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[arm64/riscv64 + EFI] systemd-boot loads unverified device tree blobs when secure boot is enabled in type #1 BLS setups

Low
bluca published GHSA-6m6p-rjcq-334c Sep 20, 2023

Package

systemd

Affected versions

>= 250

Patched versions

255 254.4 253.11 252.17 251.19 250.13

Description

Impact

On arm64 and riscv64, systemd-boot allows a local user to specify a device tree blob and loads it, even when secure boot mode is enabled when using type #1 BLS setups. DTBs are loaded and parsed by the kernel before ExitBootServices(), and the kernel itself disallows loading DTBs via the dtb= kernel command line option when secure boot is enabled.

This feature was introduced in v250 by: 6e86342bb82

As far as we are aware, there are no Shim-trusted arm64/riscv64 systemd-boot binaries published anywhere, so the severity and impact are low, as it affects only local self-signed secure boot deployments of systemd-boot on arm64/riscv64.

Patches

Fixed in main and 254.4 253.11 252.17 251.19 250.13

#29228
systemd/systemd-stable#324
systemd/systemd-stable#325
systemd/systemd-stable#326
systemd/systemd-stable#327
systemd/systemd-stable#328

Workarounds

Use type #2 BLS setups

References

#29228

Severity

Low

CVSS overall score

This score calculates overall vulnerability severity from 0 to 10 and is based on the Common Vulnerability Scoring System (CVSS).
/ 10

CVSS v3 base metrics

Attack vector
Physical
Attack complexity
Low
Privileges required
High
User interaction
Required
Scope
Unchanged
Confidentiality
None
Integrity
Low
Availability
None

CVSS v3 base metrics

Attack vector: More severe the more the remote (logically and physically) an attacker can be in order to exploit the vulnerability.
Attack complexity: More severe for the least complex attacks.
Privileges required: More severe if no privileges are required.
User interaction: More severe when no user interaction is required.
Scope: More severe when a scope change occurs, e.g. one vulnerable component impacts resources in components beyond its security scope.
Confidentiality: More severe when loss of data confidentiality is highest, measuring the level of data access available to an unauthorized user.
Integrity: More severe when loss of data integrity is the highest, measuring the consequence of data modification possible by an unauthorized user.
Availability: More severe when the loss of impacted component availability is highest.
CVSS:3.1/AV:P/AC:L/PR:H/UI:R/S:U/C:N/I:L/A:N

CVE ID

No known CVE

Weaknesses

No CWEs

Credits