CVE-2026-19809
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Kernel Stack Memory Disclosure in Zephyr RTOS Charger Subsystem
Vulnerability report for CVE-2026-19809, including description, CVSS score, EPSS score, affected products, exploitability, helpful resources, and attack-flow context.
Publication date: 2026-11-12
Last updated on: 2026-11-12
Assigner: Zephyr Project
Description
Description
The user-mode system call verifier z_vrfy_charger_get_prop() in drivers/charger/charger_handlers.c declares an uninitialized union charger_propval k_val on the kernel (privileged) stack, passes it to the charger driver back end via z_impl_charger_get_prop(), and then copies the full sizeof(union charger_propval) back into the calling user thread's buffer with k_usermode_to_copy(). That discloses kernel stack contents on two paths:
On error. The copy-out ignores the driver's return code. In-tree back ends return an error without writing through the value pointer for properties they do not implement: charger_gpio_get_prop() returns -ENOTSUP unconditionally, and bq24190_get_prop() has a default: return -ENOTSUP; arm that never touches val. The whole union is then stack residue.
On success. A back end writes only the one union member the requested property selects (for example sbs_charger.c writes the one-byte val->present for CHARGER_PROP_PRESENT and returns 0), yet the handler still copies the whole union, so every byte beyond that member is uninitialized.
The handler is compiled only when CONFIG_USERSPACE=y and is reachable by any user-mode thread that has been granted access to a charger device object. K_SYSCALL_DRIVER_CHARGER() validates only the device object and its API pointer, not the property identifier, so an unprivileged thread can choose prop freely: an unimplemented property forces the error path, a narrow one the success path, and the call can be repeated at will.
Each call discloses up to the size of the union (12 bytes on a 32-bit target, 16 bytes on 64-bit targets where the function-pointer members widen it) of supervisor-stack memory. The bytes are residue of earlier kernel-side frames on the thread's privileged stack and can contain kernel object addresses and saved return addresses, which an unprivileged thread cannot otherwise observe and which help defeat address-layout assumptions when exploiting a separate memory-safety defect. There is no integrity or availability impact.
Two commits fix it, and both are needed. 5054384e983c skips the copy-out when the back end reports an error. c31cac727d02 zeroes the union before the driver call, so the bytes copied out on success are driver-written data or zeros. A tree carrying only the first still leaks on every successful call.
CVSS Scores
EPSS Scores
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Meta Information
Affected Vendors & Products
| Vendor | Product | Version / Range |
|---|---|---|
| zephyrproject | zephyr | From 3.5.0 (inc) to 4.3.2 (exc) |
| zephyrproject | zephyr | From 4.4.0 (inc) to 4.5.0 (exc) |
Helpful Resources
Exploitability
CWE
KEV
| CWE ID | Description |
|---|---|
| CWE-908 | The product uses or accesses a resource that has not been initialized. |
| CWE-252 | The product does not check the return value from a method or function, which can prevent it from detecting unexpected states and conditions. |
