CriticalCVE-2023-23529

    Apple Multiple Products WebKit Type Confusion Vulnerability (CVE-2023-23529)

    Published In CISA KEV since Sources: SingCERT, Debian, pwn.watch, CVE.org, Red Hat

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    What is affected, what to do

    A type confusion vulnerability in Apple WebKit allows code execution when processing malicious web content, affecting iOS, macOS, Safari, and iPadOS. This impacts both Apple and non-Apple products using WebKit for HTML parsing. The vulnerability is actively exploited, as confirmed by reports. Affected versions include iOS 15.7.4, iPadOS 15.7.4, iOS 16.3.1, iPadOS 16.3.1, macOS Ventura 13.2.1, and Safari 16.3. Immediate patching to the specified versions is critical.

    The vulnerability is being actively exploited; treat it as a priority. Update Apple iOS and iPadOS to version 16.3, Apple Safari to version 16.3, Apple macOS to version 13.2. Immediate actions, mitigation and detection rules are in the runbook below.

    Affected
    • Apple iOS and iPadOS lt *..16.3
    • Apple Safari lt *..16.3
    • Apple macOS lt *..13.2
    • Apple iOS and iPadOS lt *..15.7
    Fixed in
    • Apple iOS and iPadOS 16.3
    • Apple Safari 16.3
    • Apple macOS 13.2
    • Apple iOS and iPadOS 15.7

    Not sure whether and how you are affected? Ask a question about this vulnerability

    Metrics

    8.8

    Priority

    XIEM Effective CVSS: highest available CVSS rating from NVD and vendor data.

    Source: NVD, CVSS v3

    8.8

    CVSS v3

    Severity High on the scale from 0 to 10.

    Source: SingCERT, Debian, pwn.watch, CVE.org, Red Hat

    9.4 %

    EPSS score

    Moderate — model estimates 1-10% exploitation likelihood.

    Source: FIRST EPSS, percentile 95.4

    Show all metrics
    Severity
    Critical
    Priority (0–325)

    The priority score is a consolidated metric that condenses several individual signals into a single, action-guiding ranking: technical severity (CVSS), exploitation likelihood (EPSS), known-exploited status (KEV) and the context of the affected asset. The aim is to answer the only truly important question in vulnerability management: what first?

    Read in glossary
    219.08 Methodology
    Exploit maturity

    An exploit is code or a technique that specifically uses a concrete vulnerability to force unintended behaviour — such as executing code or escalating privileges. It is the tool that turns a theoretical flaw into a practical attack.

    Read in glossary
    actively exploitedSource: Apple (CVE.org), CSA/SingCERT How we classify
    XIEM Effective CVSS

    XIEM® is the tiered managed-security operating model from NEOSEC and a registered trademark of NEOSEC GmbH. It extends classic SIEM — the central collection, normalisation and correlation of security-relevant events — with endpoint forensics, network visibility and deception technology, and consolidates them into three building tiers: Sentry, Orchestrate and Command.

    Read in glossary
    8.8 Methodology
    CVSS v3

    CVSS is the globally established, open standard for assessing the technical severity of a vulnerability on a scale from 0 to 10. It describes how easily a flaw can be exploited and what damage it can cause — but not how likely its actual exploitation is. CVSS and the complementary EPSS deliberately answer different questions.

    Read in glossary
    8.8
    EPSS score

    The EPSS score is the absolute model output for an individual vulnerability: the estimated probability of real-world exploitation within the next 30 days, expressed as a value between 0 and 1 (i.e. 0 % to 100 %). A score of 0.42 means „the model estimates a 42 % chance of real-world exploitation within 30 days“.

    Read in glossary
    9.4 %
    Moderate — model estimates 1-10% exploitation likelihood.
    EPSS percentile

    The EPSS percentile is the relative position of a vulnerability within all EPSS-scored CVEs, expressed as a value between 0 and 1. A percentile of 0.90 means „this CVE has a higher EPSS score than 90 % of all other scored CVEs“. Unlike the EPSS score, it is not a probability — but a positioning within a ranking.

    Read in glossary
    95.4
    Critical — this CVE ranks in the top fifth of all CVEs scored today (rank ≥ 80%).
    KEV status

    The KEV catalogue is a list maintained by the US authority CISA of vulnerabilities for which active exploitation in the wild has been confirmed. It answers not the question „how severe?“ but „is it already being attacked?“ — thereby sharply prioritising patching.

    Read in glossary
    Actively exploited
    Published
    In CISA KEV since

    The KEV catalogue is a list maintained by the US authority CISA of vulnerabilities for which active exploitation in the wild has been confirmed. It answers not the question „how severe?“ but „is it already being attacked?“ — thereby sharply prioritising patching.

    Read in glossary
    CISA assessment (SSVC)
    Exploitation: active · not automatable · Technical impact: total
    Source: CISA Vulnrichment, as of 28 January 2025
    CWE

    CWE is a catalogue of typical weakness types in software and hardware — such as flawed input validation, unsafe memory handling or poor authentication. Where a CVE names a concrete vulnerability in a concrete product, a CWE describes the underlying class of defect.

    Read in glossary
    CWE-843

    Response and mitigation

    Why act now?

    Prioritisation rationale

    This flaw was exploited as a zero-day against Apple devices. It is network-reachable without authentication and only requires the victim to load crafted web content, for example via a link in email, a messenger or SMS. Bugs like this typically serve as the initial stage of exploit chains against selected high-value individuals rather than mass campaigns. CISA does not flag ransomware use, but exploitation likelihood is rated high. Organisations with a large iOS/macOS fleet, exposed leadership or a critical-infrastructure footprint should treat this as a high-priority patch with a 48-hour target. Predominantly Windows estates can use their standard expedited cycle, provided Conditional Access blocks outdated Apple devices.

    1. Runbook step 1

      Immediate response (0-24 h)

      • Enforce patches via MDM: Deploy iOS/iPadOS 16.3.1 or 15.7.4 (for devices that cannot move to 16), macOS Ventura 13.2.1, and Safari 16.3 on older macOS releases. Set a hard update deadline with forced restart in Jamf, Intune or Kandji. The vulnerable WebKit process remains loaded until reboot.
      • Pull an inventory: Run an MDM compliance report covering OS and Safari versions on every Apple endpoint. Flag anything below the fixed builds as non-compliant and block it from M365, VPN and internal web apps via Conditional Access until it is updated.
      • Prioritise high-value users: Patch executives, admins, legal and press staff, and frequent travellers first. WebKit zero-days are typically aimed at specific individuals.
      • Hunt for non-Apple WebKit: Identify Linux hosts and appliances using WebKitGTK/WPE WebKit, as well as kiosk and embedded systems. The patch is available from the respective vendor — check the vendor advisory for the fixed version.
      • Handle legacy hardware: Remove unsupported devices that cannot reach iOS 15.7.4 or 16.3.1 from the corporate network, or confine them to guest Wi-Fi with no internal access.

    2. Runbook step 2

      Mitigation layers

      • Endpoint hardening: Enable Lockdown Mode for at-risk users (iOS 16, macOS Ventura). It disables JIT and other complex web features in WebKit, which sharply reduces the attack surface for type-confusion exploits.
      • Browser fallback on macOS: Make a Chromium- or Firefox-based browser the default until patching completes. Note that every browser on iOS/iPadOS is forced onto WebKit, so switching browsers offers no protection there.
      • Network layer: Use a web proxy or SWG with reputation filtering, and block newly registered domains and "uncategorised" sites. Push DNS filtering to mobile devices via an MDM profile (per-app VPN or DNS Settings payload).
      • Mail and messaging: Enable URL rewriting and detonation sandboxing for links. Exploitation requires the user to open crafted content, so link-based delivery is the main vector. Restrict remote content loading in Apple Mail via a configuration profile.
      • Access control: Make device-posture Conditional Access with minimum OS versions (iOS 16.3.1, macOS 13.2.1) a permanent policy rather than a one-off response.

    3. Runbook step 3

      Detection rules

      • EDR process ancestry (macOS): Child processes spawned by the WebKit renderer are a strong signal. Example KQL: DeviceProcessEvents | where InitiatingProcessFileName startswith "com.apple.WebKit.WebContent" and FileName in~ ("sh","bash","zsh","osascript","curl","python3").
      • Crash patterns: Clusters of com.apple.WebKit.WebContent crashes with EXC_BAD_ACCESS in JavaScriptCore can indicate failed exploit attempts. Look in /Library/Logs/DiagnosticReports and ~/Library/Logs/DiagnosticReports on macOS, and in sysdiagnose analytics data on iOS.
      • File and persistence indicators (macOS): A Sigma-style rule can flag executable files written to ~/Library/LaunchAgents or /tmp within 5 minutes of Safari or a WebContent process starting (ESF/EDR file events).
      • Network telemetry: In proxy or Zeek logs (http.log, ssl.log), look for Apple user agents hitting low-reputation or first-seen domains, followed by anomalous outbound traffic from the same device. Correlate on source IP and time window.
      • Mobile forensics on suspicion: Run an iTunes backup or sysdiagnose from affected users through the Mobile Verification Toolkit (MVT) against public IOC sets.

    Detection rules

    No NEOSEC detection rule is available for this vulnerability yet.

    Classification under NIS2 and CRA

    Rule-based classification from exploitation status and severity. It does not replace a case-by-case assessment.

    NIS2

    NIS2 is EU Directive (EU) 2022/2555 to raise the level of cybersecurity across the Union. It substantially broadens obligations compared with the first NIS directive: more sectors, mandatory risk management, staged reporting duties and personal accountability of senior management.

    Read in glossary
    Actively exploited: treat the vulnerability as a priority in vulnerability handling under Art. 21(2)(e) NIS2. If it is exploited in your environment, check the reporting obligation under Art. 23 (early warning within 24 hours).
    CRA

    The CRA is EU Regulation (EU) 2024/2847 setting horizontal cybersecurity requirements for „products with digital elements“ — from industrial controllers and software to connected consumer devices. For the first time manufacturers must ensure security across the entire product lifecycle, handle vulnerabilities and provide security updates.

    Read in glossary
    Since 11.09.2026, manufacturers of affected products with digital elements must report actively exploited vulnerabilities under Art. 14 CRA, with an early warning within 24 hours via ENISA's single reporting platform.
    ISO/IEC 27001

    ISO/IEC 27001 is the internationally leading standard for an information security management system (ISMS). It describes a risk-based, process-oriented framework to systematically plan, implement, review and improve information security.

    Read in glossary
    Control A.8.8, management of technical vulnerabilities: assess relevance to your systems, plan remediation and keep evidence.

    Description

    A type confusion issue was addressed with improved checks. This issue is fixed in iOS 15.7.4 and iPadOS 15.7.4, iOS 16.3.1 and iPadOS 16.3.1, macOS Ventura 13.2.1, Safari 16.3. Processing maliciously crafted web content may lead to arbitrary code execution. Apple is aware of a report that this issue may have been actively exploited.

    Source: CSA/SingCERT, Debian Security Advisories, pwn.watch, NVD (NIST), cvelistv5, CISA KEV Catalog, CVE.org (MITRE), redhat_csaf

    Affected products

    The following versions are affected. Older releases of the same product line are also vulnerable unless stated otherwise.

    Affected products
    Affected versionsFixed in
    AppleiOS and iPadOS
    • < 15.7
    • < 16.3
    • 15.7
    • 16.3
    ApplemacOS
    • < 13.2
    • 13.2
    AppleSafari
    • < 16.3
    • 16.3
    applesafari
    • < 16.3
    • 16.3

    Vendors and products

    Affected operating systems

    Affected operating systems
    Linuxdebianwebkit2gtkbullseye
    Linuxdebianwpewebkitbullseye
    macOSapplemacos—
    Mobileappleiphone_os—
    Otherappleipados—

    Weakness classes (CWE)

    • CWE-843Access of Resource Using Incompatible Type ('Type Confusion')

      Base

      The product allocates or initializes a resource such as a pointer, object, or variable using one type, but it later accesses that resource using a type that is incompatible with the original type.

      Entry at MITRE CWE-843

    Public exploit references

    Publicly reported proof-of-concepts, exploit modules and detection templates for this vulnerability. NEOSEC links to the original sources only and does not provide any exploit code.

    Public exploit references
    Apple (CVE.org)CVE.org (MITRE) (opens in a new tab)actively exploited
    CISA KEV CatalogCISA Known Exploited Vulnerability (opens in a new tab)cisa.govactively exploited
    CSA/SingCERTActive Exploitation of Zero-Day Vulnerability in Apple Products (opens in a new tab)CSA/SingCERTactively exploited

    References & sources

    • support.apple.comen-us/HT213635Release notes, Vendor advisory
    • support.apple.comen-us/HT213638Release notes, Vendor advisory
    • support.apple.comen-us/HT213633Release notes, Vendor advisory
    • support.apple.comen-us/HT213673Release notes, Vendor advisory
    • cisa.govknown-exploited-vulnerabilities-catalog?field_cve=CVE-2023-23529government-resource, US government resource
    • pwn.watchpwn.watch: Apple Multiple Products: WebKit Type Confusion (CVE-2023-23529)pwn-watch
    • support.apple.comVendor advisory: Apple Multiple Productspwn-watch
    • NVD (NIST)NVD: CVE-2023-23529pwn-watch
    • cisa.govCISA Known Exploited Vulnerabilities Catalogpwn-watch
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