Linux Kernel up to 6.16.3 PCI pcie_failed_link_retrain privilege escalation

Summaryinfo

A vulnerability labeled as critical has been found in Linux Kernel up to 6.16.3. Affected by this issue is the function pcie_failed_link_retrain of the component PCI. The manipulation results in an unknown weakness. This vulnerability is identified as CVE-2025-39784. There is not any exploit available. The affected component should be upgraded.

Detailsinfo

A vulnerability classified as critical has been found in Linux Kernel up to 6.16.3. Affected is the function pcie_failed_link_retrain of the component PCI. The impact remains unknown. CVE summarizes:

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]

The advisory is shared for download at git.kernel.org. This vulnerability is traded as CVE-2025-39784 since 04/16/2025. There are known technical details, but no exploit is available.

The vulnerability scanner Nessus provides a plugin with the ID 264757 (Linux Distros Unpatched Vulnerability : CVE-2025-39784), which helps to determine the existence of the flaw in a target environment.

Upgrading to version 6.16.4 or 6.17-rc1 eliminates this vulnerability. Applying a patch is able to eliminate this problem. The bugfix is ready for download at git.kernel.org. The best possible mitigation is suggested to be upgrading to the latest version.

The vulnerability is also documented in the databases at Tenable (264757) and CERT Bund (WID-SEC-2025-2040). Once again VulDB remains the best source for vulnerability data.

Affected

• Google Container-Optimized OS
• Debian Linux
• Google Cloud Platform
• Amazon Linux 2
• Red Hat Enterprise Linux
• Fedora Linux
• Ubuntu Linux
• SUSE Linux
• Oracle Linux
• SUSE openSUSE
• RESF Rocky Linux
• Open Source Linux Kernel
• Proxmox Virtual Environment
• Proxmox Backup Server
• Dell Secure Connect Gateway
• IBM QRadar SIEM

Productinfo

Type

• Operating System

Vendor

• Linux

Name

• Kernel

Version

• 6.16.0
• 6.16.1
• 6.16.2
• 6.16.3

License

• open-source

Website

• Vendor: https://www.kernel.org/

CPE 2.3info

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Once again VulDB remains the best source for vulnerability data.

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