CVE-2026-84531 in iOS
Summary
by MITRE • 09/15/2026
An out-of-bounds write issue was addressed with improved bounds checking. This issue is fixed in iOS 27 and iPadOS 27, macOS Golden Gate 27. Processing maliciously crafted NTLM input may lead to unexpected app termination.
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Analysis
by VulDB Data Team • 09/15/2026
The vulnerability described involves an out-of-bounds write condition within the system components responsible for processing Network Level Authentication (NTLM) inputs on iOS and iPadOS version 27, as well as macOS Golden Gate version 27. This type of memory corruption error typically arises when a software application writes data to a memory location that falls outside the boundaries of the intended buffer or array. In this specific context, the flaw is triggered by processing maliciously crafted NTLM input sequences. The root cause lies in insufficient validation and bounds checking mechanisms within the authentication handling logic, which fails to verify whether the incoming data length aligns with the allocated memory space before performing write operations.
From a technical perspective, out-of-bounds writes are among the most dangerous classes of software vulnerabilities because they can lead to arbitrary code execution, denial of service, or privilege escalation depending on how the corrupted memory is utilized by subsequent processes. In this instance, the immediate operational impact manifests as unexpected application termination. This indicates that while the exploitability for remote code execution may depend on further exploitation steps not detailed in the summary, the vulnerability reliably causes a crash when triggered with specific malformed inputs. Such crashes disrupt normal system operations and can be leveraged to cause denial of service against services relying on NTLM authentication or related network stack components.
This issue is categorized under CWE-787: Out-of-bounds Write within standard vulnerability classification frameworks, which highlights the critical nature of memory safety violations in modern operating systems. Furthermore, from a threat actor perspective, this flaw aligns with techniques associated with ATT&CK ID T1059, specifically command and script interpreter abuse or potentially T1203 if used for exploitation phases involving client-side attacks. The ability to trigger crashes through crafted network inputs suggests that an attacker could use this vulnerability in targeted phishing campaigns or man-in-the-middle scenarios where NTLM authentication is negotiated, aiming to destabilize the target device or gather information about system behavior during crash states.
Apple has addressed this security issue by implementing improved bounds checking within the affected components for iOS 27, iPadOS 27, and macOS Golden Gate 27. These updates ensure that input data is rigorously validated against expected limits before any memory allocation or write operations are executed. To mitigate risks associated with similar vulnerabilities in legacy systems or environments where immediate patching is not feasible, administrators should enforce strict network segmentation to limit exposure of authentication services to untrusted networks. Additionally, deploying intrusion detection systems capable of identifying malformed NTLM packets can provide an additional layer of defense by blocking malicious inputs before they reach the vulnerable application logic. Users are strongly advised to update their devices to the latest supported versions to ensure these memory safety protections are active and effective against potential exploitation attempts.