Integer underflow in Linux kernel - CVE-2026-63883
Published: July 20, 2026
Vulnerability identifier: #VU138766
CSH Severity: Low
CVSS v4.0: CVSS:4.0/AV:L/AC:L/AT:N/PR:L/UI:N/VC:L/VI:N/VA:N/SC:N/SI:N/SA:N/E:U/U:Clear
CVE-ID: CVE-2026-63883
CWE-ID: CWE-191
Exploitation vector: Local access
Exploit availability:
No public exploit available
Vendor: Linux Foundation
Affected software:
Linux kernel
Linux kernel
Detailed vulnerability description
The vulnerability allows a local user to disclose stale buffer data.
The vulnerability exists due to an integer underflow in qcom_geni_serial_handle_tx_dma() when handling a DMA completion interrupt after uart_flush_buffer() resets the transmit buffer. A local user can trigger a flush before DMA completion is processed to disclose stale buffer data.
The issue is caused by a race condition between transmit buffer flushing and delayed DMA completion handling.
How to mitigate CVE-2026-63883
Install security update from vendor's repository.
Sources
- https://git.kernel.org/stable/c/0d2c41a8b00934ddf8a7c1b4cf72dffa1e629c46
- https://git.kernel.org/stable/c/452d6fa37ae9b021f4f6d397dbae077f7296f6f4
- https://git.kernel.org/stable/c/654f45a8569f3cd6ff20bd724a18e0cce65893ba
- https://git.kernel.org/stable/c/b1159dce10b38eb795e4c96cdc4d34b83cec81c5
- https://git.kernel.org/stable/c/c91ea13375f70f6271a0183445e34e83b8f4d8f7