CVE-2025-39724: debian linux — Fix

Description

In the Linux kernel, the following vulnerability has been resolved: serial: 8250: fix panic due to PSLVERR When the PSLVERR_RESP_EN parameter is set to 1, the device generates an error response if an attempt is made to read an empty RBR (Receive Buffer Register) while the FIFO is enabled. In serial8250_do_startup(), calling serial_port_out(port, UART_LCR, UART_LCR_WLEN8) triggers dw8250_check_lcr(), which invokes dw8250_force_idle() and serial8250_clear_and_reinit_fifos(). The latter function enables the FIFO via serial_out(p, UART_FCR, p->fcr). Execution proceeds to the serial_port_in(port, UART_RX). This satisfies the PSLVERR trigger condition. When another CPU (e.g., using printk()) is accessing the UART (UART is busy), the current CPU fails the check (value & ~UART_LCR_SPAR) == (lcr & ~UART_LCR_SPAR) in dw8250_check_lcr(), causing it to enter dw8250_force_idle(). Put serial_port_out(port, UART_LCR, UART_LCR_WLEN8) under the port->lock to fix this issue. Panic backtrace: [ 0.442336] Oops - unknown exception [#1] [ 0.442343] epc : dw8250_serial_in32+0x1e/0x4a [ 0.442351] ra : serial8250_do_startup+0x2c8/0x88e ... [ 0.442416] console_on_rootfs+0x26/0x70

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CVSS v3.1 Score

5.5

MEDIUM

CVSS:3.1/AV:L/AC:L/PR:L/UI:N/S:U/C:N/I:N/A:H

Affected Products

Vendor	Product	Versions
linux	linux_kernel	3.10.48 — 3.11
linux	linux_kernel	3.12.24 — 5.4.297
linux	linux_kernel	5.5 — 5.10.241
linux	linux_kernel	5.11 — 5.15.190
linux	linux_kernel	5.16 — 6.1.149
linux	linux_kernel	6.2 — 6.6.103
linux	linux_kernel	6.7 — 6.12.44
linux	linux_kernel	6.13 — 6.16.4
debian	debian_linux	All

References

Advisories & Patches

https://git.kernel.org/stable/c/0b882f00655afefbc7729c6b5aec86f7a5473a3d https://git.kernel.org/stable/c/38c0ea484dedb58cb3a4391229933e16be0d1031 https://git.kernel.org/stable/c/68c4613e89f000e8198f9ace643082c697921c9f https://git.kernel.org/stable/c/7f8fdd4dbffc05982b96caf586f77a014b2a9353 https://git.kernel.org/stable/c/8e2739478c164147d0774802008528d9e03fb802 https://git.kernel.org/stable/c/b8ca8e3f75ede308b4d49a6ca5081460be01bdb5 https://git.kernel.org/stable/c/c826943abf473a3f7260fbadfad65e44db475460 https://git.kernel.org/stable/c/cb7b3633ed749db8e56f475f43c960652cbd6882

Other References

https://lists.debian.org/debian-lts-announce/2025/10/msg00007.html https://lists.debian.org/debian-lts-announce/2025/10/msg00008.html https://cert-portal.siemens.com/productcert/html/ssa-032379.html https://cert-portal.siemens.com/productcert/html/ssa-082556.html

Frequently Asked Questions

What is CVE-2025-39724? +

In the Linux kernel, the following vulnerability has been resolved: serial: 8250: fix panic due to PSLVERR When the PSLVERR_RESP_EN parameter is set to 1, the device generates an error response if an attempt is made to read an empty RBR (Receive Buffer Register) while the FIFO is enabled. In serial8250_do_startup(), calling serial_port_out(port, UART_LCR, UART_LCR_WLEN8) triggers dw8250_check_lcr(), which invokes dw8250_force_idle() and serial8250_clear_and_reinit_fifos(). The latter function enables the FIFO via serial_out(p, UART_FCR, p->fcr). Execution proceeds to the serial_port_in(port, UART_RX). This satisfies the PSLVERR trigger condition. When another CPU (e.g., using printk()) is accessing the UART (UART is busy), the current CPU fails the check (value & ~UART_LCR_SPAR) == (lcr & ~UART_LCR_SPAR) in dw8250_check_lcr(), causing it to enter dw8250_force_idle(). Put serial_port_out(port, UART_LCR, UART_LCR_WLEN8) under the port->lock to fix this issue. Panic backtrace: [ 0.442336] Oops - unknown exception [#1] [ 0.442343] epc : dw8250_serial_in32+0x1e/0x4a [ 0.442351] ra : serial8250_do_startup+0x2c8/0x88e ... [ 0.442416] console_on_rootfs+0x26/0x70 It has a CVSS v3.1 base score of 5.5 (MEDIUM).

How severe is CVE-2025-39724? +

CVE-2025-39724 has a CVSS v3.1 score of 5.5 out of 10, rated MEDIUM. This is a medium-severity vulnerability that should be remediated as part of regular maintenance.

What products are affected by CVE-2025-39724? +

CVE-2025-39724 affects products from debian, linux, specifically: debian_linux, linux_kernel. Check the affected products table above for specific version ranges.

How do I check if I'm vulnerable to CVE-2025-39724? +

You can use Secably's free Website Scanner to check your website for known vulnerabilities. For infrastructure scanning, use the Port Scanner to identify exposed services that may be affected. Check the vendor advisories linked above for specific patch and version information.

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CVE-2025-39724