CVE-2026-84548

Executive Summary

CVE-2026-84548 is an integer overflow vulnerability (CWE-190) in Apple macOS that was addressed through improved input validation. When a user processes a maliciously crafted document, the flaw may lead to an out-of-bounds read, resulting in high impact to confidentiality (C:H) and availability (A:H) with a base CVSS score of 7.1. All macOS users on unpatched Sequoia 15.8, Tahoe 26.7, and Golden Gate 27 builds are potentially affected; exploitation requires local user interaction (UI:R) to open the crafted document.

Technical Analysis

The vulnerability class is an integer overflow (CWE-190) occurring during the parsing or handling of a document. Per the NVD description, Apple resolved the issue "with improved input validation," indicating that prior to patching, insufficient bounds verification allowed an arithmetic value to wrap or overflow. This condition subsequently enabled an out-of-bounds (OOB) read.

Mechanism summary (derived strictly from the provided description):

• A crafted document causes an integer value to overflow during processing.
• The overflow defeats a size or index calculation.
• The result is an out-of-bounds read — the process reads memory beyond an intended buffer boundary.

Attack surface: Local document processing on macOS. The CVSS vector AV:L/AC:L/PR:N/UI:R/S:U indicates the attack vector is Local, complexity is Low, no privileges are required, but a user must interact (open/process the malicious document). The scope is Unchanged, meaning the vulnerable component's exploit cannot cross a security boundary to affect other components — impact remains confined to the affected process context.

Code-level detail: The NVD entry does not name specific functions, classes, file paths, or parameters. No CNA title was provided. Therefore, code-level specifics (e.g., the exact parsing routine, the arithmetic operation subject to overflow, or the buffer structure read out of bounds) are not available in the source data and are not asserted here. The reliable, evidence-backed statement is: an integer overflow in document processing, fixed by improved input validation, yielding an OOB read.

The OOB read is a memory-safety defect that can leak adjacent process memory. In the confidentiality dimension this could expose sensitive data residing in the same address space; in availability, a malformed read can trigger a crash (denial of service) of the processing application.

Exploitation Scenarios

Important constraint: No public PoC, exploit code, or Nuclei template exists for CVE-2026-84548. The exploit chain below is inferred at the vulnerability-class level from the NVD description and CVSS vector. No specific function names, endpoints, or parameters are invented.

1. Reconnaissance / Target Identification. An attacker identifies macOS users as targets. This is a client-side, local vector; the attacker does not need network access to the vulnerable component. Delivery requires social engineering or a delivery channel that gets the victim to open a document (e.g., email attachment, shared file, download).

2. Triggering the Flaw Class. The attacker crafts a document designed to induce an integer overflow during parsing. When the victim opens or processes the document, the arithmetic overflow corrupts a size/index computation, steering the parser into an out-of-bounds read. Because the attack requires user interaction (UI:R), the attacker must convince the target to open the file; no special privileges are needed (PR:N) and the attack has low complexity (AC:L).

3. Payload / Execution Method (class-level). The payload is the maliciously crafted document itself. The exploit primitive is the OOB read generated by the integer overflow. No specific execution technique (e.g., ROP, heap grooming, specific syscall) can be asserted from the available description.

4. Post-Exploitation Impact. Successful triggering yields an out-of-bounds read (information exposure, C:H) and probable process crash (availability, A:H). Given Scope:Unchanged and no integrity impact (I:N), the observable outcomes are memory disclosure and denial of service within the affected process, not a guaranteed full system compromise. An attacker may combine the leaked memory with other primitives, but no such chained exploit is documented for this CVE.

Impact Assessment

• Confidentiality (C:H): High — the OOB read may leak sensitive in-process memory.
• Integrity (I:N): None — the description and vector indicate no write primitive.
• Availability (A:H): High — malformed reads can crash the processing application.
• Base Score: 7.1 (High), vector CVSS:3.1/AV:L/AC:L/PR:N/UI:R/S:U/C:H/I:N/A:H.
• EPSS: 0.00168 (~6.5th percentile) — low near-term exploitation likelihood.
• CISA KEV: NO — no confirmed exploitation in the wild.
• Blast radius: Localized to the user session that opens the crafted document (Scope:Unchanged). Enterprise impact centers on endpoint users handling untrusted documents; a crash-oriented availability impact can disrupt productivity, while memory disclosure poses a data-exfiltration risk if chained.

Detection Guidance

Sigma Rule

title: Potential macOS Integer Overflow Document Processing (CVE-2026-84548) - Crash/OOB Read
id: 8f3c2a91-1d47-4e88-9b21-7c6e5a4d0b13
status: experimental
description: Detects abnormal termination of macOS document-based applications that may indicate exploitation of an integer overflow leading to an out-of-bounds read.
references:
  - https://nvd.nist.gov/vuln/detail/CVE-2026-84548
author: valtersit.com
date: 2026-01-01
logsource:
  product: macos
  category: process_creation
detection:
  selection:
    Image|endswith:
      - '/Preview'
      - '/TextEdit'
      - '/QuickLook'
    CommandLine|contains:
      - '.pdf'
      - '.rtf'
      - '.doc'
  crash_indicator:
    EventType: 'crash'
  condition: selection or crash_indicator
falsepositives:
  - Legitimate malformed documents or normal application crashes
level: low

YARA Rule

rule CVE_2026_84548_Integer_Overflow_Document
{
    meta:
        description = "Heuristic detection of crafted documents targeting macOS integer overflow / OOB read (CVE-2026-84548)"
        author = "valtersit.com"
        reference = "https://nvd.nist.gov/vuln/detail/CVE-2026-84548"
        date = "2026-01-01"
    strings:
        $pdf = "%PDF-"
        $rtf = "{\\rtf"
        $mz  = { 4D 5A }
    condition:
        (uint16(0) == 0x504B or $pdf at 0 or $rtf at 0)
        and filesize < 50MB
        and (
            #pdf > 1 or // embedded/crafted PDF structures
            #rtf > 1
        )
}

(Note: No vendor-provided byte signatures exist for this CVE; the above is a structural heuristic and must be tuned to your environment.)

Suricata IDS Rule

alert tcp any any -> any any (msg:"CVE-2026-84548 macOS Document Integer Overflow Delivery Attempt"; flow:established,to_client; file_data; content:"%PDF-"; content:"/Obj"; nocase; threshold:type limit, track by_src, count 1, seconds 60; classtype:attempted-user; sid:90084548; rev:1; metadata:reference cve,CVE-2026-84548;)

(Detects delivery of PDF-style document objects to a client; true exploitation is local and not directly observable on the wire.)

Elastic Detection

process where event.type == "start" and process.executable != null and
  process.name in ("Preview", "TextEdit", "QuickLook", "mdimport") and
  process.args like~ ("*.pdf", "*.rtf", "*.doc*")

Correlate with subsequent crash events via event.action == "crash".

Splunk SPL Query

index=macos sourcetype=osquery OR sourcetype=macos_unified_logs
("Preview" OR "TextEdit" OR "QuickLook" OR "mdworker")
| search ("crash" OR "EXC_BAD_ACCESS" OR "out-of-bounds" OR "KERN_INVALID_ADDRESS")
| stats count min(_time) as first_seen max(_time) as last_seen by host, process_name, file_path
| where count > 0
| sort - count

Wazuh OSSEC Rule

<group name="macos,cve-2026-84548,">
  <rule id="100548" level="6">
    <decoded_as>json</decoded_as>
    <field name="event.type">crash</field>
    <field name="process.name">Preview|TextEdit|QuickLook|mdworker</field>
    <description>CVE-2026-84548: macOS document parser crash - possible integer overflow/OOB read exploitation</description>
    <mitre>
      <id>T1203</id>
    </mitre>
  </rule>
</group>

Mitigation & Patch Guidance

Patch confidence: 2/4 (CLAIMED) — a single source (NVD) claims a patch; this has not been independently confirmed. Verify against the official Apple security advisory before treating remediation as complete.

1) Immediate mitigations

• Restrict opening of untrusted documents; apply mail/web download and macro-blocking controls.
• Use OS-level hardening (Gatekeeper, XProtect, sandboxed viewers) to limit parser reach.
• Monitor endpoint logs for repeated document-parser crashes as a signal of malicious documents.

2) Patch / upgrade steps

• Upgrade to macOS Golden Gate 27, macOS Sequoia 15.8, or macOS Tahoe 26.7, per the NVD-fixed versions.
• Confirm the actual version string and build number in Apple menu > About This Mac against Apple's published advisory.
• Enforce patch management for all managed Macs; prioritize users who routinely open external documents.

3) Long-term hardening

• Keep document-viewing applications updated and minimize the number of parsers exposed to untrusted input.
• Deploy the detection rules above and enable end-of-process crash telemetry.
• Track the CVE at NVD and Apple for an authoritative advisory and any change in EPSS/KEV status.

References

1. NVD — CVE-2026-84548: https://nvd.nist.gov/vuln/detail/CVE-2026-84548
2. CWE-190 Integer Overflow or Wraparound: https://cwe.mitre.org/data/definitions/190.html
3. FIRST EPSS (CVE-2026-84548): https://api.first.org/data/v1/epss?cve=CVE-2026-84548
4. CISA Known Exploited Vulnerabilities Catalog (status: NOT listed): https://www.cisa.gov/known-exploited-vulnerabilities-catalog
5. Apple Security Releases (verify vendor advisory for exact fixed versions): https://support.apple.com/en-us/HT201222

Exploit-in-the-wild / threat actor evidence: None. CVE-2026-84548 is NOT in CISA KEV, no public PoC and no exploit code are known, and EPSS is 0.00168. The report above contains no confirmed active campaign data.