CVE-2026-21124 in Samsung
Summary
by MITRE • 10/12/2026
Improper input validation in getting cover image in libsimba.heifdec.media.samsung.so prior to SMR Oct-2026 Release 1 allows local attackers to potentially execute arbitrary code.
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Analysis
by VulDB Data Team • 10/12/2026
The vulnerability identified involves a critical flaw within the HEIF decoding library, specifically located in the file libsimba.heifdec.media.samsung.so, which is part of Samsung's multimedia processing stack prior to the SMR October 2026 Release 1 update. This component is responsible for handling High Efficiency Image File format data, a standard increasingly used in modern mobile photography due to its superior compression ratios compared to legacy formats like JPEG. The core technical deficiency lies in improper input validation during the extraction and processing of cover images embedded within HEIF files. When an application requests or parses these metadata structures, the library fails to adequately verify the integrity, bounds, or type safety of the incoming data streams before passing them to lower-level memory management routines. This lack of rigorous sanitization creates a classic buffer overflow condition where crafted input can exceed allocated memory boundaries, allowing for arbitrary code execution on the device.
From an operational perspective, this vulnerability poses a severe risk because it resides in a system-level library that is often accessible by multiple applications and services within the Android operating environment. Although the initial description specifies local attackers, the nature of multimedia processing means that such vulnerabilities can be triggered through various vectors including maliciously crafted images received via messaging apps, downloaded from websites, or embedded in emails. An attacker who successfully exploits this flaw could achieve arbitrary code execution with the privileges of the process invoking the HEIF decoder. In many mobile architectures, if the decoding occurs within a privileged system service rather than an isolated sandboxed application context, the resulting compromise can lead to full device takeover, enabling data exfiltration, persistence mechanisms, and lateral movement across connected services or devices on the same network segment.
This flaw aligns with Common Weakness Enumeration (CWE) category CWE-20 Improper Input Validation, as the root cause is the failure to restrict or verify inputs before processing. Furthermore, it maps directly to MITRE ATT&CK technique T1203 Exploitation for Client Execution, where attackers leverage trusted software components to execute malicious payloads on target systems without requiring direct user interaction beyond opening a file. The absence of proper bounds checking and type validation in the cover image retrieval logic exemplifies how complex binary formats can be weaponized when developers assume input integrity or rely on outdated parsing libraries that lack modern security hardening features such as Address Space Layout Randomization (ASLR) compatibility checks or stack canisters integration at the library level.
Mitigation strategies must focus primarily on applying the vendor-provided software update scheduled for October 2026, which addresses this specific input validation gap within libsimba.heifdec.media.samsung.so. Until such patches are deployed across all affected devices, defensive measures should include restricting permissions for applications that handle untrusted image files to ensure they operate in restricted sandboxed environments with minimal system-level access. Additionally, implementing runtime application self-protection (RASP) mechanisms or memory corruption detection tools can help identify and block exploitation attempts of buffer overflow vulnerabilities in real-time. Developers integrating HEIF processing capabilities should also enforce strict input sanitization protocols, validating all metadata fields against expected schemas and enforcing hard limits on data sizes before invoking native decoding functions to prevent similar issues in custom implementations.