CriticalCVE-2021-30860

    Apple Multiple Products Integer Overflow Vulnerability (CVE-2021-30860)

    Published In CISA KEV since Sources: SingCERT, CVE.org

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    What is affected, what to do

    An integer overflow was addressed with improved input validation. This issue is fixed in Security Update 2021-005 Catalina, iOS 14.8 and iPadOS 14.8, macOS Big Sur 11.6, watchOS 7.6.2.

    The vulnerability is being actively exploited; treat it as a priority. Update Apple macOS to version 11.6, Apple macOS to version 2021-005, Apple watchOS to version 7.6. Immediate actions, mitigation and detection rules are in the runbook below.

    Affected
    • Apple macOS lt *..11.6
    • Apple macOS lt *..2021-005
    • Apple watchOS lt *..7.6
    • Apple iOS lt *..14.8
    Fixed in
    • Apple macOS 11.6
    • Apple macOS 2021-005
    • Apple watchOS 7.6
    • Apple iOS 14.8

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

    Metrics

    7.8

    Priority

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

    Source: NVD, CVSS v3

    7.8

    CVSS v3

    Severity High on the scale from 0 to 10.

    Source: SingCERT, CVE.org

    76.0 %

    EPSS score

    High — model estimates ≥ 50% chance of real-world exploitation within 30 days.

    Source: FIRST EPSS, percentile 99.53

    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
    218.25 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
    7.8 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
    7.8
    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
    76.0 %
    High — model estimates ≥ 50% chance of real-world exploitation within 30 days.
    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
    99.53
    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 5 February 2024
    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-190

    Response and mitigation

    Why act now?

    Prioritisation rationale

    FORCEDENTRY is on KEV because this CoreGraphics PDF-parsing flaw was weaponised as a zero-click chain delivered through messaging attachments. The CVSS vector lists a local vector with user interaction, but in practice simply receiving a crafted file was enough for full code execution. Targets are typically high-value individuals: executives, journalists, lawyers, activists and government officials. CISA does not flag ransomware use. Exploitation likelihood is very high, among the highest of any CVE. For KRITIS and NIS2 organisations, treat this as high priority wherever unpatched or unmanaged Apple devices belong to key personnel. With full MDM compliance verified, continuous monitoring is sufficient.

    1. Runbook step 1

      Immediate response (0-24 h)

      • Enforce patch levels via MDM: iOS/iPadOS 14.8 or later (legacy devices that cannot run iOS 14: iOS 12.5.5), macOS Big Sur 11.6, macOS Catalina with Security Update 2021-005, and watchOS 7.6.2. Set a minimum-OS compliance policy in Intune, Jamf or Workspace ONE. Non-compliant devices then lose mail, VPN and SSO access automatically through Conditional Access.
      • Inventory within the first hour: Export every Apple device and its OS build from MDM to find the gaps. Separately list unmanaged BYOD devices that reach corporate data via ActiveSync or Graph. Prioritise executives, legal, comms, control-room staff and OT administrators.
      • Retire unpatchable hardware: Any device that cannot reach one of the fixed versions is cut off from the corporate network and corporate data. This includes kiosk iPads in control rooms.
      • Protect high-risk users until the patch is confirmed: Have them temporarily disable iMessage and FaceTime and avoid opening PDF or image attachments from unknown senders. On current iOS and macOS releases, enable Lockdown Mode for exposed individuals.
      • Preserve evidence before reimaging: If compromise is suspected, take an encrypted Finder/iTunes backup and a sysdiagnose and run forensics first, then patch or rebuild. Updating alone may not remove persistence. Afterwards, rotate the user's credentials and tokens (SSO, mail, messengers).

    2. Runbook step 2

      Mitigation layers

      • IAM / access control: Tie Conditional Access to MDM compliance with a minimum OS version. Give unmanaged devices browser-only access with downloads blocked (app protection policies, MAM).
      • Mail and content filtering: Have the mail gateway or sandbox flag PDFs containing /JBIG2Decode streams. Also flag files whose extension (.gif, .jpg) contradicts %PDF magic bytes, so you filter on true file type rather than extension. A YARA idea for this: $pdf = "%PDF" at 0 combined with $j = "/JBIG2Decode" and extension not equal to .pdf.
      • Network segmentation: Put mobile devices on a dedicated Wi-Fi/VLAN with no direct path to management networks, OT or admin jump hosts. Route egress through a DNS-filtering proxy that applies spyware-infrastructure blocklists and blocks newly registered domains.
      • macOS endpoint hardening: Deploy EDR to every Mac and enforce SIP and Gatekeeper via configuration profile. Enable automatic security updates (Rapid Security Responses, XProtect) and remove local admin rights.
      • Organisational: Give high-risk staff a separate, minimal corporate device. Add mobile-device incident reporting to the ISMS (ISO 27001 A.5.24–A.5.26).

    3. Runbook step 3

      Detection rules

      • MDM telemetry: Run a daily query for devices below iOS/iPadOS 14.8, below Big Sur 11.6, or on Catalina without 2021-005. Treat newly non-compliant devices as incidents, not routine tickets.
      • Mobile forensics: Scan suspect backups with the Mobile Verification Toolkit (mvt-ios check-backup --iocs <stix2>) against public FORCEDENTRY and spyware IOC sets. Look for anomalies in DataUsage.sqlite, unknown process names, and crash logs from messaging or image-processing components shortly after attachments arrived.
      • Mail gateway and proxy logs: Hunt for PDF content with a mismatched extension and embedded JBIG2 streams. A Sigma shape: selection: file_magic: 'PDF' and file_ext|endswith: ['.gif','.jpg','.png'].
      • macOS EDR: Alert on PDF or image renderers (Preview, QuickLook, mail helpers) spawning shells or script interpreters. KQL: DeviceProcessEvents | where InitiatingProcessFileName in~ ("Preview","QuickLookUIService","com.apple.quicklook.ThumbnailsAgent") and FileName in~ ("sh","bash","zsh","osascript","curl").
      • Network telemetry (Zeek/Suricata): In the mobile segment, watch for DNS lookups to short-lived or newly registered domains and unusual outbound TLS to destinations outside Apple or MDM infrastructure. Correlate on JA3/JA4 and SNI.

    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

    An integer overflow was addressed with improved input validation. This issue is fixed in Security Update 2021-005 Catalina, iOS 14.8 and iPadOS 14.8, macOS Big Sur 11.6, watchOS 7.6.2. Processing a maliciously crafted PDF may lead to arbitrary code execution. Apple is aware of a report that this issue may have been actively exploited.

    Source: CSA/SingCERT, NVD (NIST), cvelistv5, CISA KEV Catalog, CVE.org (MITRE)

    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
    • < 14.8
    • 14.8
    ApplemacOS
    • < 2021-005
    • < 11.6
    • 2021-005
    • 11.6
    ApplewatchOS
    • < 7.6
    • 7.6
    freedesktoppoppler
    • < 22.09.0
    • 22.09.0
    xpdfreaderxpdf
    • < 4.04
    • 4.04

    Vendors and products

    Affected operating systems

    Affected operating systems
    macOSapplemac_os_x10.15.7
    macOSapplemac_os_x—
    macOSapplemacos—
    Mobileappleiphone_os—
    Otherappleipados—
    Otherapplewatchos—

    Weakness classes (CWE)

    • CWE-190Integer Overflow or Wraparound

      Base

      The product performs a calculation that can produce an integer overflow or wraparound when the logic assumes that the resulting value will always be larger than the original value. This occurs when an integer value is incremented to a value that is too large to store in the associated representation. When this occurs, the value may become a very small or negative number.

      Entry at MITRE CWE-190

    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/SingCERTVulnerabilities in Apple iOS, iPadOS, MacOS and WatchOS (opens in a new tab)CSA/SingCERTactively exploited

    References & sources

    • support.apple.comen-us/HT212804x_refsource_MISC, Vendor advisory
    • support.apple.comen-us/HT212805x_refsource_MISC, Vendor advisory
    • support.apple.comen-us/HT212807x_refsource_MISC, Vendor advisory
    • support.apple.comen-us/HT212806x_refsource_MISC, Vendor advisory
    • seclists.org20210917 APPLE-SA-2021-09-13-4 Security Update 2021-005 CatalinaMailing list, x_refsource_FULLDISC, Mailing list, Third-party advisory
    • seclists.org20210917 APPLE-SA-2021-09-13-3 macOS Big Sur 11.6Mailing list, x_refsource_FULLDISC, Mailing list, Third-party advisory
    • seclists.org20210917 APPLE-SA-2021-09-13-1 iOS 14.8 and iPadOS 14.8Mailing list, x_refsource_FULLDISC, Mailing list, Third-party advisory
    • seclists.org20210917 APPLE-SA-2021-09-13-2 watchOS 7.6.2Mailing list, x_refsource_FULLDISC, Mailing list, Third-party advisory
    • seclists.org20210921 APPLE-SA-2021-09-20-8 Additional information for APPLE-SA-2021-09-13-4 Security Update 2021-005 CatalinaMailing list, x_refsource_FULLDISC, Mailing list, Third-party advisory
    • seclists.org20210921 APPLE-SA-2021-09-20-6 Additional information for APPLE-SA-2021-09-13-1 iOS 14.8 and iPadOS 14.8Mailing list, x_refsource_FULLDISC, Mailing list, Third-party advisory
    • seclists.org20210921 APPLE-SA-2021-09-20-7 Additional information for APPLE-SA-2021-09-13-3 macOS Big Sur 11.6Mailing list, x_refsource_FULLDISC, Mailing list, Third-party advisory
    • support.apple.comkb/HT212824x_refsource_CONFIRM, Vendor advisory
    • seclists.org20210924 APPLE-SA-2021-09-23-1 iOS 12.5.5Mailing list, x_refsource_FULLDISC, Mailing list, Third-party advisory
    • openwall.com[oss-security] 20220902 JBIG2 integer overflow fixed in Xpdf 4.04, Poppler 22.09.0Mailing list, x_refsource_MLIST, Mailing list
    • security.gentoo.orgGLSA-202209-21Vendor advisory, x_refsource_GENTOO, Third-party advisory
    • cisa.govknown-exploited-vulnerabilities-catalog?field_cve=CVE-2021-30860government-resource, US government resource
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