CVE-2016-4655 is an information disclosure vulnerability in Apple iOS. CISA added it to the Known Exploited Vulnerabilities catalogue on 24 May 2022, which means attackers have used it in real attacks. The Apple iOS kernel allows attackers to obtain sensitive information from memory via a crafted application.
What the vulnerability means in iOS
CVE-2016-4655 is an information disclosure issue in Apple iOS, which means the weakness is not direct code execution but unwanted exposure of sensitive data from process memory. In practice, that matters because memory disclosure often reveals fragments of secrets, state, or other data that were never meant to leave the kernel boundary.
For a mobile operating system, kernel memory disclosure is dangerous because the kernel sits close to the most trusted parts of the platform. If an attacker can coerce the system into revealing memory contents, they may learn enough to support follow-on exploitation, evade defences, or recover data that should have remained transient.
How this class of flaw is exploited
The primary issue is that a crafted application can trigger the iOS kernel to return sensitive information. That makes the flaw especially useful to attackers who already have a foothold on the device and want to turn limited app-level execution into broader visibility into the operating system state.
Information disclosure bugs are often valuable as stepping stones. They can expose addresses, internal structures, tokens, or other memory-resident material that weakens platform protections and makes other exploits more reliable. For that reason, a disclosure flaw should never be treated as “just a leak”.
When you need the authoritative record for this issue, use the CVE Program entry model and the NIST National Vulnerability Database as the canonical sources for record details and vulnerability context.
Exposure and remediation considerations
Because the flaw was added to CISA’s KEV catalogue, organisations should treat exposure as operationally significant rather than theoretical. The first question is whether the affected iOS estate still exists in inventory, because unmanaged devices and long-tail mobile fleets are where exploited issues often persist longest.
Remediation starts with vendor guidance and version-specific patching, but teams should also consider compensating controls while remediation is pending. Those controls include restricting untrusted app installation paths, tightening mobile application governance, and reducing the amount of sensitive material retained on endpoints that cannot yet be updated.
For broader vulnerability handling, NHIMG’s Vulnerability Management Guide is a useful companion for asset scoping, KEV prioritisation, and remediation workflow design.
Detection and post-compromise review
Because memory disclosure can be silent, detection usually depends less on a distinctive alert and more on investigating suspicious app behaviour, unusual crash patterns, exploit chaining, or signs that a device has been targeted alongside other iOS weaknesses. If exploitation is suspected, the goal is to assume that data exposed in memory may have been observed or harvested.
Post-patch review should focus on what the leaked memory could have contained and whether any identity material, session state, or application secrets were resident at the time. Even when the vulnerability is fixed, any exposed secret that was in scope for the process or kernel memory should be treated as potentially compromised and reviewed for rotation or replacement.
For mobile disclosure risks and secret exposure patterns, iOS apps leaking hard-coded secrets is directly relevant to the broader problem of sensitive data on Apple devices.
Risk and Threat Considerations
Information disclosure in a mobile kernel is risky because it can turn a single app-level interaction into visibility into protected memory. That can undermine platform trust, help attackers prepare a second-stage exploit, and expose data that was never intended to be user-visible or application-visible.
Failure mechanism: A crafted application induces the kernel to reveal memory contents, allowing an attacker to recover sensitive runtime information and use it to support further compromise or data theft.
Impact: The exposed data may include secrets, session material, internal state, or other sensitive information that increases the chance of device compromise and secondary abuse.
Standards & Framework Alignment
This section maps relevant standards and security frameworks to the operational risks and controls described in this guidance.
CIS Controls v8, NIST SP 800-53 Rev 5 and NIST CSF 2.0 set the technical controls, while ISO/IEC 27001:2022 defines the regulatory obligations.
| Framework | Control / Reference | Relevance |
|---|---|---|
| CIS Controls v8 | CIS-7 — Continuous Vulnerability Management | This CVE requires prioritised vulnerability tracking and remediation on exposed iOS assets. |
| Recommendation — Prioritise KEV-listed iOS flaws and verify remediation across all in-scope mobile devices. | ||
| NIST SP 800-53 Rev 5 | RA-5 — Vulnerability Monitoring and Scanning | The issue depends on identifying affected devices and tracking vulnerable software exposure. |
| SI-2 — Flaw Remediation | This vulnerability requires timely vendor-guided patching and controlled exception handling. | |
| Recommendation — Scan managed iOS assets, confirm exposure, and track remediation to closure. Apply vendor remediation promptly and document any temporary exception with compensating controls. | ||
| NIST CSF 2.0 | DE.CM-08 — Vulnerability Monitoring | The subject calls for continuous awareness of exploitable weaknesses in the device estate. |
| Recommendation — Monitor mobile vulnerability exposure and escalate KEV-listed issues for immediate action. | ||
| ISO/IEC 27001:2022 | A.8.8 — Management of technical vulnerabilities | The page centers on vulnerable software exposure and remediation governance for iOS endpoints. |
| Recommendation — Track, assess, and remediate iOS technical vulnerabilities under a formal process. | ||
Practitioner Guidance
Why practitioners should care: A memory disclosure flaw on a mobile platform should be treated as a data exposure event, not only as a vulnerability-management item. The practical question is which devices remain exposed, what sensitive material could have been resident in memory, and whether that data needs to be replaced or revoked.
Common misunderstanding: Teams sometimes underestimate disclosure bugs because there is no immediate remote code execution. In reality, a well-placed leak can materially lower the cost of exploitation and increase the blast radius of any later compromise.
Practitioner takeaway: Prioritise exposed iOS assets through KEV-based triage, validate patch coverage, and review whether any credentials, tokens, or other sensitive artefacts could have been present in memory during exploitation.