CVE-2026-93206
Low risk· EPSS 8%Exploitation Probability (EPSS)
Low risk8th percentile - higher than 8% of all known CVEs
Summary
In the Linux kernel, the procfs interface for reading PCI config space (proc_bus_pci_read) checked CAP_SYS_ADMIN based on the credentials of the task calling read(), not the process that opened the file. A privileged process could open the file and pass the file descriptor to an unprivileged process, which could then read the entire config space. The fix uses file_ns_capable() to check the credentials recorded in file->f_cred at open time, aligning with sysfs behavior.
Risk Assessment
An unprivileged process may gain access to the full PCI device config space, potentially leading to information disclosure or facilitating further attacks. The risk occurs when a privileged process passes a file descriptor to a less privileged process.
Recommendation
Update the Linux kernel to a version containing the fix. Until then, avoid passing file descriptors from /proc/bus/pci to unprivileged processes.
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Original NVD description (English source)
In the Linux kernel, the following vulnerability has been resolved: PCI/proc: Use file_ns_capable() when checking config space read access proc_bus_pci_read() decides how much of the config space is readable based on capable(CAP_SYS_ADMIN), which checks the credentials of the task calling read(), not the credentials of the process that opened the file. The sysfs equivalent, pci_read_config(), has checked the credentials of the opening process since commit de139a339395 ("pci: check caps from sysfs file open to read device dependent config space"), so a privileged process can open the config space file and pass the file descriptor to an unprivileged process (for example, a process running a KVM guest with an assigned device), which can then read the entire config space. The check was subsequently routed through the LSM framework in commit 47970b1b2aa6 ("pci: use security_capable() when checking capablities during config space read") and converted to the dedicated helper in commit ab0fa82b2df9 ("pci-sysfs: use proper file capability helper function"). Thus, the two interfaces check the same capability against different credentials. Checking the credentials of the task calling read() makes the outcome depend on who reads rather than who opened, so the restriction is bypassed whenever a more privileged process reads through the descriptor. Checking the credentials recorded in file->f_cred settles the decision at open() time and ties it to the file, where it cannot change with the caller. Use file_ns_capable() to check CAP_SYS_ADMIN against the credentials in effect when the file was opened, bringing the procfs interface in line with the sysfs behaviour. As a result, a file descriptor opened by a privileged process and passed to an unprivileged one now allows the entire config space to be read through procfs, matching sysfs.
Vulnerability data from NVD (NIST) · CISA KEV · EPSS