CVE-2026-121996
A length validation flaw in gdbserver's agent-expression parser allows an unauthenticated remote attacker to read uninitialized heap memory
CVSS
8.2
Alto
EPSS
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KEV
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Exploit Today
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0-100
Publicado: 5 nov 2026 · Última mod.: 5 nov 2026 · CWE-822
Sin historial EPSS suficiente todavía.
A length validation flaw in gdbserver's agent-expression parser allows an unauthenticated remote attacker to read uninitialized heap memory from the gdbserver process and cause a denial of service. Disclosed heap content includes addresses suitable for defeating ASLR in further exploitation.
CVECVSSEPSSKEVRExplotTítuloVis.
CVE-2026-1137809.3 CRÍ—
——0ESF-IDF is the Espressif Internet of Things (IOT) Development Framework. From 5.5.5 until 5.5.6, 6.0.4, and 6.1.1, the esp_tee trap entry in esp_tee_vectors_plic.S and esp_tee_vectors_clic.S saves a caller-controlled register frame through the REE-supplied stack pointer before switching to the trusted TEE stack or validating the pointer. A local unprivileged REE application can direct this machine-mode write into TEE-exclusive memory on ESP32-C5, ESP32-C6, ESP32-C61, and ESP32-H2 devices, breaking the REE/TEE isolation boundary and potentially corrupting TEE control-flow data for code execution, denial of service, or system crashes. Both secure-service ecall and interrupt entry paths contain the vulnerable ordering. This issue is fixed in version 5.5.6 and is scheduled to be fixed in versions 6.0.4 and 6.1.1.2hCVE-2026-870417.8 ALT1.5%
——0The RTIO submission-queue verifier rtio_vrfy_sqe() in subsys/rtio/rtio_syscalls.c (subsys/rtio/rtio_handlers.c before v4.3.0) accumulated the results of K_SYSCALL_MEMORY() into its valid_sqe flag with &=. That macro returns nonzero on failure (it is built on K_SYSCALL_VERIFY_MSG(), which yields !(expr)), so every buffer permission check contributed the opposite of its result. A submission whose tx.buf, rx.buf or txrx.tx_buf/txrx.rx_buf pointer was not accessible to the calling thread was accepted, while a legitimate, thread-owned buffer caused the calling thread to be killed with a kernel oops.
The verifier runs on behalf of the rtio_sqe_copy_in_get_handles() system call (also reached through the inline rtio_sqe_copy_in() wrapper), so it is driven directly by untrusted user-mode input on any image built with CONFIG_USERSPACE. A user thread that has been granted an RTIO context and an rtio_iodev object — the intended usage of RTIO userspace support, established via rtio_access_grant() — can submit an SQE whose buffer pointer and length name arbitrary kernel memory; the object check on sqe->iodev is unaffected and still passes, and the crafted SQE is forwarded to the bus driver unchanged.
Downstream consumers dereference the pointer with supervisor privilege. The generic I2C and I3C RTIO fallback handlers (drivers/i2c/i2c_rtio_default.c, drivers/i3c/i3c_rtio_default.c) copy sqe.rx.buf/sqe.tx.buf into struct i2c_msg and call i2c_transfer(), and the vendor SPI/I2C RTIO drivers behave equivalently. An RTIO_OP_RX submission therefore has peripheral data written into kernel memory of the attacker's choosing (arbitrary kernel write), an RTIO_OP_TX submission clocks kernel memory out over the bus (kernel memory disclosure), and a pointer to unmapped memory faults the kernel. This is a full escape from the user-mode isolation boundary that CONFIG_USERSPACE exists to enforce.
The defect was masked for years because the in-tree user-mode RTIO tests only exercise RTIO_OP_NOP and mempool-backed reads, neither of which reaches the affected checks. The fix negates each K_SYSCALL_MEMORY() result and additionally validates the TXRX transmit buffer read-only, matching the SPI, I2C and I3C handlers.2dCVE-2026-165118.8 ALT6.8%
——2Two RTIO syscall verifiers, in subsys/rtio/rtio_syscalls.c (subsys/rtio/rtio_handlers.c before v4.3.0), did not validate user-supplied pointers before the kernel wrote through them.
z_vrfy_rtio_sqe_cancel() performed no validation at all. It passed the caller's struct rtio_sqe pointer straight to z_impl_rtio_sqe_cancel(), which converts it with CONTAINER_OF to a struct rtio_iodev_sqe, ORs RTIO_SQE_CANCELED (BIT(3)) into its 16-bit flags field in supervisor mode, then loads its next pointer and repeats until that pointer is NULL. The syscall takes no RTIO context argument, so it needs no object grant: any user-mode thread on a CONFIG_USERSPACE build can set that bit in a 16-bit word at an address of its choosing in kernel memory, and the kernel continues the write along whatever pointer chain it finds at the corresponding offset. Setting chosen bits in kernel data structures, such as object permission or thread state fields, can be used to escalate privilege from user mode.
z_vrfy_rtio_sqe_copy_in_get_handles() validated its RTIO context and the input SQE array, but only NULL-checked the handle out-parameter before writing a kernel SQE pointer through it, with no K_SYSCALL_MEMORY_WRITE check. A user thread that holds a granted RTIO context can therefore make the kernel store a pointer value at an arbitrary address.
The fixes validate the handle out-parameter as writable, bound the cancel handle to real submission-pool storage, and require permission on the RTIO context that owns the matching pool. Without that last check a bounded handle still let any user thread cancel submissions belonging to other contexts, silently aborting their I/O. Systems built without CONFIG_USERSPACE or without CONFIG_RTIO are unaffected.2dCVE-2026-115653—3.8%
——1In Eclipse ThreadX versions 6.0.1 through 6.5.2.202603, the PendSV handler of the Cortex-M module ports saves a preempted user-mode module thread's registers in privileged mode at addresses taken from the thread's stack pointer, without checking that pointer against the thread's stack. A user-mode, memory-protected module can thereby write up to nine words, eight of its choosing, or 25 with floating-point state, into memory immediately below any region it may write, and read back what is stored there.3dCVE-2026-88781—1.4%
——0Untrusted Pointer Dereference in ASUS certain motherboards firmware allows a kernel-level privileges user can supply an arbitrary memory address via an I/O command, leading to subsequent system information being tampered with or causing a system crash.
Refer to the 'Security Update for Multiple ASUS Motherboards' section on the ASUS Security Advisory for more information.2dCVE-2026-196767.8 ALT9.9%
——3The user-mode verifier for the peci_transfer() system call, z_vrfy_peci_transfer() in drivers/peci/peci_handlers.c, checked only the device object permission and copied the caller-supplied struct peci_msg with k_usermode_from_copy(). That copy validates the outer structure only; the buf pointers and len values inside the embedded struct peci_buf members tx_buffer and rx_buffer remained fully caller-controlled and were passed unchecked to the driver.
Every in-tree PECI driver dereferences those pointers in supervisor mode: peci_npcx_transfer() in drivers/peci/peci_npcx.c and peci_it8xxx2_transfer() in drivers/peci/peci_ite_it8xxx2.c copy hardware bytes into rx_buffer.buf[i] and read command bytes out of tx_buffer.buf[i], and peci_xec_read()/peci_xec_write() in drivers/peci/peci_mchp_xec.c do the same with no bound on rx_buffer.len at all. A user-mode thread that has been granted the PECI device object — the normal way an application exposes a device under CONFIG_USERSPACE — could therefore point rx_buffer.buf at kernel data structures and have the driver write hardware-supplied bytes there, or point tx_buffer.buf at kernel memory and have its contents pushed onto the PECI/eSPI out-of-band bus.
The impact is a full user-mode-to-kernel escape: an arbitrary kernel write primitive (integrity and, through it, code execution at supervisor privilege), an arbitrary kernel read disclosed to a PECI bus observer, and a trivially reachable supervisor-mode fault if an unmapped address is supplied. Exploitation requires CONFIG_USERSPACE=y, one of the PECI drivers enabled (CONFIG_PECI_NPCX, CONFIG_PECI_XEC or CONFIG_PECI_ITE_IT8XXX2), and local code execution in a user-mode thread holding the PECI device.
The fix adds K_SYSCALL_MEMORY_READ() and K_SYSCALL_MEMORY_WRITE() checks over the two embedded buffers, with a size_add_overflow() guard on the frame-check-sequence byte accounted for in the RX length.2d