CVE-2026-55294: HEVC Decoder Privilege Escalation Vulnerability

CVE-2026-55294 Overview

CVE-2026-55294 is a heap buffer overflow vulnerability in the ihevcd_get_tu_data_size function of ihevcd_utils.c, a component of the Android High Efficiency Video Coding (HEVC) decoder. The flaw enables an out-of-bounds write on the heap that can result in local privilege escalation. Exploitation requires no additional execution privileges and no user interaction. The vulnerability is tracked under [CWE-122: Heap-based Buffer Overflow] and is documented in the Android Security Bulletin September 2026.

Critical Impact
A local attacker with low privileges can trigger a heap buffer overflow in the HEVC decoder to escalate privileges on affected Android devices without user interaction.

Affected Products

Android platform components using the libhevcdec HEVC decoder library
Devices patched by the Android Security Bulletin September 2026
Android media framework processes invoking ihevcd_get_tu_data_size

Discovery Timeline

2026-09-08 - CVE CVE-2026-55294 published to NVD
2026-09-08 - Last updated in NVD database

Technical Details for CVE-2026-55294

Vulnerability Analysis

The vulnerability resides in the ihevcd_get_tu_data_size routine within ihevcd_utils.c, part of the Android HEVC video decoder implementation. During parsing of transform unit (TU) metadata from an HEVC bitstream, the function writes beyond the bounds of a heap-allocated buffer. Because the media decoder runs inside privileged Android processes, a successful overflow can corrupt adjacent heap structures used by the media stack. An attacker leveraging this corruption can elevate privileges from a low-privileged local context to a higher-privileged execution context. Exploitation does not require user interaction, which increases the risk when malicious media is auto-processed by system components.

Root Cause

The root cause is missing or insufficient bounds validation on transform unit size calculations before writing into a heap buffer. When a crafted HEVC stream provides parameters that inflate the computed TU data size, the writer proceeds past the allocated region, corrupting neighboring heap metadata or objects. This class of defect is categorized as [CWE-122: Heap-based Buffer Overflow].

Attack Vector

The attack vector is local. A malicious application already resident on the device, or a component that feeds attacker-controlled HEVC data to the decoder, can trigger the overflow. The attacker must have low privileges but does not need user interaction. Since the media decoder handles untrusted input by design, any local pathway that reaches ihevcd_get_tu_data_size with crafted TU parameters becomes viable.

No verified public proof-of-concept code is available. Refer to the Android Security Bulletin September 2026 for advisory-level technical details.

Detection Methods for CVE-2026-55294

Indicators of Compromise

Unexpected crashes or tombstones in Android media processes referencing libhevcdec or ihevcd_utils
Installation of applications that request media processing permissions and deliver malformed HEVC content
Anomalous privilege transitions originating from media framework processes

Detection Strategies

Monitor Android logcat and tombstone artifacts for SIGSEGV or heap corruption signatures inside HEVC decoding paths
Inspect installed applications for HEVC files with malformed TU parameters using media validation tooling
Correlate media process crashes with subsequent privileged process launches to identify escalation attempts

Monitoring Recommendations

Enable and centralize Android crash telemetry to surface repeated faults in the media stack
Track patch-level compliance across the fleet against the September 2026 Android Security Bulletin
Alert on mobile device management (MDM) reports showing devices below the required security patch level

How to Mitigate CVE-2026-55294

Immediate Actions Required

Apply the September 2026 Android security patch to all affected devices as soon as vendor updates are available
Restrict installation of untrusted applications that can supply media to system decoders
Enforce mobile device management policies requiring the September 2026 security patch level or later

Patch Information

The fix is delivered through the Android Security Bulletin September 2026. Device manufacturers integrate the patch into monthly over-the-air (OTA) updates. Confirm the device reports a security patch level of 2026-09-01 or later.

Workarounds

Disable or restrict apps that process untrusted HEVC content until patches are deployed
Use MDM policies to block sideloading and enforce Google Play Protect scanning
Segment high-risk devices that cannot receive timely OTA updates from sensitive corporate resources

bash

# Verify Android security patch level on a device via ADB
adb shell getprop ro.build.version.security_patch
# Expected output: 2026-09-01 or later