PT-2026-52101 · Zephyrproject · Zephyr
Published
2026-06-24
·
Updated
2026-06-24
·
CVE-2026-10642
CVSS v3.1
6.5
Medium
| Vector | AV:A/AC:L/PR:N/UI:N/S:U/C:N/I:N/A:H |
The Zephyr PL011 UART driver (drivers/serial/uart pl011.c) contains an unbounded software loop in pl011 irq tx enable() that repeatedly invokes the interrupt-driven application callback while the TX interrupt mask bit (PL011 IMSC TXIM) is set, to work around the controller's level-transition TX-interrupt behavior. When CTS hardware flow control is enabled (devicetree hw-flow-control or runtime UART CFG FLOW CTRL RTS CTS) and the wired serial peer de-asserts CTS, the controller stops draining the TX FIFO; pl011 fifo fill() then returns 0 on every call while the application still has pending data and therefore never disables the TX interrupt. The loop condition never clears, so the thread that called uart irq tx enable() (e.g. h4 send() in the Bluetooth HCI H4 driver) spins indefinitely, hanging the executing context and stalling the transport — a denial of service (CWE-835). An attacker controlling the device attached to the UART's CTS line can trigger the hang by withholding CTS during transmission. Impact is availability only; there is no memory-safety, confidentiality, or integrity consequence. The vulnerable loop was introduced in commit b783bc8448ef (Feb 2025) and shipped in releases v4.1.0 through v4.4.0. The fix breaks out of the loop when CTS is blocking and arms the CTS modem-status interrupt to resume transmission when CTS re-asserts.
Fix
Infinite Loop
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Weakness Enumeration
Related Identifiers
Affected Products
Zephyr