How severe is CVE-2026-10642?

CVE-2026-10642 has a CVSS 3.x base score of 6.5, rated medium severity. It is exploitable over an adjacent network with low attack complexity, requires no privileges and no user interaction. Impact on confidentiality is none, integrity none, and availability high.

Is CVE-2026-10642 being actively exploited?

It is not currently listed in CISA's KEV catalog. Its EPSS exploit-prediction score is 0% (8th percentile), an estimate of the probability of exploitation in the next 30 days.

What products are affected by CVE-2026-10642?

CVE-2026-10642 affects Zephyrproject Zephyr. See the affected-products list for the exact vulnerable versions.

How do I fix CVE-2026-10642?

Review the linked vendor and NVD advisories for patched versions and mitigations, then upgrade or apply the recommended workaround.

Does CVE-2026-10642 have an EU (EUVD) identifier?

Yes. CVE-2026-10642 is tracked in the ENISA EU Vulnerability Database (EUVD) as EUVD-2026-39106.

When was CVE-2026-10642 published?

CVE-2026-10642 was published on 2026-06-24 and last updated on 2026-07-02.

CVE-2026-10642

CVE-2026-10642 is a medium-severity vulnerability in Zephyrproject Zephyr with a CVSS 3.x base score of 6.5. It is not currently listed as actively exploited by CISA, and its EPSS exploit-prediction score is low. The underlying weakness is classified as CWE-835.

Key facts

Severity: Medium (CVSS 3.x base score 6.5)
EPSS exploit prediction: 0% (8th percentile)
Actively exploited: Not listed in CISA KEV
EU (EUVD) id: EUVD-2026-39106
Weakness: CWE-835
Affected product: Zephyrproject Zephyr
Published: 2026-06-24
Last modified: 2026-07-02

Description

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.

Frequently asked questions

What is CVE-2026-10642?: 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.
How severe is CVE-2026-10642?: CVE-2026-10642 has a CVSS 3.x base score of 6.5, rated medium severity. It is exploitable over an adjacent network with low attack complexity, requires no privileges and no user interaction. Impact on confidentiality is none, integrity none, and availability high.
Is CVE-2026-10642 being actively exploited?: It is not currently listed in CISA's KEV catalog. Its EPSS exploit-prediction score is 0% (8th percentile), an estimate of the probability of exploitation in the next 30 days.
What products are affected by CVE-2026-10642?: CVE-2026-10642 affects Zephyrproject Zephyr. See the affected-products list for the exact vulnerable versions.
How do I fix CVE-2026-10642?: Review the linked vendor and NVD advisories for patched versions and mitigations, then upgrade or apply the recommended workaround.
Does CVE-2026-10642 have an EU (EUVD) identifier?: Yes. CVE-2026-10642 is tracked in the ENISA EU Vulnerability Database (EUVD) as EUVD-2026-39106.
When was CVE-2026-10642 published?: CVE-2026-10642 was published on 2026-06-24 and last updated on 2026-07-02.

References

Affected products (1)

cpe:2.3:o:zephyrproject:zephyr:*:*:*:*:*:*:*:*

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