🛡️ CVE-2025-39784 — kernel

🟡 CVSS 5.5 — Medium ✅ No Known Exploit NVD
5.5
CVSS Score
0 Low4 Medium7 High9 Critical10

Description

PCI: Fix link speed calculation on retrain failure

In the Linux kernel, the following vulnerability has been resolved:

PCI: Fix link speed calculation on retrain failure

When pcie_failed_link_retrain() fails to retrain, it tries to revert to the

previous link speed. However it calculates that speed from the Link

Control 2 register without masking out non-speed bits first.

PCIE_LNKCTL2_TLS2SPEED() converts such incorrect values to

PCI_SPEED_UNKNOWN (0xff), which in turn causes a WARN splat in

pcie_set_target_speed():

pci 0000:00:01.1: [1022:14ed] type 01 class 0x060400 PCIe Root Port

pci 0000:00:01.1: broken device, retraining non-functional downstream link at 2.5GT/s

pci 0000:00:01.1: retraining failed

WARNING: CPU: 1 PID: 1 at drivers/pci/pcie/bwctrl.c:168 pcie_set_target_speed

RDX: 0000000000000001 RSI: 00000000000000ff RDI: ffff9acd82efa000

pcie_failed_link_retrain

pci_device_add

pci_scan_single_device

Mask out the non-speed bits in PCIE_LNKCTL2_TLS2SPEED() and

PCIE_LNKCAP_SLS2SPEED() so they don't incorrectly return PCI_SPEED_UNKNOWN.

[bhelgaas: commit log, add details from https://lore.kernel.org/r/1c92ef6bcb314ee6977839b46b393282e4f52e74.1750684771.git.lukas@wunner.de]

How this vulnerability can be exploited

This issue can be reached with local access to the system, attack complexity is low, an attacker needs low-level privileges on the target. No user interaction is required. The scope is unchanged, so the impact stays within the vulnerable component. Rated impact: confidentiality none, integrity none, availability high.

Affected software

CVE-2025-39784 is recorded against 2 packages.

  • kernel (from 6.13.0 up to 6.16.4)
  • linux-kernel (from 6.13 up to 6.16.4)

Timeline and source

Published on 11 September 2025 and last revised on 15 July 2026. No public exploit is currently recorded for this entry. A vendor advisory or fix has been published. Record sourced from NVD.

References

git.kernel.org (Web)
git.kernel.org (Web)
github.com (Advisory)
nvd.nist.gov (Advisory)
git.kernel.org (Package)

CVE-2025-39784 on other distributions

Each distribution ships its own build and its own fixed version. Pick the one you run:

Details

Severity Medium
CVSS Score 5.5
CVSS Vector CVSS:3.1/AV:L/AC:L/PR:L/UI:N/S:U/C:N/I:N/A:H
CWE N/A
Public Exploit ✅ No
Source NVD
Published 2025-09-11
Updated 2026-08-12
Modified 2026-07-15

Affected Packages

Software From version Fixed in
kernel 6.13.0 6.16.4
linux-kernel 6.13 6.16.4

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