CVE-2026-103264 in Fleet
Summary
by MITRE • 10/01/2026
Fleet versions before 4.87.0 contain an authentication bypass vulnerability in the device API that accepts hostnames and hardware serials as authentication tokens in addition to device UUIDs. Unauthenticated attackers who know or guess these non-secret identifiers can authenticate as iOS/iPadOS hosts to read device data and trigger device-scoped actions including software installation and MDM migration.
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Analysis
by VulDB Data Team • 10/01/2026
The vulnerability identified within Fleet versions prior to 4.87.0 represents a critical authentication bypass flaw located in the device API endpoint responsible for handling host identification tokens. This specific component was designed to accept multiple forms of identifiers as valid authentication credentials, including standard device UUIDs alongside less secure identifiers such as hostnames and hardware serial numbers. The fundamental technical failure lies in the system's inability to distinguish between secret-based authentication mechanisms and public or easily discoverable identifier strings. By treating these non-secret identifiers with equal weight to cryptographic tokens or unique universal identifiers, the application fails to enforce proper access control policies that require proof of possession rather than mere knowledge of an identifier. This architectural oversight allows any actor who can observe network traffic, extract configuration files, or otherwise obtain a device's hostname or serial number to impersonate that specific iOS or iPadOS host within the Fleet management console.
From a technical perspective, this flaw aligns with CWE-287, which describes Improper Authentication, specifically where an entity is able to assume the identity of another without providing sufficient proof of its own identity. The vulnerability exploits the fact that hardware serial numbers and network hostnames are often static, non-randomized values that can be enumerated or intercepted through standard IT operations, log analysis, or even physical access to managed devices. Unlike UUIDs which are typically generated randomly and uniquely per device instance, serial numbers and hostnames may follow predictable patterns or remain constant across deployments, making them susceptible to brute-force guessing attacks if the attacker has partial knowledge of the naming conventions used by the organization. The API endpoint's logic accepts these values as valid session tokens without verifying their secrecy or integrity, effectively rendering the authentication mechanism null for any identifier that is not kept confidential.
The operational impact of this vulnerability is severe due to the high-privilege nature of MDM (Mobile Device Management) operations. An unauthenticated attacker who successfully authenticates using a guessed hostname or serial number gains full control over the targeted iOS or iPadOS device within the Fleet ecosystem. This access level permits the reading of sensitive device data, which may include user information, application lists, and configuration profiles. More critically, it allows the execution of device-scoped actions that can compromise the integrity and availability of the managed endpoint. These malicious actions range from installing unauthorized software packages to triggering MDM migrations, which could redirect management control away from the organization's secure infrastructure to an attacker-controlled server. This capability effectively neutralizes the security boundaries established by the mobile device management solution, allowing for persistent access and potential lateral movement within the corporate network if the managed devices are connected to internal resources.
This vulnerability is also indicative of ATT&CK technique T1078, Valid Accounts, where adversaries use legitimate credentials or identifiers to bypass authentication controls. In this context, the valid account is represented by the device identity itself, which is being misused due to weak validation logic. The exploitation path typically involves reconnaissance to identify target devices and their associated hostnames or serial numbers, followed by direct API calls that mimic legitimate management traffic. Because the attack does not require password cracking or credential theft in the traditional sense, it bypasses many standard security monitoring tools that focus on failed login attempts or anomalous user behavior rather than valid but unauthorized device impersonation.
To mitigate this vulnerability, organizations running Fleet versions before 4.87.0 must immediately upgrade to version 4.87.0 or later, where the authentication logic has been corrected to reject non-secret identifiers for API access. Until an upgrade is performed, administrators should implement network-level controls such as firewall rules that restrict access to the affected API endpoints only from trusted IP addresses associated with known management servers. Additionally, rotating device hostnames and ensuring serial numbers are not exposed in publicly accessible logs or documentation can reduce the attack surface by making enumeration more difficult. It is also recommended to audit existing API usage logs for any signs of unauthorized authentication attempts using hostname or serial number tokens, as these may indicate active exploitation. Implementing strict input validation that enforces UUID-only formats for device identification in untrusted contexts would further harden the system against similar future flaws.