CVE-2026-64469: Linux Kernel Use-After-Free Vulnerability

CVE-2026-64469 Overview

CVE-2026-64469 is a use-after-free vulnerability in the Linux kernel's binder inter-process communication driver. The flaw resides in binder_thread_release(), which walks a thread's transaction stack when the thread exits. A parallel process termination can invoke binder_free_transaction() on the same transaction, releasing memory that binder_thread_release() continues to access. The race triggers a write to freed slab memory, confirmed by KASAN reports in the upstream fix commit. Local unprivileged users on affected kernels can trigger the condition through standard binderioctl() operations. The vulnerability affects kernel memory integrity and can lead to privilege escalation on Android and Linux systems that expose the binder driver.

Critical Impact
A local, low-privileged attacker can trigger a kernel use-after-free through concurrent binder transactions, corrupting kernel memory and enabling privilege escalation or denial of service.

Affected Products

Linux kernel versions containing the vulnerable binder_thread_release() and binder_free_transaction() locking pattern
Android platforms built on affected upstream Linux kernels using the binder IPC driver
Distributions shipping kernels prior to the fixes referenced by commits 114a116, 1f96f8c, 38e1a71, df1a17a, e63032d, ea02df4, ef5439b, and faa070c

Discovery Timeline

2026-07-25 - CVE-2026-64469 published to NVD
2026-07-27 - Last updated in NVD database

Technical Details for CVE-2026-64469

Vulnerability Analysis

The defect is a classic concurrency-induced use-after-free in the Linux binder driver. When a thread exits, binder_thread_release() iterates the thread's transaction stack to clear t->from and t->to_proc references pointing back to the exiting thread. The routine attempts to acquire t->to_proc->inner_lock before touching each transaction. However, a transaction may already have t->to_proc cleared by another path. In that case, no lock is taken, and the exiting thread continues to reference the transaction object without serialization.

In parallel, a dying peer process can reach binder_free_transaction() via binder_send_failed_reply() and binder_release_work(). That path calls kfree() on the same transaction. binder_thread_release() then writes into the freed slab object. KASAN reports the condition as slab-use-after-free in binder_thread_release+0x5d0/0x798, with an 8-byte write to a chunk freed roughly 23 seconds earlier during transaction cleanup.

Root Cause

The root cause is a violation of the documented locking rules for the @to_proc field of a binder transaction. binder_free_transaction() did not read t->to_proc while holding the transaction lock, so it could race with binder_thread_release() when the latter had already observed a NULL t->to_proc and skipped acquiring inner_lock. The two paths therefore lacked mutual exclusion over transaction lifetime.

Attack Vector

Exploitation requires local code execution with the ability to open /dev/binder and issue BINDER_WRITE_READioctl() calls. An attacker orchestrates two cooperating processes: one that owns a transaction and exits its thread, and another that terminates so that binder_release_work() frees the shared transaction. Winning the race produces a kernel-mode write into a freed slab object, which can be shaped into a controlled use-after-free primitive for privilege escalation. No user interaction and no elevated privileges are required beyond binder access.

No public proof-of-concept is referenced in the advisory. The upstream fix serializes access by reading t->to_proc under the transaction lock inside binder_free_transaction(), matching the documented locking rules and preventing the race.

Detection Methods for CVE-2026-64469

Indicators of Compromise

KASAN reports referencing slab-use-after-free in binder_thread_release in kernel logs or dmesg output
Unexpected kernel oops or panic stack traces containing binder_thread_release, binder_free_transaction, or binder_release_work
Processes repeatedly opening /dev/binder and issuing high volumes of concurrent BINDER_WRITE_READioctl() calls from unprivileged users

Detection Strategies

Enable KASAN on test and canary kernels to surface binder use-after-free conditions before production impact
Audit installed kernel package versions against the fixed commits listed in the upstream advisory
Correlate crash-dump telemetry with the binder_thread_release call path to identify exploitation attempts against unpatched hosts

Monitoring Recommendations

Ship kernel ring buffer and dmesg output to a centralized log pipeline for KASAN and oops keyword alerting
Monitor unprivileged process access to /dev/binder on servers and workloads that do not require Android IPC
Alert on unexpected kernel module loads or kernel version mismatches following patch deployment windows

How to Mitigate CVE-2026-64469

Immediate Actions Required

Apply the upstream Linux kernel patches referenced by commits 114a116, 1f96f8c, 38e1a71, df1a17a, e63032d, ea02df4, ef5439b, and faa070c
Prioritize patching on multi-tenant Linux hosts and Android devices where local users interact with the binder driver
Reboot systems after kernel package updates to ensure the fixed binder code path is loaded

Patch Information

The fix modifies binder_free_transaction() to read t->to_proc under the transaction lock. This serializes the transaction release path with binder_thread_release() and restores the documented locking contract for @to_proc. Distribution-specific backports are tracked in the upstream stable trees. See the Kernel Git Commit 38e1a71 and Kernel Git Commit faa070c references for the canonical fix and stable backports.

Workarounds

Restrict access to /dev/binder where the binder driver is not required, using device permissions or LSM policy
Unload or disable the binder kernel module on servers that do not host Android runtime or IPC workloads
Enforce process isolation and mandatory access controls (SELinux, AppArmor) to limit which unprivileged users can invoke binderioctl() operations

bash

# Verify running kernel version and confirm patch inclusion
uname -r

# Inspect whether the binder module is loaded
lsmod | grep binder

# Optionally restrict access on non-Android Linux hosts
chmod 600 /dev/binder