Description
i2s_esp32_trigger_check() in drivers/i2s/i2s_esp32.c validates the requested direction only for I2S_DIR_BOTH. The I2S_DIR_RX and I2S_DIR_TX branches read dev_cfg->rx.data->configured / dev_cfg->tx.data->configured without first checking the stream pointers. The device instantiation macro I2S_ESP32_STREAM_INIT() sets both .conf and .data to NULL for a direction the devicetree does not describe, so on an instance that wires only one direction — the normal shape for audio output or a worldsemi,ws2812-i2s LED strip — the other direction dereferences a NULL pointer instead of returning an error.

i2s_trigger() is a Zephyr syscall, and z_vrfy_i2s_trigger() in drivers/i2s/i2s_handlers.c validates only the device object and the presence of the trigger API pointer; the dir argument is passed to the driver unvalidated. On a build with CONFIG_USERSPACE enabled, a user-mode thread that has been granted the I2S device can issue a single i2s_trigger() call naming the unwired direction and cause a load from address 0 in kernel mode. Among the Espressif parts that carry this driver, userspace is available in-tree only on RISC-V SoCs with CONFIG_RISCV_PMP, and v4.4.0 is the first release where that is buildable: the ESP32-C6 HPCORE selects RISCV_PMP when it is not built for MCUboot. ESP32-C5 in v4.4.x carries the same PMP-region and userspace linker support but does not select RISCV_PMP by default. Espressif Xtensa targets do not support Zephyr userspace, and in a non-userspace build the bad direction can only come from in-kernel application code.

The impact is limited to availability: the access is a read at offset 0 of the missing stream structure, so there is no attacker-controlled offset, no write primitive and no information disclosure. With the default fatal-error handler the resulting exception halts the system, giving an unprivileged user-mode thread a system-wide denial of service. The fix adds the same pointer check the I2S_DIR_BOTH branch already performed and returns -ENOSYS for a direction the instance does not implement; the driver's other entry points (i2s_esp32_config_check(), i2s_esp32_config_get(), i2s_esp32_read(), i2s_esp32_write()) already guarded the pointers, and a static audit found no equivalent unguarded path.

The driver defect is older than the affected range. The unguarded dereference is present from v4.2.0 (reached through i2s_esp32_trigger_stream(), whose if (stream) guard tests the address of a struct member and is never false) and takes its present i2s_esp32_trigger_check() form in v4.3.0. No in-tree Espressif configuration before v4.4.0 can run a user-mode thread, so in v4.2.x and v4.3.x the direction argument can only come from trusted kernel code. Those releases carry the bug but are not listed as affected; the fix has also been merged to v4.3-branch as hardening.
Published: 2026-10-11
Score: 5.5 Medium
EPSS: n/a
KEV: No
Impact: Denial of Service (system‑wide kernel crash)
Action: Patch
AI Analysis

Impact

A null pointer dereference occurs when the i2s_esp32_trigger_check() function accepts an unsupported direction and accesses a missing stream structure without verifying the pointer. The resulting read at address 0 causes a kernel exception that halts the system, delivering a complete system‑wide denial of service. The vulnerability does not lead to privilege escalation or information disclosure; it merely destabilizes the host.

Affected Systems

The flaw is present in the Zephyr RTOS I2S driver for Espressif ESP32 series chips, including ESP32, ESP32-C5, and ESP32-C6. It affects builds that enable userspace (CONFIG_USERSPACE) and the associated RISC‑V PMP configuration enabled on ESP32‑C6 HPCORE and ESP32‑C5 when it is not built for MCUboot. The relevant Zephyr releases that contain the bug are v4.2.0 and later, up to the version that incorporated the hardening patch (v4.4.0).

Risk and Exploitability

The CVSS score of 5.5 indicates a medium severity issue. The EPSS score is not available, and the vulnerability is not listed in the CISA KEV catalog. Attackers who can obtain an unprivileged user‑mode thread with access to an I2S device can trigger the unsafe direction, provoking a crash. Since the exploit requires only a bad direction argument with no user‑controlled offset, the likelihood is low but non‑negligible in environments where userspace I2S usage is enabled. The vulnerability is limited to availability and does not permit code execution or data exfiltration.

Generated by OpenCVE AI on October 11, 2026 at 18:23 UTC.

Remediation

No solution or workaround provided in the CVE record.

OpenCVE Recommended Actions

  • Update Zephyr to a version that includes the bound‑check fix for the ESP32 I2S driver.
  • Rebuild the application with CONFIG_USERSPACE disabled if user‑mode i2s access is not required.
  • Remove or restrict the I2S device configuration in the device tree so that only implemented directions are exposed, preventing the bad direction trigger from being reachable.

Generated by OpenCVE AI on October 11, 2026 at 18:23 UTC.

Tracking

Sign in to view the affected projects.

Advisories

No advisories yet.

History

Sun, 11 Oct 2026 18:45:00 +0000

Type Values Removed Values Added
First Time appeared Zephyrproject
Zephyrproject zephyr
Vendors & Products Zephyrproject
Zephyrproject zephyr

Sun, 11 Oct 2026 17:30:00 +0000

Type Values Removed Values Added
Description i2s_esp32_trigger_check() in drivers/i2s/i2s_esp32.c validates the requested direction only for I2S_DIR_BOTH. The I2S_DIR_RX and I2S_DIR_TX branches read dev_cfg->rx.data->configured / dev_cfg->tx.data->configured without first checking the stream pointers. The device instantiation macro I2S_ESP32_STREAM_INIT() sets both .conf and .data to NULL for a direction the devicetree does not describe, so on an instance that wires only one direction — the normal shape for audio output or a worldsemi,ws2812-i2s LED strip — the other direction dereferences a NULL pointer instead of returning an error. i2s_trigger() is a Zephyr syscall, and z_vrfy_i2s_trigger() in drivers/i2s/i2s_handlers.c validates only the device object and the presence of the trigger API pointer; the dir argument is passed to the driver unvalidated. On a build with CONFIG_USERSPACE enabled, a user-mode thread that has been granted the I2S device can issue a single i2s_trigger() call naming the unwired direction and cause a load from address 0 in kernel mode. Among the Espressif parts that carry this driver, userspace is available in-tree only on RISC-V SoCs with CONFIG_RISCV_PMP, and v4.4.0 is the first release where that is buildable: the ESP32-C6 HPCORE selects RISCV_PMP when it is not built for MCUboot. ESP32-C5 in v4.4.x carries the same PMP-region and userspace linker support but does not select RISCV_PMP by default. Espressif Xtensa targets do not support Zephyr userspace, and in a non-userspace build the bad direction can only come from in-kernel application code. The impact is limited to availability: the access is a read at offset 0 of the missing stream structure, so there is no attacker-controlled offset, no write primitive and no information disclosure. With the default fatal-error handler the resulting exception halts the system, giving an unprivileged user-mode thread a system-wide denial of service. The fix adds the same pointer check the I2S_DIR_BOTH branch already performed and returns -ENOSYS for a direction the instance does not implement; the driver's other entry points (i2s_esp32_config_check(), i2s_esp32_config_get(), i2s_esp32_read(), i2s_esp32_write()) already guarded the pointers, and a static audit found no equivalent unguarded path. The driver defect is older than the affected range. The unguarded dereference is present from v4.2.0 (reached through i2s_esp32_trigger_stream(), whose if (stream) guard tests the address of a struct member and is never false) and takes its present i2s_esp32_trigger_check() form in v4.3.0. No in-tree Espressif configuration before v4.4.0 can run a user-mode thread, so in v4.2.x and v4.3.x the direction argument can only come from trusted kernel code. Those releases carry the bug but are not listed as affected; the fix has also been merged to v4.3-branch as hardening.
Title NULL pointer dereference in the ESP32 I2S driver when triggering an unsupported direction
Weaknesses CWE-476
References
Metrics cvssV3_1

{'score': 5.5, 'vector': 'CVSS:3.1/AV:L/AC:L/PR:L/UI:N/S:U/C:N/I:N/A:H'}

Subscriptions

Zephyrproject Zephyr
cve-icon MITRE

Status: PUBLISHED

Assigner: zephyr

Published:

Updated: 2026-10-11T17:15:01.878Z

Reserved: 2026-08-13T13:46:28.028Z

Link: CVE-2026-19737

cve-icon Vulnrichment

No data.

cve-icon NVD

Status : Received

Published: 2026-10-11T18:16:58.930

Modified: 2026-10-11T18:16:58.930

Link: CVE-2026-19737

cve-icon Redhat

No data.

cve-icon OpenCVE Enrichment

Updated: 2026-10-11T18:30:19Z

Weaknesses