CVE-2025-31246: Apple macOS Buffer Overflow Vulnerability

CVE-2025-31246 Overview

CVE-2025-31246 is a memory corruption vulnerability in Apple macOS affecting the Apple Filing Protocol (AFP) client. Connecting to a malicious AFP server can corrupt kernel memory, enabling potential code execution at the kernel level. Apple addressed the issue with improved memory handling in macOS Sequoia 15.5 and macOS Sonoma 14.7.6. The flaw is classified under [CWE-119] (Improper Restriction of Operations within the Bounds of a Memory Buffer) and impacts confidentiality, integrity, and availability when a user is induced to mount an attacker-controlled AFP share.

Critical Impact
A network-reachable AFP server controlled by an attacker can corrupt macOS kernel memory, leading to potential arbitrary code execution in the kernel context.

Affected Products

Apple macOS Sonoma prior to 14.7.6
Apple macOS Sequoia prior to 15.5
Systems mounting AFP shares from untrusted servers

Discovery Timeline

2025-05-12 - CVE-2025-31246 published to NVD
2025-05-12 - Apple releases security patches in macOS Sequoia 15.5 and macOS Sonoma 14.7.6
2025-11-03 - Last updated in NVD database

Technical Details for CVE-2025-31246

Vulnerability Analysis

The vulnerability resides in the macOS AFP client implementation, which handles communication with AFP file servers. When the client parses responses from a malicious AFP server, improper memory handling leads to kernel memory corruption. Apple's advisory describes the fix as "improved memory handling," consistent with [CWE-119] memory boundary issues such as out-of-bounds writes or heap corruption inside kernel-mode networking code.

Because AFP processing occurs in kernel context on macOS, successful exploitation can compromise the entire operating system. The attacker requires low privileges on the victim system, typically the ability to trigger a mount operation to an attacker-controlled host. No user interaction beyond initiating the connection is required once the attacker can influence the AFP target.

Root Cause

The root cause is improper validation or bounds checking when processing untrusted data received from a remote AFP server. Crafted protocol responses cause the macOS kernel AFP client to write or read outside intended buffer boundaries, corrupting adjacent kernel structures. Apple resolved the defect by tightening memory handling within the affected code path.

Attack Vector

The attack vector is network-based. An attacker hosts a malicious AFP server and convinces the victim, or an automated process, to connect using afp:// URLs, mount_afp, or Finder share browsing. Once the macOS client initiates the AFP session, the malicious server returns crafted protocol messages that trigger the kernel memory corruption.

The vulnerability can be exploited in scenarios such as phishing links pointing to AFP shares, malicious Bonjour advertisements on local networks, or compromised legitimate file servers. No verified public proof-of-concept or exploit code is available at the time of writing. The flaw is not listed in the CISA Known Exploited Vulnerabilities catalog.

See the Apple Security Advisory #122716 and Apple Security Advisory #122717 for vendor details.

Detection Methods for CVE-2025-31246

Indicators of Compromise

Unexpected outbound TCP connections to port 548 (AFP) destined for untrusted external hosts.
Kernel panics or panic.ips reports referencing AFP client modules (afpfs) on macOS endpoints.
mount_afp process invocations referencing unfamiliar server hostnames or IP addresses.
Bonjour or mDNS announcements advertising rogue AFP services on local network segments.

Detection Strategies

Inspect unified logs with log show --predicate 'subsystem contains "afp"' for abnormal protocol errors preceding system instability.
Monitor endpoint telemetry for kernel extension faults and reboots correlated with AFP mount events.
Alert on connections to TCP/548 leaving the corporate perimeter, since AFP traffic should rarely traverse the internet.

Monitoring Recommendations

Centralize macOS unified logs and crash reports for retrospective hunting on AFP-related panics.
Track macOS build versions in asset inventory to confirm patch coverage for 14.7.6 and 15.5.
Baseline expected AFP file servers and alert on connections to any host outside the allowlist.

How to Mitigate CVE-2025-31246

Immediate Actions Required

Update all macOS endpoints to macOS Sequoia 15.5 or macOS Sonoma 14.7.6 without delay.
Block outbound TCP port 548 at the perimeter firewall unless AFP is required for business operations.
Instruct users to avoid mounting AFP shares from unknown or untrusted sources.
Identify and decommission legacy AFP servers in favor of SMB where possible.

Patch Information

Apple released fixes in macOS Sequoia 15.5 and macOS Sonoma 14.7.6 on May 12, 2025. The patches apply improved memory handling within the AFP client code path. Refer to Apple Security Advisory #122716 and Apple Security Advisory #122717 for the complete list of addressed issues and supported hardware.

Workarounds

Restrict AFP client usage by blocking TCP/548 egress at network boundaries until patches are deployed.
Disable automatic mounting of AFP shares advertised through Bonjour on untrusted networks.
Enforce mobile device management (MDM) policies that prevent users from connecting to arbitrary afp:// URLs.

bash

# Verify patched macOS build on endpoints
sw_vers -productVersion

# Block outbound AFP at the host firewall using pf
echo "block out proto tcp to any port 548" | sudo pfctl -ef -