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().
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History

Mon, 17 Aug 2026 17:45:00 +0000

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

Mon, 17 Aug 2026 16:30:00 +0000

Type Values Removed Values Added
Description 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().
Title PL011 UART error interrupts never cleared, enabling an external-peer interrupt-storm denial of service
Weaknesses CWE-835
References
Metrics cvssV3_1

{'score': 4.6, 'vector': 'CVSS:3.1/AV:P/AC:L/PR:N/UI:N/S:U/C:N/I:N/A:H'}


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cve-icon MITRE

Status: PUBLISHED

Assigner: zephyr

Published:

Updated: 2026-08-17T18:27:37.225Z

Reserved: 2026-06-18T15:22:24.098Z

Link: CVE-2026-12629

cve-icon Vulnrichment

No data.

cve-icon NVD

Status : Received

Published: 2026-08-17T17:16:39.010

Modified: 2026-08-17T17:16:39.010

Link: CVE-2026-12629

cve-icon Redhat

No data.

cve-icon OpenCVE Enrichment

Updated: 2026-08-17T17:45:03Z

Weaknesses