CVE-2025-62818: Samsung Exynos Buffer Overflow Vulnerability

CVE-2025-62818 Overview

An out-of-bounds write vulnerability has been discovered in Samsung Exynos mobile processors, wearable processors, and modems. The vulnerability occurs due to a mismatch between the TP-UDHI (User Data Header Indicator) and UDL (User Data Length) values when processing SMS TP-UD (Transfer Protocol - User Data) packets. This flaw allows remote attackers to potentially execute arbitrary code or cause system instability by sending specially crafted SMS messages to affected devices.

Critical Impact

This vulnerability enables remote code execution via malicious SMS messages without any user interaction, potentially allowing complete device compromise through the cellular baseband processor.

Affected Products

• Samsung Exynos Mobile Processors: 980, 990, 850, 1080, 2100, 1280, 2200, 1330, 1380, 1480, 2400, 1580, 2500
• Samsung Exynos Wearable Processors: 9110, W920, W930, W1000
• Samsung Exynos Modems: 5123, 5300, 5400

Discovery Timeline

• 2026-04-07 - CVE-2025-62818 published to NVD
• 2026-04-09 - Last updated in NVD database

Technical Details for CVE-2025-62818

Vulnerability Analysis

This vulnerability is classified as CWE-787 (Out-of-Bounds Write), affecting the SMS message processing functionality within Samsung Exynos baseband firmware. The flaw resides in how the processor handles incoming SMS messages, specifically in the parsing logic for TP-UD packets.

When an SMS message is received, the baseband processor parses the message structure including the TP-UDHI flag and UDL field. The TP-UDHI indicates whether a User Data Header is present, while the UDL specifies the length of the user data. A mismatch between these values can cause the processor to write data beyond allocated buffer boundaries.

The network-accessible nature of this vulnerability is particularly concerning as it requires no user interaction—an attacker only needs the target's phone number to potentially exploit this flaw. The baseband processor operates with high privileges, making successful exploitation especially dangerous.

Root Cause

The root cause is improper validation of the relationship between the TP-UDHI flag and the UDL value in SMS TP-UD packet processing. When the TP-UDHI indicates a User Data Header is present, the UDL should account for this header's length. However, the vulnerable code fails to properly validate this relationship, allowing an attacker to specify inconsistent values that result in the processor writing data past the intended buffer boundaries.

Attack Vector

The attack can be executed remotely over the cellular network. An attacker crafts a malicious SMS message with manipulated TP-UDHI and UDL values that create a mismatch in the expected data length calculations. When the vulnerable Exynos processor receives and processes this SMS, the inconsistent length values cause the firmware to perform an out-of-bounds write operation.

The exploitation flow involves:

1. Attacker identifies a device using a vulnerable Exynos processor
2. Attacker sends a specially crafted SMS with mismatched TP-UDHI and UDL values
3. The baseband processor receives and parses the malicious SMS
4. The length mismatch causes data to be written outside allocated memory bounds
5. Depending on the memory layout, this could lead to code execution or denial of service

Due to the sensitive nature of baseband vulnerabilities, specific exploitation details are not provided. Refer to the Samsung CVE-2025-62818 Advisory for technical details.

Detection Methods for CVE-2025-62818

Indicators of Compromise

• Unexpected device reboots or baseband processor crashes when receiving SMS messages
• Unusual baseband processor behavior or error logs in system diagnostics
• Anomalous cellular network traffic patterns indicating exploitation attempts

Detection Strategies

• Monitor device logs for baseband processor exceptions or crashes related to SMS processing
• Implement network-level SMS filtering at the carrier level to detect malformed SMS packets
• Deploy endpoint detection solutions capable of monitoring baseband processor behavior

Monitoring Recommendations

• Enable verbose logging on affected devices where possible to capture baseband events
• Coordinate with mobile carriers to implement SMS message inspection for malformed TP-UD packets
• Use SentinelOne mobile threat defense to detect anomalous device behavior indicative of baseband exploitation

How to Mitigate CVE-2025-62818

Immediate Actions Required

• Check device firmware versions and identify affected Exynos processors in your environment
• Apply Samsung security updates as soon as they become available for affected devices
• Consider temporarily disabling SMS functionality on critical devices until patches are applied
• Monitor Samsung's security bulletins for patch availability

Patch Information

Samsung has acknowledged this vulnerability and is releasing security patches through their standard update channels. Device manufacturers using affected Exynos processors should obtain firmware updates from Samsung. End users should install the latest system updates provided by their device manufacturer.

For detailed patch information, consult the Samsung Product Security Updates page and the specific Samsung CVE-2025-62818 Advisory.

Workarounds

• Enable airplane mode on affected devices when not actively using cellular connectivity
• Use alternative communication methods (Wi-Fi calling, messaging apps) until patches are available
• For enterprise environments, consider network-level SMS filtering where technically feasible
• Implement mobile device management (MDM) policies to ensure rapid patch deployment

# Verify device processor model on Android devices
adb shell cat /proc/cpuinfo | grep -i "Hardware\|model"

# Check current firmware version
adb shell getprop ro.build.display.id

# Monitor baseband logs for anomalies
adb logcat -b radio | grep -i "sms\|TP-UD\|exception"