CVE-2026-58731 Overview
CVE-2026-58731 is an out-of-bounds read vulnerability affecting multiple functions in physmem_extmem_linux.c. The flaw stems from uninitialized data being accessed during memory operations, enabling local information disclosure. Exploitation requires no user interaction and no additional execution privileges. The vulnerability is documented in the Android Security Bulletin for September 2026 and is tracked under [CWE-125] (Out-of-bounds Read).
Critical Impact
A local attacker can read out-of-bounds memory to disclose sensitive information from the affected process without requiring elevated privileges or user interaction.
Affected Products
- Android platform components referencing physmem_extmem_linux.c
- Devices covered by the Android Security Bulletin September 2026
Discovery Timeline
- 2026-09-15 - CVE-2026-58731 published to the National Vulnerability Database (NVD)
- 2026-09-16 - Last updated in NVD database
Technical Details for CVE-2026-58731
Vulnerability Analysis
The vulnerability resides in multiple functions within physmem_extmem_linux.c, a component that handles physical and external memory operations on Linux-based Android systems. Affected code paths read from memory regions containing uninitialized data, allowing adjacent or residual memory contents to be exposed to the caller. Because the read occurs beyond the intended buffer boundary or before initialization completes, sensitive kernel or process memory can leak to a local attacker. The consequence is loss of confidentiality without impact to integrity or availability.
Root Cause
The root cause is uninitialized memory usage combined with insufficient bounds checking on read operations. When the affected functions return data structures to callers, portions of the buffer that were never explicitly initialized are copied along with valid data. This pattern maps directly to [CWE-125] Out-of-bounds Read and is a common source of information disclosure in kernel-adjacent memory management code.
Attack Vector
Exploitation requires local access to the affected device. An attacker with the ability to invoke the vulnerable functions, typically through a local application or process, can trigger the out-of-bounds read and receive uninitialized memory in the response. No user interaction is required and no additional privileges are needed beyond the ability to reach the affected code path. See the Android Security Bulletin September 2026 for component-level details.
Detection Methods for CVE-2026-58731
Indicators of Compromise
- Unexpected local processes repeatedly invoking memory management interfaces tied to physmem_extmem_linux.c
- Anomalous read patterns targeting physical or external memory allocation APIs from non-system applications
Detection Strategies
- Monitor system call telemetry for unusual invocation frequencies of memory allocation and mapping routines by unprivileged processes.
- Correlate installation of untrusted applications with subsequent access to low-level memory management interfaces.
- Apply behavioral analytics to flag processes that read memory buffers without corresponding writes or initialization patterns.
Monitoring Recommendations
- Enable mobile threat defense telemetry to capture application behavior on Android endpoints.
- Track patch level compliance against the September 2026 Android Security Bulletin across the managed device fleet.
- Log and review sideloaded application installations and permissions granted to non-Play Store applications.
How to Mitigate CVE-2026-58731
Immediate Actions Required
- Apply the September 2026 Android security patch level to all affected devices as soon as vendor updates are available.
- Inventory devices that cannot receive the patch and prioritize replacement or compensating controls.
- Restrict installation of untrusted local applications that could reach the vulnerable code path.
Patch Information
Google addressed CVE-2026-58731 in the September 2026 Android Security Bulletin. Device manufacturers ship the corresponding fix as part of the 2026-09-01 security patch level or later. Refer to the Android Security Bulletin September 2026 for component references and update guidance specific to Pixel and partner devices.
Workarounds
- No vendor-supplied workaround is documented; apply the security patch when available.
- Limit exposure by enforcing mobile device management (MDM) policies that block installation of unknown applications.
- Enroll high-risk devices in a mobile threat defense program to detect anomalous local behavior until patching completes.
Disclaimer: This content was generated using AI. While we strive for accuracy, please verify critical information with official sources.