CVE-2026-43788

Executive Summary

CVE-2026-43788 is an integer overflow (CWE-190) in Apple macOS that was addressed through improved input validation. Per the NVD description, processing a maliciously crafted file may result in a denial-of-service condition or potentially disclose memory contents. The CVSS v3.1 base score is 6.6 (Medium), with an Attack Vector of Local (AV:L), Attack Complexity Low (AC:L), Privileges Required Low (PR:L), and User Interaction Required (UI:R) — indicating that an attacker must already have local access and convince a user to open a crafted file.

Technical Analysis

The vulnerability class is an integer overflow (CWE-190). Per the NVD description, the defect resides in input validation logic that fails to properly bound a numeric value derived from file contents. When a maliciously crafted file is processed, the improperly validated integer value overflows a buffer or size calculation, which the description states may lead to a denial-of-service or the potential disclosure of memory contents.

The impact profile — Confidentiality High and Availability High, with Integrity None — is consistent with an out-of-bounds read or allocation-size miscalculation. The description specifically names two outcomes: a denial-of-service (Availability High) and "potentially disclose memory contents" (Confidentiality High). It does NOT describe code execution or memory corruption leading to control-flow hijack, and no Integrity impact is scored, which aligns with a read-side overflow rather than a write-wild primitive.

The attack surface is local and requires user interaction (AV:L / UI:R). The trigger is "processing a maliciously crafted file." The NVD description does not name the affected subsystem, file format parser, or a specific binary. No function names, file paths, class names, or parameters are provided in the CNA Title (empty) or the NVD Description, so no code-level detail can be responsibly asserted here. The specific component — whether a media format, image parser, archive handler, font engine, or document processor — is not disclosed in the provided data.

Because the description affirmatively states "was addressed with improved input validation," the pre-patch behavior is a validation gap on a numeric field. The post-patch behavior adds bounds checking to that value. This is a classic integer overflow remediation pattern: length, count, or offset fields read from an untrusted file were multiplied or summed without overflow guards, and the fix constrains the input.

No exploit code, no PoC, and no Nuclei template are publicly available per the provided intelligence. EPSS is 0.00142 (3.9th percentile), indicating a very low predicted probability of exploitation in the wild in the near term. CVE-2026-43788 is NOT listed in the CISA KEV catalog.

Exploitation Scenarios

No public PoC is available; the attack chain below is inferred strictly from the vulnerability class (integer overflow) and the NVD description ("processing a maliciously crafted file may lead to a denial-of-service or potentially disclose memory contents").

1. Reconnaissance / target identification. An adversary with existing local access on a macOS Golden Gate 27 host identifies a file-processing entry point — a document viewer, preview handler, or import operation that opens untrusted files. No network-facing service is implied; the vector is local with user interaction. The attacker determines which file types the victim routinely opens.

2. Crafting the trigger file. The attacker constructs a file whose numeric length, count, or offset field is set to a value that overflows when the vulnerable parser computes a size or index from it. Because the NVD description states the fix is "improved input validation," the pre-patch code accepted the oversized value without a bounds check.

3. Delivery and user interaction. The crafted file is delivered via email attachment, download, shared volume, or removable media. The UI:R and PR:L metrics require that the attacker has a local foothold or can place the file where a user will open it, and that the user performs the opening action. The overflow is triggered during parsing.

4. Post-exploitation impact. Per NVD, the result is either a denial-of-service (crash of the parsing process or system disruption) or potential disclosure of memory contents (out-of-bounds read exposing data from adjacent memory). No code execution, persistence, or privilege escalation is described in the provided data; claims of RCE would be unsupported speculation.

Impact Assessment

CVSS v3.1 base score: 6.6 (Medium). Subscore interpretation from the provided vector:

• Attack Vector Local (AV:L): exploitation requires local access to the target host.
• Attack Complexity Low (AC:L): no special conditions beyond the crafted file.
• Privileges Required Low (PR:L): the attacker needs a low-privileged foothold or ability to stage a file.
• User Interaction Required (UI:R): a victim must open the malicious file.
• Scope Unchanged (S:U): impact is confined to the vulnerable component.
• Confidentiality High (C:H): potential memory disclosure.
• Integrity None (I:N): no data modification described.
• Availability High (A:H): denial-of-service is explicitly stated.

Business impact centers on availability disruption of the affected file-processing workflow and potential exposure of sensitive in-memory data (credentials, keys, decrypted documents) if memory disclosure is achieved. Blast radius is bounded by the local-attack and user-interaction requirements — this is not a wormable or remotely unauthenticated issue. EPSS of 0.00142 and absence from CISA KEV indicate low near-term exploitation likelihood, but local file-parser bugs are attractive to attackers who already hold a foothold and want to escalate impact or exfiltrate secrets.

Detection Guidance

Sigma Rule

title: Suspicious File Processing Crash or Memory Disclosure on macOS (CVE-2026-43788)
id: 8f3c1a20-4b7e-4c9a-9d21-43788cve0001
status: experimental
description: Detects abnormal termination of macOS file-processing processes consistent with an integer overflow trigger via crafted file
references:
  - https://nvd.nist.gov/vuln/detail/CVE-2026-43788
author: valtersit.com
date: 2026/01/01
logsource:
  product: macos
  category: process_creation
detection:
  selection_crash:
    Image|endswith:
      - '/QuickLook'
      - '/Preview'
      - '/mdworker'
    ExitStatus: 11
  condition: selection_crash
falsepositives:
  - Legitimate crashes from corrupt files
level: low
tags:
  - attack.t1203
  - cve.2026-43788

YARA Rule

rule CVE_2026_43788_IntegerOverflow_File_Trigger
{
    meta:
        description = "Heuristic detection of crafted files abusing integer overflow (CVE-2026-43788)"
        author = "valtersit.com"
        reference = "https://nvd.nist.gov/vuln/detail/CVE-2026-43788"
        date = "2026-01-01"
        severity = "medium"
    strings:
        $mz = { 4D 5A }
        $pdf = "%PDF-"
        $zip = { 50 4B 03 04 }
        $ff = { FF FF FF FF }
    condition:
        (uint32(0) == 0x46464952 or $mz at 0 or $pdf at 0 or $zip at 0) and
        filesize < 20MB and
        $ff
}

Suricata IDS Rule

alert smb any any -> any any (msg:"CVE-2026-43788 Potential Crafted File Transfer to macOS Host"; flow:established,to_server; content:"|FF FF FF FF|"; depth:8; filestore; sid:4378801; rev:1; metadata:created_at 2026_01_01, cve CVE_2026_43788;)

Elastic Detection

process where process.name in ("QuickLook", "Preview", "mdworker") and
 process.exit_code == 11 and event.action == "end"

Splunk SPL Query

index=macos sourcetype=macos:syslog
(process_name=QuickLook OR process_name=Preview OR process_name=mdworker)
(signal=SEGV OR exit_status=11 OR "Segmentation fault")
| stats count by host, process_name, file_name
| where count > 3

Note: This detection is heuristic. The NVD description does not specify a subsystem, so no process name can be asserted as authoritative; adjust process_name to the actual affected parser once Apple publishes advisories.

Wazuh OSSEC Rule

<group name="macos,cve-2026-43788,">
  <rule id="437880" level="6">
    <decoded_as>json</decoded_as>
    <field name="process">QuickLook|Preview|mdworker</field>
    <match>Segmentation fault|exit code 11</match>
    <description>CVE-2026-43788: macOS file parser crash - possible integer overflow DoS</description>
    <mitre>
      <id>T1203</id>
    </mitre>
  </rule>
</group>

Mitigation & Patch Guidance

Patch confidence: 2/4 (CLAIMED). NVD states the issue is "fixed in macOS Golden Gate 27," but no independent vendor advisory, patch ID, or build delta is available to confirm the boundary between vulnerable and patched builds. Treat the fix as unverified.

1. Immediate mitigations:

• Apply the macOS Golden Gate 27 update that NVD references, once its build identifier is confirmed against Apple's security release notes.
• Until patch confirmation, restrict opening of untrusted files on Golden Gate 27 hosts; block high-risk file types at email gateways and web proxies.
• Enforce least privilege so a local attacker cannot stage files into high-value user contexts.

2. Patch/upgrade steps:

• Verify the current macOS build number and compare against Apple's published patched build for Golden Gate 27.
• Deploy the update via MDM; validate post-patch build string.
• Because patch confidence is only 2/4, independently confirm remediation (e.g., re-test a crafted sample once a public PoC or Apple advisory is available).

3. Long-term hardening:

• Keep macOS patched within a defined SLA for local-vector, medium-severity issues.
• Enable endpoint crash telemetry (see Detection Guidance) to catch parser crashes.
• Reduce user interaction risk through file-type allowlisting and application sandboxing.

References

• NVD — CVE-2026-43788: https://nvd.nist.gov/vuln/detail/CVE-2026-43788
• CWE-190 Integer Overflow or Wraparound: https://cwe.mitre.org/data/definitions/190.html
• Apple Security Releases (macOS): https://support.apple.com/en-us/HT201222
• CISA KEV Catalog (CVE-2026-43788 not listed): https://www.cisa.gov/known-exploited-vulnerabilities-catalog
• FIRST EPSS (score 0.00142): https://www.first.org/epss

Threat actor campaigns / exploit-in-the-wild: None reported. No PoC, no Nuclei template, no exploit code, and no CISA KEV listing per provided intelligence. EPSS 0.00142 (3.9th percentile) indicates low predicted exploitation activity.