CVE-2026-21043 Overview
CVE-2026-21043 is a path traversal vulnerability in the Samsung Wallpaper service on Samsung Mobile devices. The flaw exists in versions prior to Security Maintenance Release (SMR) Jul-2026 Release 1. Local attackers with elevated privileges can traverse directory structures to access files that should remain isolated from the Wallpaper service context. Successful exploitation grants access to files with system_server privileges, exposing sensitive Android system data.
Critical Impact
Local privileged attackers can read arbitrary files accessible to system_server, resulting in confidentiality loss across protected Android system resources.
Affected Products
- Samsung Mobile devices running Android with the Wallpaper service
- Firmware versions prior to SMR Jul-2026 Release 1
- Samsung devices receiving the July 2026 Security Maintenance Release
Discovery Timeline
- 2026-07-10 - CVE-2026-21043 published to NVD
- 2026-07-11 - Last updated in NVD database
Technical Details for CVE-2026-21043
Vulnerability Analysis
The vulnerability is a path traversal weakness in the Samsung Wallpaper service. The service processes file paths without sufficient canonicalization, allowing input containing traversal sequences such as ../ to escape the intended directory. An attacker with local access and elevated privileges submits a crafted path to the Wallpaper service. The service then resolves and opens the target file using its own system_server privilege context.
Because the Wallpaper service runs within system_server, files accessed through the traversal are read at that privilege level. This bypasses Android's application sandboxing for the requested resources. Confidentiality is directly impacted, while integrity and availability remain unaffected by this specific flaw. Exploitation requires local access and high privileges, limiting the attack to actors that already possess a foothold on the device.
Root Cause
The root cause is improper limitation of a pathname to a restricted directory in the Wallpaper service. Input validation fails to reject or normalize relative path segments before the service opens the file. This aligns with the Path Traversal weakness class [CWE-22].
Attack Vector
The attack vector is local. An attacker leverages an existing high-privilege context on the device to invoke the Wallpaper service with a manipulated file path. No user interaction is required. The service returns file contents or file handles that the attacker would not normally be authorized to access. Samsung has published details in the Samsung Mobile Security Update advisory for July 2026.
Detection Methods for CVE-2026-21043
Indicators of Compromise
- Wallpaper service requests containing path traversal sequences such as ../, encoded variants like %2e%2e%2f, or absolute paths pointing outside expected wallpaper directories
- Unexpected file access events under /data/system/, /data/misc/, or other privileged locations attributed to the Wallpaper service process
- Anomalous binder IPC calls to the Wallpaper service originating from privileged local processes
Detection Strategies
- Monitor Android system logs (logcat) for Wallpaper service errors, exceptions, or unusual file open operations referencing paths outside the wallpaper storage directory
- Correlate SELinux audit denials involving the system_server domain accessing atypical file contexts
- Track installation and behavior of privileged applications that interact with the Wallpaper service outside of documented APIs
Monitoring Recommendations
- Enroll Samsung mobile devices in a mobile threat defense solution that reports firmware patch level and flags devices below SMR Jul-2026 Release 1
- Alert on devices that remain unpatched beyond the organization's mobile update SLA
- Review privileged process telemetry from managed devices for unexpected file reads by system_server
How to Mitigate CVE-2026-21043
Immediate Actions Required
- Apply SMR Jul-2026 Release 1 or later to all affected Samsung Mobile devices through the standard OTA update channel
- Inventory Samsung devices in the fleet and confirm their reported security patch level meets or exceeds July 2026
- Restrict installation of applications that request elevated privileges on managed Samsung devices until patched
Patch Information
Samsung addressed CVE-2026-21043 in the July 2026 Security Maintenance Release (SMR Jul-2026 Release 1). Patch availability varies by device model and carrier. Refer to the Samsung Mobile Security Update bulletin for the list of impacted models and rollout timing.
Workarounds
- No official workaround has been published by Samsung; installing the SMR Jul-2026 Release 1 update is the supported remediation
- Enforce mobile device management (MDM) policies that block sideloading of untrusted applications to reduce the risk of a local privileged foothold
- Require full-disk encryption and strong screen-lock policies to limit physical access scenarios that could lead to local exploitation
# Verify Samsung device security patch level via ADB
adb shell getprop ro.build.version.security_patch
# Expected value on remediated devices: 2026-07-01 or later
Disclaimer: This content was generated using AI. While we strive for accuracy, please verify critical information with official sources.
