CVE-2026-25278 Overview
CVE-2026-25278 is a memory corruption vulnerability in Qualcomm components caused by a race condition between memory allocation and data copying during Inter-Integrated Circuit (I2C) transfer request processing. The flaw is classified under [CWE-367] Time-of-Check Time-of-Use (TOCTOU) race condition. A local authenticated attacker with low privileges can trigger the race to corrupt kernel memory, leading to loss of confidentiality, integrity, and availability. The vulnerability requires no user interaction and affects the local attack surface exposed by the I2C driver interface.
Critical Impact
A successful race window exploitation corrupts kernel memory during I2C transfer handling, enabling privilege escalation or arbitrary code execution at the kernel level on affected Qualcomm platforms.
Affected Products
- Qualcomm components processing I2C transfer requests (specific chipsets and driver versions are enumerated in the Qualcomm Security Bulletin)
- Devices and platforms integrating the affected Qualcomm I2C driver stack
- Refer to the Qualcomm Security Bulletin September 2026 for the complete affected component list
Discovery Timeline
- 2026-09-17 - CVE-2026-25278 published to NVD
- 2026-09-17 - Last updated in NVD database
Technical Details for CVE-2026-25278
Vulnerability Analysis
The vulnerability resides in the code path that handles I2C transfer requests inside affected Qualcomm drivers. When a transfer request arrives, the driver allocates a memory buffer sized according to attacker-controllable request parameters. It then copies user-supplied data into that buffer in a separate step. Between the allocation decision and the copy operation, the request metadata can be modified from a concurrent thread. This creates a classic time-of-check to time-of-use window where the buffer size no longer matches the amount of data written, producing a heap out-of-bounds write.
Memory corruption at this layer is executed inside kernel context, so successful exploitation translates directly into kernel-level primitives such as adjacent object overwrite, function pointer hijack, or credential structure modification.
Root Cause
The root cause is the absence of atomic handling for I2C transfer parameters. The driver reads size and layout fields, allocates memory, and then re-reads the same fields during the copy operation without holding a lock or working from a validated kernel-side copy. A second thread modifying the shared request structure between these operations invalidates the size check performed at allocation time. This satisfies the [CWE-367] pattern of concurrent execution using a shared resource with improper synchronization.
Attack Vector
Exploitation requires local access with low privileges, typically an unprivileged process on the device that can open the I2C driver interface. The attacker submits I2C transfer requests from one thread while a second thread continuously mutates the shared request buffer. Winning the race causes the driver to allocate a smaller buffer than the data ultimately copied, or vice versa, corrupting adjacent kernel memory. The technical details for the exact syscall path and structure fields are documented in the Qualcomm Security Bulletin September 2026.
No public proof-of-concept code has been released, and no verified exploit examples are available for reproduction.
Detection Methods for CVE-2026-25278
Indicators of Compromise
- Unexpected kernel panics or reboots referencing I2C driver stack frames in the crash log
- Kernel oops entries with slab or heap corruption signatures traced to I2C transfer handlers
- Unprivileged processes repeatedly opening I2C device nodes and issuing high-frequency transfer ioctls from multiple threads
Detection Strategies
- Monitor kernel logs (dmesg, logcat) for KASAN or SLUB corruption reports referencing the I2C subsystem
- Instrument the I2C ioctl entry points with audit rules to flag concurrent access patterns from the same PID
- Correlate abnormal I2C driver crash telemetry with subsequent privilege changes or process anomalies on the same device
Monitoring Recommendations
- Enable kernel address sanitizer builds in test fleets to surface race-driven out-of-bounds writes early
- Ingest device kernel crash reports into a centralized data lake for pattern analysis across the fleet
- Track unprivileged processes that access /dev/i2c-* nodes and alert on unusual multi-threaded transfer workloads
How to Mitigate CVE-2026-25278
Immediate Actions Required
- Apply the Qualcomm security patch referenced in the September 2026 bulletin as soon as it is available through the OEM update channel
- Inventory devices using affected Qualcomm chipsets and prioritize patch deployment for high-value or multi-user endpoints
- Restrict access to I2C device nodes to trusted system components and remove permissions from unprivileged user contexts
Patch Information
Qualcomm has published remediation guidance in the Qualcomm Security Bulletin September 2026. Device manufacturers must integrate the vendor patch into their firmware or Android security patch level release and push it to end devices. The fix is expected to enforce serialized handling of I2C transfer parameters, ensuring that the buffer size used for allocation is the same value used during the data copy.
Workarounds
- Tighten SELinux or discretionary access control policies to block unprivileged domains from opening I2C character devices
- Disable optional userspace I2C interfaces on production devices where they are not required for functionality
- Reduce local attack surface by limiting installation of untrusted applications on affected devices until firmware updates arrive
Disclaimer: This content was generated using AI. While we strive for accuracy, please verify critical information with official sources.
