# CVE-2026-12629: PL011 UART error interrupts never cleared, enabling an external-peer interrupt-storm denial of service

Status: published. Published: 2026-08-17. Updated: 2026-11-04.

The ARM PL011 UART driver in drivers/serial/uart_pl011.c fails to acknowledge receive error interrupts. On the PL011, the framing, parity, break, and overrun error interrupts (PL011_IMSC_ERROR_MASK) are cleared only by writing the interrupt-clear register UARTICR; reading the data register clears the RX interrupt and the per-byte RSR status but not the error interrupt status in MIS. The interrupt service routine pl011_isr() acknowledged only the CTS modem-status interrupt and never wrote icr for the error bits, so an asserted error interrupt remains pending after the ISR returns.

When an application enables error-interrupt reporting via the public uart_irq_err_enable() API, an attacker who controls the serial peer can deterministically assert these error bits by injecting line errors on the RX line — a baud/stop-bit mismatch or mid-character break (framing/break error), a flipped parity bit (parity error), or FIFO flooding (overrun error). Because the error interrupt is never cleared, the interrupt line stays asserted and the CPU re-enters pl011_isr() immediately and indefinitely, producing an interrupt-storm livelock from which the core makes no forward progress.

The impact is an availability-only denial of service (permanent hang), reachable from an external or removable UART peer. Exploitation is gated by configuration: the error interrupt is off by default and no in-tree subsystem enables it, so only applications that explicitly call uart_irq_err_enable() on a PL011-based, interrupt-driven port are affected. The fix makes pl011_isr() acknowledge the pending error bits via uart->icr, breaking the loop, and additionally clears the latched RSR status in pl011_err_check().

## Remediation

- fix: The reporting source identifies this reference as a patch. Check the advisory for affected versions and supported release branches. (source: CNA: zephyr) — https://github.com/zephyrproject-rtos/zephyr/commit/1069b6822ac90da2b9e6dc8a5bbe3873e9f92818

## Affected products and versions

- zephyrproject / zephyr (zephyr): ≥ 1.14.0; < 4.3.2 (affected, semver); ≥ 4.4.0; < 4.4.2 (affected, semver). Source: CNA: zephyr

## Severity and prioritization

- CVSS 3.1: 4.6 (medium); CVSS:3.1/AV:P/AC:L/PR:N/UI:N/S:U/C:N/I:N/A:H; source: CNA: zephyr

- CVSS 3.1: 4.6 (medium); CVSS:3.1/AV:P/AC:L/PR:N/UI:N/S:U/C:N/I:N/A:H; source: NVD: vulnerabilities@zephyrproject.org

- CISA KEV: No listing in collected sources

- EPSS: 0.23% as of 2026-11-03; percentile 13.95%

- SSVC: exploitation none; automatable no; technical impact partial; source ADP: CISA-ADP

- Weaknesses: CWE-835

## Exploit evidence

No exploit evidence in collected sources. This is not proof of no exploitation.

## References

- https://github.com/zephyrproject-rtos/zephyr/commit/1069b6822ac90da2b9e6dc8a5bbe3873e9f92818 (CNA: zephyr; patch)

- https://github.com/zephyrproject-rtos/zephyr/security/advisories/GHSA-36rp-2hcp-f5hv (CNA: zephyr)

- https://github.com/zephyrproject-rtos/zephyr/commit/1069b6822ac90da2b9e6dc8a5bbe3873e9f92818 (vulnerabilities@zephyrproject.org)

- https://github.com/zephyrproject-rtos/zephyr/security/advisories/GHSA-36rp-2hcp-f5hv (vulnerabilities@zephyrproject.org)

## Provenance

- CNA: zephyr: https://www.cve.org/CVERecord?id=CVE-2026-12629; retrieved 2026-11-04; source updated 2026-11-04

- NVD: https://nvd.nist.gov/vuln/detail/CVE-2026-12629; retrieved 2026-11-04; source updated 2026-11-04

- FIRST EPSS: https://api.first.org/data/v1/epss?cve=CVE-2026-12629; retrieved 2026-11-04; source updated Not reported

Revision: 3bd6d28166338c1738b6f6e79a190b7c18cefc099850757afb6c6cd10668f481

Canonical: https://y2.dev/cve/CVE-2026-12629

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