CVE-2026-21107: Samsung Notes Buffer Overflow Vulnerability

CVE-2026-21107 Overview

CVE-2026-21107 is an out-of-bounds write vulnerability [CWE-787] in Samsung Notes. The flaw affects all versions of Samsung Notes prior to 4.4.45.5. A local attacker with low privileges can write outside the bounds of an allocated memory buffer. Successful exploitation can lead to memory corruption, application compromise, and potential impact to confidentiality on the device.

Samsung addressed the issue in its September 2026 mobile security maintenance release. The vulnerability requires local access and no user interaction, but does require the attacker to already hold some privileges on the target device.

Critical Impact
Local attackers can corrupt memory in Samsung Notes, enabling potential code execution in the application context and exposure of sensitive note data stored on the device.

Affected Products

Samsung Notes versions prior to 4.4.45.5
Samsung Galaxy devices running vulnerable Samsung Notes builds
Android installations with Samsung Notes as a preloaded or user-installed application

Discovery Timeline

2026-09-09 - CVE-2026-21107 published to the National Vulnerability Database (NVD)
2026-09-09 - Last updated in NVD database
September 2026 - Samsung publishes the fix in its Samsung Mobile Security Notification for September 2026

Technical Details for CVE-2026-21107

Vulnerability Analysis

The vulnerability is classified as an out-of-bounds write [CWE-787] in Samsung Notes. Out-of-bounds write conditions occur when an application writes data past the end, or before the beginning, of an intended buffer. This class of memory corruption frequently leads to heap or stack metadata corruption, adjacent object clobbering, and, when combined with attacker-controlled data, arbitrary code execution.

Samsung has not published detailed internal information about the affected code path. The advisory indicates the flaw is reachable by a local attacker with limited privileges and does not require user interaction. Because Samsung Notes handles user content including images, drawings, attachments, and structured note formats, the parsing of untrusted note data is a probable trigger surface.

The issue impacts confidentiality significantly, with lower impact to integrity and availability. This aligns with a memory corruption primitive that primarily leaks or manipulates in-process data rather than crashing the device outright.

Root Cause

The root cause is missing or incorrect bounds validation before a memory write operation in Samsung Notes. When the application processes a crafted input, it writes beyond the boundary of the destination buffer. Samsung has not disclosed the specific function or parsing routine responsible. Refer to the Samsung Mobile Security Notification for vendor-supplied details.

Attack Vector

Exploitation requires local access to a device running a vulnerable Samsung Notes build. The attacker must have at least low privileges, such as those granted to a standard installed Android application. A malicious app could deliver a crafted note file, share intent, or content payload to Samsung Notes to trigger the out-of-bounds write. No user interaction is required once the payload reaches the vulnerable code path.

Detailed exploitation code has not been publicly released. No public proof-of-concept is available at this time, and the vulnerability is not listed in the CISA Known Exploited Vulnerabilities catalog.

Detection Methods for CVE-2026-21107

Indicators of Compromise

Unexpected crashes or SIGSEGV faults attributed to the com.samsung.android.app.notes process in Android logs
Installation of untrusted third-party applications that request access to note content or send intents to Samsung Notes
Anomalous file writes or unusual note database modifications in Samsung Notes application storage

Detection Strategies

Inventory Samsung Notes versions across managed mobile fleets and flag any device running a build earlier than 4.4.45.5
Monitor mobile device management (MDM) telemetry for application crash reports involving Samsung Notes
Review sideloaded application installations on corporate-managed Samsung devices for suspicious permissions or intent filters targeting Samsung Notes

Monitoring Recommendations

Enable and centralize Android crash reporting for enterprise-managed Samsung devices to catch memory corruption symptoms early
Track Samsung Mobile Security Maintenance Release (SMR) bulletins and correlate patched versions against fleet inventory
Alert on note files or attachments originating from untrusted sources being opened in Samsung Notes

How to Mitigate CVE-2026-21107

Immediate Actions Required

Update Samsung Notes to version 4.4.45.5 or later through the Galaxy Store or Google Play Store
Apply the Samsung September 2026 security maintenance release on all affected Galaxy devices
Restrict installation of untrusted third-party applications on managed Samsung devices through MDM policies

Patch Information

Samsung fixed CVE-2026-21107 in Samsung Notes version 4.4.45.5. Details are available in the Samsung Mobile Security Notification for September 2026. Enterprise administrators should push the updated Samsung Notes package through their MDM solution or require users to update via the Galaxy Store.

Workarounds

Disable or uninstall Samsung Notes on devices where updating is not immediately possible, if the application is not business-critical
Prevent opening note files, attachments, or shared content from untrusted sources within Samsung Notes
Enforce Android application allowlisting through MDM to block installation of unverified applications that could deliver a crafted payload

bash

# Example: check Samsung Notes version via ADB on a managed device
adb shell dumpsys package com.samsung.android.app.notes | grep versionName