Executive brief
Entrust nShield hardware security modules (HSMs)—devices used to protect and manage cryptographic keys for enterprises—allow a physically nearby attacker to gain full administrative control by booting from a USB device. The vulnerability stems from weak default settings in the Legacy GRUB bootloader that do not prevent unauthorized boot media. Exploitation gives attackers complete control over the HSM, enabling them to steal keys, modify firmware, and potentially compromise the entire organization's encryption infrastructure without detection.
Technical details
The vulnerability is a privilege escalation flaw in the Legacy GRUB bootloader used by Entrust nShield HSM appliances (Connect XC, 5c, and HSMi). An attacker with physical access can insert a USB device containing a valid root filesystem and boot the appliance into the GRUB shell by hitting 'c' during boot, bypassing authentication. The insecure default bootloader configuration allows unauthenticated access to the boot menu and does not verify the integrity or source of boot media. From the GRUB shell, an attacker gains root-level access to the appliance, enabling full compromise of the HSM including cryptographic key theft, firmware modification, and persistent backdoors. Patches are available in version 13.6.12 (LTS) and 13.9.0 (STS).
Affected products
- Entrust nShield Connect XC through 13.6.11, patched in 13.6.12 (LTS) and 13.9.0 (STS)
- Entrust nShield 5c through 13.6.11, patched in 13.6.12 (LTS) and 13.9.0 (STS)
- Entrust nShield HSMi through 13.6.11, or 13.7, patched in 13.6.12 (LTS) and 13.9.0 (STS)
Timeline
- 2025-12-02: disclosed
- 2025-12-02: patched: Patches available in nShield 13.6.12 (LTS) and 13.9.0 (STS)