CVE-2026-21068 Overview
CVE-2026-21068 is a stack-based buffer overflow in libril_sem.so, a Radio Interface Layer (RIL) library shipped in Samsung mobile devices. The flaw exists in versions prior to the Samsung Maintenance Release (SMR) Aug-2026 Release 1. A privileged local attacker can trigger the overflow to execute arbitrary code within the context of the affected process. The weakness is classified under CWE-121: Stack-based Buffer Overflow.
Critical Impact
Successful exploitation grants arbitrary code execution on the device, compromising confidentiality, integrity, and availability of the affected mobile platform.
Affected Products
- Samsung mobile devices running firmware prior to SMR Aug-2026 Release 1
- The libril_sem.so shared library component
- Samsung Radio Interface Layer subsystem
Discovery Timeline
- 2026-08-10 - CVE-2026-21068 published to NVD
- 2026-08-11 - Last updated in NVD database
- August 2026 - Samsung releases SMR Aug-2026 Release 1 addressing the vulnerability
Technical Details for CVE-2026-21068
Vulnerability Analysis
The vulnerability resides in libril_sem.so, a native library within Samsung's Radio Interface Layer that mediates communication between the Android telephony framework and the baseband modem. A stack-based buffer overflow [CWE-121] occurs when the library writes attacker-influenced data past the bounds of a fixed-size stack buffer. This corrupts adjacent stack memory, including saved return addresses and function pointers. An attacker with elevated local privileges can craft inputs that overwrite control-flow data. Once control flow is hijacked, the attacker executes arbitrary code within the RIL process context.
Root Cause
The root cause is missing or insufficient bounds checking during data copy operations into a stack-allocated buffer inside libril_sem.so. The library trusts the length or contents of caller-supplied data without validating it against the destination buffer size. Samsung has not published low-level technical details beyond the advisory reference.
Attack Vector
Exploitation requires local access to the device and elevated privileges. An attacker must first obtain a privileged execution context, typically a system-level process able to interact with the RIL interface. From that context, the attacker sends malformed data to libril_sem.so to trigger the overflow. No user interaction is required. The scope is limited to the vulnerable component; no cross-component escalation is described in the advisory.
No public proof-of-concept code is available for this vulnerability. Refer to the Samsung Security Update August 2026 advisory for vendor-provided details.
Detection Methods for CVE-2026-21068
Indicators of Compromise
- Unexpected crashes or SIGSEGV signals originating from processes linked against libril_sem.so
- Anomalous native code execution or memory regions marked executable within RIL-related processes
- Telephony service restarts or modem communication failures without a corresponding radio event
Detection Strategies
- Monitor Android tombstone files and logcat output for stack corruption traces referencing libril_sem.so
- Inspect installed firmware build fingerprints to identify devices running versions prior to SMR Aug-2026 Release 1
- Correlate privileged process behavior against baseline telephony stack activity to surface anomalous RIL interactions
Monitoring Recommendations
- Enroll devices in a mobile threat defense solution that ingests crash telemetry and firmware version data
- Alert on privileged local processes performing unexpected ioctl or IPC calls against RIL endpoints
- Track SMR patch level compliance across the mobile fleet and flag devices lagging behind the August 2026 baseline
How to Mitigate CVE-2026-21068
Immediate Actions Required
- Apply the Samsung SMR Aug-2026 Release 1 update to all affected devices
- Inventory the mobile fleet to identify devices running firmware predating the August 2026 SMR
- Restrict installation of untrusted applications that could obtain the privileged context required for exploitation
Patch Information
Samsung addressed CVE-2026-21068 in the SMR Aug-2026 Release 1 firmware update. Details are available in the Samsung Security Update August 2026 bulletin. Devices must receive the vendor or carrier over-the-air update to remediate the vulnerability.
Workarounds
- No vendor-supplied workaround is documented; patching remains the only complete remediation
- Enforce mobile device management policies that block sideloading and restrict privileged application installation until patches are applied
- Isolate high-risk or non-updatable devices from sensitive networks and data
Refer to the Samsung Security Update August 2026 advisory for firmware distribution status by device model.
Disclaimer: This content was generated using AI. While we strive for accuracy, please verify critical information with official sources.
