CVE-2026-21072 Overview
CVE-2026-21072 is an improper input validation vulnerability in the VC1 codec implementation within libsavsvc.so on Samsung mobile devices. The flaw allows a local attacker to trigger an out-of-bounds memory write when processing malformed VC1 video data. Samsung addressed the issue in the SMR Aug-2026 Release 1 security maintenance update. The vulnerability is tracked under [CWE-20: Improper Input Validation] and requires local access to exploit. Successful exploitation can corrupt adjacent memory, leading to application instability or potential code execution within the affected media service context.
Critical Impact
Local attackers can write out-of-bounds memory in the VC1 codec, corrupting process memory in the media service and potentially enabling code execution in that context.
Affected Products
- Samsung mobile devices running firmware prior to SMR Aug-2026 Release 1
- libsavsvc.so shared library implementing the VC1 codec
- Applications and services that invoke the VC1 decoding path on affected Samsung builds
Discovery Timeline
- 2026-08-10 - CVE-2026-21072 published to the National Vulnerability Database (NVD)
- 2026-08-10 - Samsung SMR Aug-2026 Release 1 addresses the vulnerability
- 2026-08-10 - Last updated in NVD database
Technical Details for CVE-2026-21072
Vulnerability Analysis
The vulnerability resides in the VC1 codec code path inside libsavsvc.so, a Samsung media service library. The library fails to validate specific fields within VC1 bitstream input before using those values to compute buffer offsets or lengths. When a crafted VC1 stream is parsed, the codec writes outside the bounds of an allocated buffer.
Out-of-bounds writes in media codecs commonly result in heap metadata corruption or overwrites of adjacent object data. Because the flaw is reachable through local media processing, an attacker who can deliver VC1 content to the codec, for example through an installed application or a crafted media file opened by a privileged service, can trigger the corruption.
The EPSS probability for CVE-2026-21072 is low, reflecting the local attack vector and codec-specific reachability. Exploitation still requires primitives to convert the write into control flow or data-only impact within the media service.
Root Cause
The root cause is missing or insufficient bounds checking on attacker-controlled fields in the VC1 parser. Trusted length or index values derived from the input stream are used directly in memory write operations without validation against the destination buffer size.
Attack Vector
The attack vector is local. An attacker delivers a malformed VC1 stream to the codec through an application, content provider, or local media file. No user interaction and no privileges are required beyond the ability to submit media to the decoder on the device.
No public proof-of-concept is available for CVE-2026-21072. See the Samsung Mobile Security Update for vendor-published details on the fix.
Detection Methods for CVE-2026-21072
Indicators of Compromise
- Repeated crashes or SIGSEGV signals in processes that load libsavsvc.so during VC1 media playback or parsing
- Tombstone entries in /data/tombstones/ referencing the VC1 codec functions within libsavsvc.so
- Unexpected termination of media services immediately after opening a specific VC1-encoded file
Detection Strategies
- Monitor Android crash logs and logcat output for native crashes attributed to libsavsvc.so and VC1 decoding routines
- Correlate crash events with the application or content source that supplied the offending media file
- Track installed application inventory for apps that programmatically pass VC1 streams to system decoders
Monitoring Recommendations
- Alert on a rising rate of native media service crashes across a fleet of Samsung devices
- Retain tombstone and dropbox artifacts from managed devices to support post-incident triage
- Verify the applied security patch level (ro.build.version.security_patch) reflects SMR Aug-2026 Release 1 or later
How to Mitigate CVE-2026-21072
Immediate Actions Required
- Install Samsung SMR Aug-2026 Release 1 or a later security maintenance release on all affected devices
- Confirm the security patch level on managed devices through mobile device management (MDM) tooling
- Restrict installation of untrusted applications that can supply arbitrary media content to system codecs
Patch Information
Samsung addressed CVE-2026-21072 in the SMR Aug-2026 Release 1 update. Details are published in the Samsung Mobile Security Update advisory for August 2026. Apply the update through the device System Update mechanism or push it via enterprise MDM.
Workarounds
- Avoid opening VC1-encoded media from untrusted sources until the security patch is applied
- Enforce application allow-listing on managed devices to reduce exposure to malicious media-handling apps
- Use MDM policies to require the SMR Aug-2026 Release 1 patch level for access to corporate resources
Disclaimer: This content was generated using AI. While we strive for accuracy, please verify critical information with official sources.
