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CVE-2026-20971 is a high-severity use-after-free vulnerability discovered within Samsung’s KNOX security framework, specifically in the interaction between two kernel subsystems: PROCA (a proprietary process authenticator) and FIVE (the kernel integrity subsystem). The flaw resides in the `procfs` handlers under /proc/pid/integrity/, which access a `task_integrity` object without proper reference management in a fully preemptive kernel. When a process changes state—such as through forking or calling execve()—the old integrity object is released via task_integrity_put(old_tint), and a new one takes its place. This handoff should be atomic, but Android’s preemptive kernel allows an attacker to exploit the race window. One thread can read a pointer to the integrity object, get suspended by the scheduler, and later resume execution to use memory that has already been freed. Specifically, `proc_integrity_value_read()` resumes and calls `task_integrity_user_read()` with a pointer to freed memory. While the race window is extremely small—consisting of just a couple of opcodes—an attacker can manipulate scheduling to gain control. Samsung’s Kernel Control Flow Integrity (KCFI) mitigates arbitrary function calls, but researchers found a path by loading a non-ELF file, which removes a refcount blocker, allowing reallocation of freed memory in a controlled manner. This vulnerability affects Galaxy devices from the S9 through S25, including A-series models, across Android versions 13, 14, 15, and 16. Samsung patched the issue in the January 2026 Security Maintenance Release (SMR).
DailyCVE Form:
Platform: Samsung Galaxy (Android 13-16)
Version: SMR Jan-2026 Release 1
Vulnerability: Use-After-Free (Kernel)
Severity: High (CVSS 7.8)
date: January 2026
Prediction: Already Patched (Jan 2026)
What Undercode Say:
Check current security patch level on Samsung device
adb shell getprop ro.build.version.security_patch
Expected output for patched device:
2026-01-01 or later
Check KNOX version information
adb shell getprop ro.knox.version
Monitor /proc/pid/integrity/ access attempts (requires root)
adb shell su -c "logcat | grep -i integrity"
Check if device is running vulnerable SMR version (before Jan 2026)
adb shell getprop ro.build.fingerprint | grep -E "SMR([A-Z][a-z]{2}-2025|...)"
Exploit: (Educational Purposes!)
The exploitation leverages the race condition in PROCA/FIVE interaction. An untrusted local app triggers the vulnerability by:
1. Opening `/proc/pid/integrity/` for a target process and initiating a read operation on the `task_integrity` object.
2. Simultaneously forcing the target process to execute execve(), which frees the original `task_integrity` struct via task_integrity_put(old_tint).
3. Manipulating the scheduler to suspend the reading thread precisely within the race window.
4. Upon resumption, the thread calls `task_integrity_user_read()` on the freed memory, triggering the use-after-free.
5. Reallocating the freed memory with attacker-controlled data by loading a non-ELF file, bypassing KCFI restrictions.
6. Achieving kernel memory corruption primitives, including memory leaks for KASLR bypass and constrained writes.
Protection:
- Update Immediately: Install the Samsung January 2026 Security Maintenance Release (SMR Jan-2026 Release 1) or later.
- Verify Patch Level: Navigate to Settings → About Phone → Software Information → Security patch level. Ensure the date is 2026-01-01 or later.
- Application Awareness: Avoid installing untrusted applications from third-party sources, as the vulnerability can be triggered from any untrusted app.
- Device Replacement: For devices no longer receiving security updates, consider upgrading to a newer model.
Impact:
Successful exploitation allows a local attacker to trigger kernel memory corruption, potentially leading to complete device takeover. Attackers can obtain multiple memory corruption primitives, including memory leaks that aid in bypassing KASLR (Kernel Address Space Layout Randomization). Although KCFI blocks arbitrary function calls, other powerful primitives exist, enabling privilege escalation and deeper control over the device kernel. The flaw existed for approximately eight years, affecting millions of Galaxy devices from the S9 through S25 across multiple Android versions. Given that mobile endpoints are always on and often trusted, a compromised device can serve as a launch point for attacks against enterprise environments.
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Sources:
Reported By: nvd.nist.gov
Extra Source Hub:
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