27): https://support.apple.com/en-us/HT201222
• FIRST EPSS (score 0.00116): https://www.first.org/epss/
• CISA Known Exploited Vulnerabilities Catalog (CVE-2026-86903 NOT listed as of report date): https://www.cisa.gov/known-exploited-vulnerabilities-catalog

No threat actor campaigns or exploit-in-the-wild evidence are identified in the provided data; presence in CISA KEV: NO.