CVE-2024-47742 Information

Description

In the Linux kernel the following vulnerability has been resolved:

firmware_loader: Block path traversal

Most firmware names are hardcoded strings or are constructed from fairly constrained format strings where the dynamic parts are just some hex numbers or such.

However there are a couple codepaths in the kernel where firmware file names contain string components that are passed through from a device or semi-privileged userspace; the ones I could find (not counting interfaces that require root privileges) are:

• lpfc_sli4_request_firmware_update() seems to construct the firmware filename from \ModelName\ a string that was previously parsed out of some descriptor (\Vital Product Data) in lpfc_fill_vpd()
• nfp_net_fw_find() seems to construct a firmware filename from a model name coming from nfp_hwinfo_lookup(pf->hwinfo ffw.partno) which I think parses some descriptor that was read from the device. (But this case likely isn’t exploitable because the format string looks like etronome/nic_%s\ and there shouldn’t be any folders starting with etronome/nic_. The previous case was different because there the %s\ is at the start of the format string.)
• module_flash_fw_schedule() is reachable from the ETHTOOL_MSG_MODULE_FW_FLASH_ACT netlink command which is marked as GENL_UNS_ADMIN_PERM (meaning CAP_NET_ADMIN inside a user namespace is enough to pass the privilege check) and takes a userspace-provided firmware name. (But I think to reach this case you need to have CAP_NET_ADMIN over a network namespace that a special kind of ethernet device is mapped into so I think this is not a viable attack path in practice.)

Fix it by rejecting any firmware names containing ..\ path components.

For what it’s worth I went looking and haven’t found any USB device drivers that use the firmware loader dangerously.

CVSS Vector

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

Reference

https://git.kernel.org/stable/c/c30558e6c5c9ad6c86459d9acce1520ceeab9ea6 https://git.kernel.org/stable/c/a77fc4acfd49fc6076e565445b2bc5fdc3244da4 https://git.kernel.org/stable/c/3d2411f4edcb649eaf232160db459bb4770b5251 https://git.kernel.org/stable/c/7420c1bf7fc784e587b87329cc6dfa3dca537aa4 https://git.kernel.org/stable/c/28f1cd94d3f1092728fb775a0fe26c5f1ac2ebeb https://git.kernel.org/stable/c/6c4e13fdfcab34811c3143a0a03c05fec4e870ec https://git.kernel.org/stable/c/f0e5311aa8022107d63c54e2f03684ec097d1394

Attack Complexity

LOW

Privileges Required

LOW

User Interaction Required

LOW

Scope

NONE

Confidentiality Impact

UNCHANGED

Integrity Impact

HIGH

Availability Impact

HIGH

Base Score

HIGH

Base Severity

7.8