This issue was addressed with improved permissions checking

CVE-2026-28910 is an Archive Utility permission-checking flaw in macOS Tahoe 26.0 through 26.3 that Apple fixed in macOS Tahoe 26.4. Apple describes it as a malicious app being able to access arbitrary files, and the public Mysk research shows a practical chain that can read files from app containers, reach TCC-protected locations like ~/Desktop and ~/Documents, and tamper with third-party app bundles.

Apple's LOW / 3.3 rating is too charitable for the *impact* but too generous for the *reachability*. In real fleets this is not initial access: the attacker needs code execution as the user and a very specific drag-and-drop action, which is meaningful friction; but once that hurdle is cleared, the blast radius is far beyond a routine low-grade local info leak, so I upgrade it to MEDIUM.

Why this verdict

• Upgrade for impact: public research shows practical access to app containers, TCC-protected folders, and application bundles, which is much nastier than a routine low-grade local disclosure bug.
• Downgrade for attacker position: exploitation starts only after the attacker gets local code running as the user. That is not initial access; it is post-execution on a single Mac.
• Downgrade for user choreography: despite the vendor vector's UI:N, the published chain needs the victim to run a script and perform a very specific drag-and-drop. Each extra human step compounds failure rate in managed fleets.
• Downgrade for exposure population: the vulnerable set is limited to Tahoe 26.0-26.3, not all supported Apple operating systems or all macOS branches.
• No live-fire amplifier: there is no KEV listing and I found no credible active exploitation reporting, which removes the biggest reason to push this into HIGH.

Why not higher?

This is not remotely reachable, not wormable, and not one-click reliable. The attacker needs either a prior foothold or a successful user-execution phish, then a second tailored user action, so the real exposed population is far narrower than a network service bug or a drive-by browser exploit.

Why not lower?

Calling this LOW ignores what the public PoC actually does once it lands: broad endpoint data access and app tampering across trusted local boundaries. In a developer-heavy Mac fleet, users who normalize curl|bash install patterns make this chain practical enough that backlog-only treatment is too relaxed.

1. Block unsanctioned shell-bootstrap installs — Use MDM, application control, or EDR policy to curb curl|bash, sh -c "$(curl ...)", and similar bootstrap patterns on managed Macs. For a MEDIUM verdict there is no mitigation SLA; apply this in the normal hardening cycle, while still planning to patch affected hosts within the 365-day remediation window.
2. Hunt for Archive Utility preference tampering — Create detections for defaults write com.apple.archiveutility, suspicious access to com.apple.archiveutility.plist, noninteractive open -a "Archive Utility", and archive operations against app-container paths. There is no mitigation SLA for MEDIUM, so treat this as targeted detection engineering rather than an emergency rollout.
3. Constrain risky Terminal usage on user endpoints — Developer tooling exceptions aside, reduce who can run arbitrary shell installers and mount unsigned DMGs. This does not replace patching, but it cuts the exact social-engineering path the public PoC depends on; roll it out through normal endpoint control changes and remediate vulnerable Tahoe builds within 365 days.
4. Inventory Tahoe 26.0-26.3 in MDM — Make the problem measurable: identify Macs on the affected version range, then sort by user cohort, privilege, and data sensitivity. Since this is MEDIUM, there is no mitigation SLA — go straight to remediation planning and clear the affected population inside the 365-day patch window.

Run this on the target Mac itself from Terminal, locally or through your MDM/remote shell. Invoke it as bash check-cve-2026-28910.sh; it needs no admin privileges and reports VULNERABLE, PATCHED, or UNKNOWN based on the installed macOS version.

#!/bin/bash
# check-cve-2026-28910.sh
# Determine likely exposure to CVE-2026-28910 by macOS version.
# Affected according to NVD/Apple: macOS Tahoe 26.0 through 26.3
# Fixed: macOS Tahoe 26.4
# Exit codes: 0=PATCHED, 1=VULNERABLE, 2=UNKNOWN

set -u

ver_ge() {
  # returns 0 if $1 >= $2
  local IFS=.
  local i
  local -a va vb
  read -r -a va <<< "$1"
  read -r -a vb <<< "$2"
  local len=${#va[@]}
  if [ ${#vb[@]} -gt "$len" ]; then
    len=${#vb[@]}
  fi
  for ((i=0; i<len; i++)); do
    local a=${va[i]:-0}
    local b=${vb[i]:-0}
    if ((10#$a > 10#$b)); then
      return 0
    fi
    if ((10#$a < 10#$b)); then
      return 1
    fi
  done
  return 0
}

ver_lt() {
  # returns 0 if $1 < $2
  if ver_ge "$1" "$2"; then
    return 1
  else
    return 0
  fi
}

if [ "$(uname -s 2>/dev/null)" != "Darwin" ]; then
  echo "UNKNOWN - not running on macOS"
  exit 2
fi

if ! command -v sw_vers >/dev/null 2>&1; then
  echo "UNKNOWN - sw_vers not available"
  exit 2
fi

VER="$(sw_vers -productVersion 2>/dev/null)"
if [ -z "$VER" ]; then
  echo "UNKNOWN - unable to read macOS version"
  exit 2
fi

# Optional sanity check: Archive Utility should exist on macOS.
ARCHIVE_APP="/System/Library/CoreServices/Applications/Archive Utility.app"
if [ ! -d "$ARCHIVE_APP" ]; then
  echo "UNKNOWN - Archive Utility not found at expected path; macOS version is $VER"
  exit 2
fi

if ver_ge "$VER" "26.0" && ver_lt "$VER" "26.4"; then
  echo "VULNERABLE - macOS $VER is in the affected range for CVE-2026-28910"
  exit 1
fi

if ver_ge "$VER" "26.4"; then
  echo "PATCHED - macOS $VER includes the fix for CVE-2026-28910"
  exit 0
fi

# Versions below 26.0 are outside the published affected range.
echo "PATCHED - macOS $VER is outside the published affected range for CVE-2026-28910"
exit 0

Sources

1. Apple security advisory for macOS Tahoe 26.4
2. NVD record for CVE-2026-28910
3. Mysk technical write-up and PoC details
4. CISA Known Exploited Vulnerabilities Catalog
5. Tenable CVE page with EPSS data
6. Apple Developer: App Sandbox
7. Apple Developer: Protecting local app data using containers on macOS