CVE-2026-64560 — posix-cpu-timers: Prevent UAF caused by non-leader exec() race

Affected: Linux, Siemens SIMATIC S7-1500 CPU 1518-4 PN/DP MFP, Siemens SIMATIC S7-1500 CPU 1518F-4 PN/DP MFP, Siemens SIPLUS S7-1500 CPU 1518-4 PN/DP MFP

In the Linux kernel, the following vulnerability has been resolved:

posix-cpu-timers: Prevent UAF caused by non-leader exec() race

Wongi and Jungwoo decoded and reported a non-leader exec() related race which can result in an UAF:

sys_timer_delete() exec() posix_cpu_timer_del() // Observes old leader p = pid_task(pid, pid_type); de_thread() switch_leader(); release_task(old_leader) __exit_signal(old_leader) sighand = lock(old_leader, sighand); posix_cpu_timers*_exit(); sighand = lock_task_sighand(p) unhash_task(old_leader); sh = lock(p, sighand) old_leader->sighand = NULL; unlock(sighand); (p->sighand == NULL) unlock(sh) return NULL;

// Returns without action if(!sighand) return 0; free_posix_timer();

This is "harmless" unless the deleted timer was armed and enqueued in p->signal because on exec() a TGID targeted timer is inherited.

As sys_timer_delete() freed the underlying posix timer object run_posix_cpu_timers() or any timerqueue related add/delete operations on other timers will access the freed object's timerqueue node, which results in an UAF.

There is a similar problem vs. posix_cpu_timer_set(). For regular posix timers it just transiently returns -ESRCH to user space, but for the use case in do_cpu_nanosleep() it's the same UAF just that the k_itimer is allocated on the stack.

Also posix_cpu_timer_rearm() fails to rearm the timer, which mean…

USN-8875-1 — linux, linux-aws, linux-aws-5.15, linux-aws-fips, linux-azure, linux-azure-5.15, linux-azure-fde-5.15, linux-azure-fips…

Affected: Ubuntu:Pro:20.04:LTS: linux-aws-5.15, Ubuntu:Pro:20.04:LTS: linux-azure-5.15, Ubuntu:Pro:20.04:LTS: linux-azure-fde-5.15, Ubuntu:Pro:20.04:LTS: linux-hwe-5.15, Ubuntu:Pro:20.04:LTS: linux-ibm-5.15, Ubuntu:Pro:20.04:LTS: linux-intel-iotg-5.15, Ubuntu:Pro:20.04:LTS: linux-lowlatency-hwe-5.15, Ubuntu:22.04:LTS: linux, Ubuntu:22.04:LTS: linux-aws, Ubuntu:22.04:LTS: linux-azure and 13 more

It was discovered that the i.MX clock driver in the Linux kernel did not properly handle certain memory allocation failure conditions, leading to a null pointer dereference vulnerability. A local attacker could possibly use this to cause a denial of service (system crash). (CVE-2022-3114)

Several security issues were discovered in the Linux kernel. An attacker could possibly use these to compromise the system. This update corrects flaws in the following subsystems: - User-space API (UAPI); - ARM32 architecture; - ARM64 architecture; - MIPS architecture; - PowerPC architecture; - RISC-V architecture; - User-Mode Linux (UML); - x86 architecture; - Block layer subsystem; - Cryptographic API; - ACPI drivers; - Android drivers; - Serial ATA and Parallel ATA drivers; - Drivers core; - DRBD Distributed Replicated Block Device drivers; - Rados block device (RBD) driver; - Bluetooth drivers; - Cdrom driver; - Character device driver; - Hardware random number generator core; - TPM device driver; - Data acquisition framework and drivers; - CPU frequency scaling framework; - Hardware crypto device drivers; - DAX dirext access to differentiated memory framework; - DMA engine subsystem; - FireWire subsystem; - Arm Firmware Framework for ARMv8-A(FFA); - ARM SCMI message protocol; - Intel Stratix 10 firmware drivers; - FPGA Framework; - GPIO subsystem; - GPU drivers; - HID subsystem; - Hardware monitoring drivers; - In…

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CVE-2026-64560 — posix-cpu-timers: Prevent UAF caused by non-leader exec() race

USN-8875-1 — linux, linux-aws, linux-aws-5.15, linux-aws-fips, linux-azure, linux-azure-5.15, linux-azure-fde-5.15, linux-azure-fips…