CVE-2026-56997 Overview
CVE-2026-56997 is an out-of-bounds write vulnerability in the Av1DecodeFrameTag function of vp9hwd_headers.cc. The flaw stems from a missing bounds check when parsing AV1 frame tag data. An attacker can trigger the condition remotely without user interaction, leading to escalation of privilege on affected Android devices. The issue is tracked under [CWE-787] (Out-of-bounds Write) and disclosed in the Android Security Bulletin for September 2026.
Critical Impact
Successful exploitation permits remote privilege escalation without additional execution privileges or user interaction, potentially compromising confidentiality, integrity, and availability of affected devices.
Affected Products
- Android devices incorporating the vulnerable vp9hwd_headers.cc AV1 decoder component
- Pixel devices covered by the September 2026 Android Security Bulletin
- Downstream Android distributions shipping the unpatched media codec library
Discovery Timeline
- 2026-09-15 - CVE-2026-56997 published to the National Vulnerability Database (NVD)
- 2026-09-16 - Last updated in NVD database
Technical Details for CVE-2026-56997
Vulnerability Analysis
The vulnerability resides in Av1DecodeFrameTag, a routine within vp9hwd_headers.cc responsible for decoding AV1 frame tag fields. The function processes attacker-influenced data without validating that the destination buffer can accommodate the write. When a crafted AV1 stream is parsed, execution reaches a write operation that exceeds the intended buffer boundary. This corrupts adjacent memory structures inside the media decoding process. Because Android media services run with elevated privileges relative to typical application sandboxes, a controlled overwrite can be leveraged to escalate privileges. The Android Security Bulletin classifies the issue as a remote escalation of privilege that requires no user interaction. Full technical context is available in the Android Security Bulletin September 2026.
Root Cause
The root cause is a missing bounds check inside Av1DecodeFrameTag. The decoder trusts length or index values derived from the untrusted AV1 bitstream and writes past the end of an internal buffer. This maps to [CWE-787] (Out-of-bounds Write).
Attack Vector
An attacker delivers a malformed AV1 media asset to a vulnerable component, for example through a messaging application, browser rendering pipeline, or media service that parses AV1 headers. Parsing the crafted frame tag triggers the out-of-bounds write inside the media process, enabling privilege escalation without user interaction.
No verified proof-of-concept code is available. Refer to the vendor advisory for authoritative technical details.
Detection Methods for CVE-2026-56997
Indicators of Compromise
- Unexpected crashes or SIGSEGV signals in Android media codec processes handling AV1 content
- Tombstone or logcat entries referencing Av1DecodeFrameTag or vp9hwd_headers
- Anomalous privilege transitions originating from media decoder processes shortly after AV1 media parsing
Detection Strategies
- Monitor Android crash telemetry for repeated faults in the AV1 decoding path across managed devices
- Inspect inbound media assets in messaging and browsing workflows for malformed AV1 frame tag structures
- Correlate media service crashes with subsequent process launches that request elevated capabilities
Monitoring Recommendations
- Enroll Android endpoints in a mobile threat defense solution that reports OS patch level and crash telemetry
- Track deployment status of the September 2026 Android Security Bulletin patch level across the fleet
- Alert on devices that remain below the fixed patch level after the vendor remediation window
How to Mitigate CVE-2026-56997
Immediate Actions Required
- Apply the September 2026 Android security patch level to all affected devices as soon as the OEM release is available
- Prioritize patching for devices that regularly render untrusted media from messaging, email, or web sources
- Restrict installation of applications from untrusted sources that may deliver malicious AV1 media
Patch Information
Google addressed CVE-2026-56997 in the September 2026 Android Security Bulletin. Device owners should install the update that reports the corresponding security patch level. See the Android Security Bulletin September 2026 for the authoritative list of fixed builds and Pixel updates.
Workarounds
- Disable auto-download of media attachments in messaging clients to reduce automatic parsing of untrusted AV1 content
- Avoid opening AV1 media from unknown senders until the security patch is applied
- Enforce mobile device management policies that require the September 2026 or later Android security patch level for network access
No vendor-approved configuration workaround is published. Patching remains the required remediation.
Disclaimer: This content was generated using AI. While we strive for accuracy, please verify critical information with official sources.
