CriticalCVE-2023-42917

    Apple Multiple Products WebKit Memory Corruption Vulnerability (CVE-2023-42917)

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

    What is affected, what to do

    The vulnerability CVE-2023-42917 allows for remote code execution (RCE) due to a memory corruption issue in Apple iOS, iPadOS, macOS, and Safari WebKit when processing malicious web content. An attacker can execute arbitrary code without authentication, posing a significant risk. The vulnerability is actively exploited, as evidenced by reports of attacks on iOS versions prior to 16.7.1. Affected products include all that use WebKit for HTML processing, such as Apple Safari and non-Apple products. It is urgent to update to iOS 17.1.2, iPadOS 17.1.2, macOS Sonoma 14.1.2, or Safari 17.1.2 to mitigate the risk.

    The vulnerability is being actively exploited; treat it as a priority. Update Apple Safari to version 17.1, Apple macOS to version 14.1, Apple iOS and iPadOS to version 17.1. Immediate actions, mitigation and detection rules are in the runbook below.

    Affected
    • Apple Safari lt *..17.1
    • Apple macOS lt *..14.1
    • Apple iOS and iPadOS lt *..17.1
    Fixed in
    • Apple Safari 17.1
    • Apple macOS 14.1
    • Apple iOS and iPadOS 17.1

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

    9.3 %

    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
    220.68 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
    9.3 %
    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 2 December 2023
    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-787

    Response and mitigation

    Why act now?

    Prioritisation rationale

    The flaw is network-reachable without authentication and only requires the victim to load crafted web content. Successful exploitation fully compromises confidentiality, integrity and availability within the browser process context. Apple confirms exploitation against older iOS releases, and the pattern matches targeted exploit chains against individuals (spyware delivery) rather than mass exploitation; no ransomware use is known. Exploitation likelihood sits in the upper tier of all CVEs. Organisations with a large iOS fleet, exposed executives or critical-infrastructure staff should rate this high to critical and complete fleet-wide patching within 72 hours. Windows-centric estates mainly need to address BYOD and embedded WebKit components.

    1. Runbook step 1

      Immediate response (0-24 h)

      • Force the patch: Push iOS/iPadOS 17.1.2, macOS Sonoma 14.1.2 and Safari 17.1.2 via MDM (Intune, Jamf, Workspace ONE) as mandatory updates with a short deferral window. For older branches, the context lists iOS/iPadOS 16.7.3 and 15.8.1 — verify the mapping in Apple's security advisory.
      • Raise the compliance floor: Bump the minimum OS version in conditional-access and compliance policies now. Non-compliant devices lose access to mail, VPN and SSO until they update.
      • High-value targets first: Update devices belonging to executives, admins, OT/critical-infrastructure staff and frequent travellers first, and enable Lockdown Mode on them. Known exploitation targeted iOS versions before 16.7.1, a profile typical of targeted operations against individuals.
      • Reconcile inventory: Identify every Apple device on an outdated OS, including BYOD with corporate data. Block unmanaged devices from corporate resources or move them to guest access.
      • Find non-Apple WebKit: Inventory Linux hosts running WebKitGTK/WPE WebKit, kiosk and embedded systems, and applications with embedded WebKit views. A patch is available from the vendor — look up the fixed version in the vendor advisory.

    2. Runbook step 2

      Mitigation layers

      • Endpoint hardening: Deploy Lockdown Mode (iOS/iPadOS/macOS) via MDM for exposed user groups. It disables JIT and complex web features, sharply shrinking WebKit attack surface. Note: on iOS/iPadOS every browser (Chrome, Edge, Firefox included) runs on WebKit, so switching browsers there is not a mitigation.
      • macOS browser policy: Until patched, set a non-WebKit browser (Chromium or Gecko) as the default on unpatched Macs. Restrict Safari via configuration profile.
      • Network / secure web gateway: Block or isolate (remote browser isolation) newly registered and uncategorised domains and URL shorteners for mobile devices. Links sent via SMS, iMessage and messengers are the usual delivery path.
      • IAM / least privilege: Enforce device-health-based conditional access. Deny admin portals to mobile devices below the fixed version and shorten session lifetimes.
      • Segmentation: Keep mobile devices in a dedicated Wi-Fi/VLAN segment with no direct reach into management networks or OT zones. A browser-level compromise should not translate into access to critical systems.

    3. Runbook step 3

      Detection rules

      • MDM / vulnerability inventory: Flag devices below OS 17.1.2 or Safari 17.1.2. In Defender, for example: DeviceTvmSoftwareInventory | where SoftwareName has "safari" and SoftwareVersion !startswith "17.1.2" (adapt the version logic to your estate).
      • Proxy / gateway logs: Hunt user agents containing Version/17.0, Version/17.1 or Version/16. alongside Mobile/ or Safari/ to find unpatched clients still reaching corporate services. Splunk starting point: index=proxy http_user_agent="*Safari*" http_user_agent="*Version/17.1 *" | stats dc(src_ip) by http_user_agent.
      • macOS EDR process ancestry: Alert at high severity on children of com.apple.WebKit.WebContent or Safari such as sh, bash, zsh, osascript, curl, or unknown binaries in /tmp or /Users/*/Library. Sigma shape: ParentImage|endswith: 'WebContent' plus an Image|endswith shell list. Correlate with bursts of WebContent crash reports in /Library/Logs/DiagnosticReports/*WebContent*.
      • Mobile forensics on suspicion: For targeted users, run sysdiagnose output or iTunes backups through the Mobile Verification Toolkit (MVT) against current IOC sets. Unexplained crashes or spontaneous reboots right after opening a link warrant investigation.
      • Network telemetry (Zeek/DNS): Hunt DNS lookups from mobile segments to very young domains that are immediately followed by outbound TLS to rare IPs with unusual JA3/JA4 fingerprints.

    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 memory corruption vulnerability was addressed with improved locking. This issue is fixed in iOS 17.1.2 and iPadOS 17.1.2, macOS Sonoma 14.1.2, Safari 17.1.2. Processing web content may lead to arbitrary code execution. Apple is aware of a report that this issue may have been exploited against versions of iOS before iOS 16.7.1.

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

    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
    • < 17.1
    • 17.1
    ApplemacOS
    • < 14.1
    • 14.1
    AppleSafari
    • < 17.1
    • 17.1
    applesafari
    • < 17.1.2
    • 17.1.2
    webkitgtkwebkitgtk\+
    • < 2.42.3
    • 2.42.3
    Distribution and container packages (1)

    Downstream packages (e.g. Bitnami, Debian, Ubuntu, Red Hat). Versions refer to the distribution, not the vendor.

    Distribution and container packages
    Affected versionsFixed in
    bitnamijre
    • 1.9.0
    • —

    Vendors and products

    Affected operating systems

    Affected operating systems
    Linuxdebiandebian_linux11.0
    Linuxdebiandebian_linux12.0
    Linuxdebianwebkit2gtkbookworm
    Linuxdebianwebkit2gtkbullseye
    macOSapplemacos—
    Mobileappleiphone_os—
    Otherfedoraprojectfedora38
    Otherfedoraprojectfedora39
    Otherappleipados—

    Weakness classes (CWE)

    • CWE-787Out-of-bounds Write

      Base

      The product writes data past the end, or before the beginning, of the intended buffer.

      Entry at MITRE CWE-787

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

    References & sources

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