Improper Scrubbing of Sensitive Data from Decommissioned Device

Description

Improper Scrubbing of Sensitive Data from Decommissioned Device occurs when a product lacks adequate capability for administrators to remove sensitive data when equipment is taken out of service. This absence, inadequacy, or incorrectness of scrubbing functionality creates vulnerability exposure. Decommissioning best practices and regulatory compliance often mandate data removal before equipment retirement. When sensitive information isn't properly erased, malicious actors can retrieve it from disposed or recycled equipment.

Risk

Inadequate data scrubbing has severe security implications. Authentication credentials may be recovered. Network configurations may be exposed. Cryptographic keys may be extracted. Proprietary information may leak. Customer data may be compromised. Intellectual property may be stolen. Compliance violations may occur. Reputational damage may result from data breaches.

Solution

Incorporate comprehensive data scrubbing functionality during initial design rather than retrofitting later. Document storage locations, removal policies, and procedures in administrative guides or volatility statements. Provide utility tools for erasing sensitive data from non-accessible storage areas like EEPROMs. Implement cryptographic erasure where appropriate. Verify scrubbing effectiveness through testing.

Common Consequences

Impact	Details
Confidentiality	Scope: Confidentiality Read Memory - Adversaries gain unauthorized access to stored sensitive information from decommissioned devices.

Example Code

Vulnerable Code

// Vulnerable: Device without data scrubbing capability

#include <stdint.h>

#define EEPROM_BASE 0x50000000
#define EEPROM_SIZE 4096

// Sensitive data storage
typedef struct {
    uint8_t wifi_ssid[32];
    uint8_t wifi_password[64];
    uint8_t admin_password[32];
    uint8_t api_key[64];
    uint8_t encryption_key[32];
    uint8_t certificate[1024];
} device_credentials_t;

// VULNERABLE: No scrubbing function provided
// Device stores credentials permanently

void vulnerable_store_credentials(device_credentials_t* creds) {
    // Write credentials to EEPROM
    volatile uint8_t* eeprom = (volatile uint8_t*)EEPROM_BASE;
    memcpy((void*)eeprom, creds, sizeof(device_credentials_t));
}

void vulnerable_factory_reset(void) {
    // VULNERABLE: Only resets configuration flags
    // Does NOT erase credentials from EEPROM

    config_flags = DEFAULT_FLAGS;
    reboot_device();

    // Credentials remain in EEPROM!
    // When device is decommissioned, attacker can:
    // 1. Remove EEPROM chip
    // 2. Read it with programmer
    // 3. Extract all credentials
}

// VULNERABLE: No data destruction on decommission
void vulnerable_shutdown(void) {
    // Normal shutdown - data persists
    save_state_to_flash();
    power_down();
}

// Vulnerable: Hardware without secure erase capability

module vulnerable_secure_storage (
    input wire clk,
    input wire reset_n,
    input wire [7:0] addr,
    input wire [31:0] write_data,
    input wire write_enable,
    input wire read_enable,
    output reg [31:0] read_data
);

    // Non-volatile storage (NVM)
    reg [31:0] nvm_storage [0:255];

    // VULNERABLE: No secure erase command
    // Data persists indefinitely

    always @(posedge clk or negedge reset_n) begin
        if (!reset_n) begin
            // VULNERABLE: Reset does not clear NVM
            // Only clears volatile state
            read_data <= 32'h0;
        end
        else if (write_enable) begin
            nvm_storage[addr] <= write_data;
        end
        else if (read_enable) begin
            read_data <= nvm_storage[addr];
        end
    end

    // No command to securely erase all storage
    // No verification that data is actually erased
    // No zeroization on tamper or decommission

endmodule

// Vulnerable: Device with incomplete scrubbing
module vulnerable_partial_scrub (
    input wire clk,
    input wire reset_n,
    input wire scrub_command,
    input wire [7:0] scrub_addr,
    output reg scrub_complete
);

    reg [31:0] config_storage [0:63];    // Gets scrubbed
    reg [31:0] key_storage [0:31];       // VULNERABLE: NOT scrubbed
    reg [31:0] log_storage [0:127];      // VULNERABLE: NOT scrubbed

    always @(posedge clk or negedge reset_n) begin
        if (!reset_n) begin
            scrub_complete <= 1'b0;
        end
        else if (scrub_command) begin
            // VULNERABLE: Only scrubs config, misses keys and logs
            config_storage[scrub_addr] <= 32'h0;

            // key_storage and log_storage are NOT cleared!
            // Attacker can still recover:
            // - Encryption keys
            // - Access logs with user information
            // - Network credentials stored in logs

            scrub_complete <= 1'b1;
        end
    end

endmodule

Fixed Code

// Fixed: Device with comprehensive data scrubbing

#include <stdint.h>
#include <string.h>

#define EEPROM_BASE 0x50000000
#define EEPROM_SIZE 4096
#define SCRUB_PATTERN_COUNT 3

typedef struct {
    uint8_t wifi_ssid[32];
    uint8_t wifi_password[64];
    uint8_t admin_password[32];
    uint8_t api_key[64];
    uint8_t encryption_key[32];
    uint8_t certificate[1024];
} device_credentials_t;

// Documented storage locations for decommissioning
typedef struct {
    const char* name;
    uint32_t address;
    uint32_t size;
    bool contains_sensitive_data;
} storage_location_t;

static const storage_location_t storage_map[] = {
    {"Credentials", 0x0000, sizeof(device_credentials_t), true},
    {"Encryption Keys", 0x1000, 256, true},
    {"Logs", 0x2000, 1024, true},
    {"Configuration", 0x3000, 512, false},
    {NULL, 0, 0, false}
};

// FIXED: Secure erase with verification
static void secure_memset(volatile void* ptr, uint8_t value, size_t size) {
    volatile uint8_t* p = (volatile uint8_t*)ptr;
    while (size--) {
        *p++ = value;
    }
    // Memory barrier
    __asm__ volatile("" ::: "memory");
}

// FIXED: Multi-pass overwrite for secure erasure
static bool secure_erase_region(uint32_t address, uint32_t size) {
    volatile uint8_t* ptr = (volatile uint8_t*)(EEPROM_BASE + address);

    // Pattern 1: All zeros
    secure_memset(ptr, 0x00, size);
    if (!verify_pattern(ptr, 0x00, size)) return false;

    // Pattern 2: All ones
    secure_memset(ptr, 0xFF, size);
    if (!verify_pattern(ptr, 0xFF, size)) return false;

    // Pattern 3: Random data
    uint8_t* random_data = get_random_bytes(size);
    memcpy((void*)ptr, random_data, size);
    free(random_data);

    // Pattern 4: Final zeros
    secure_memset(ptr, 0x00, size);
    if (!verify_pattern(ptr, 0x00, size)) return false;

    return true;
}

// FIXED: Verify erasure
static bool verify_pattern(volatile uint8_t* ptr, uint8_t expected, size_t size) {
    for (size_t i = 0; i < size; i++) {
        if (ptr[i] != expected) {
            return false;
        }
    }
    return true;
}

// FIXED: Comprehensive scrubbing function
int secure_decommission(void) {
    int errors = 0;

    log_event("Starting secure decommission");

    // FIXED: Scrub all documented storage locations
    for (int i = 0; storage_map[i].name != NULL; i++) {
        log_event("Scrubbing: %s", storage_map[i].name);

        if (!secure_erase_region(storage_map[i].address, storage_map[i].size)) {
            log_error("Failed to scrub: %s", storage_map[i].name);
            errors++;
        }
    }

    // FIXED: Clear RAM containing sensitive data
    clear_sensitive_ram();

    // FIXED: Invalidate encryption keys in hardware
    invalidate_hw_keys();

    // FIXED: Clear any cached credentials
    clear_credential_cache();

    // FIXED: Generate report
    generate_decommission_report();

    if (errors == 0) {
        log_event("Secure decommission complete");
        return 0;
    } else {
        log_error("Decommission incomplete: %d errors", errors);
        return -1;
    }
}

// FIXED: Factory reset that includes credential erasure
void secure_factory_reset(void) {
    // First, scrub all sensitive data
    secure_decommission();

    // Then reset configuration
    config_flags = DEFAULT_FLAGS;

    // Verify scrubbing before reboot
    if (!verify_all_scrubbed()) {
        // Fail secure - don't allow device to continue
        enter_lockout_mode();
    }

    reboot_device();
}

// Fixed: Hardware with comprehensive secure erase

module secure_storage_with_scrub (
    input wire clk,
    input wire reset_n,
    input wire [7:0] addr,
    input wire [31:0] write_data,
    input wire write_enable,
    input wire read_enable,
    // FIXED: Secure erase interface
    input wire scrub_all_command,
    input wire scrub_verify_command,
    output reg [31:0] read_data,
    output reg scrub_complete,
    output reg scrub_verified,
    output reg scrub_error
);

    // Storage arrays
    reg [31:0] config_storage [0:63];
    reg [31:0] key_storage [0:31];
    reg [31:0] log_storage [0:127];

    // FIXED: Scrubbing state machine
    reg [2:0] scrub_state;
    reg [7:0] scrub_index;
    reg [1:0] scrub_pass;

    parameter IDLE = 3'd0;
    parameter SCRUB_CONFIG = 3'd1;
    parameter SCRUB_KEYS = 3'd2;
    parameter SCRUB_LOGS = 3'd3;
    parameter VERIFY = 3'd4;
    parameter DONE = 3'd5;

    always @(posedge clk or negedge reset_n) begin
        if (!reset_n) begin
            scrub_state <= IDLE;
            scrub_complete <= 1'b0;
            scrub_verified <= 1'b0;
            scrub_error <= 1'b0;
            scrub_index <= 8'h0;
            scrub_pass <= 2'd0;
        end
        else begin
            case (scrub_state)
                IDLE: begin
                    scrub_complete <= 1'b0;
                    scrub_verified <= 1'b0;
                    scrub_error <= 1'b0;

                    if (scrub_all_command) begin
                        scrub_state <= SCRUB_CONFIG;
                        scrub_index <= 8'h0;
                        scrub_pass <= 2'd0;
                    end
                end

                SCRUB_CONFIG: begin
                    // FIXED: Scrub ALL config storage
                    if (scrub_index < 64) begin
                        // Multi-pass overwrite
                        case (scrub_pass)
                            2'd0: config_storage[scrub_index] <= 32'h00000000;
                            2'd1: config_storage[scrub_index] <= 32'hFFFFFFFF;
                            2'd2: config_storage[scrub_index] <= 32'h00000000;
                        endcase

                        if (scrub_pass == 2'd2) begin
                            scrub_index <= scrub_index + 1;
                            scrub_pass <= 2'd0;
                        end
                        else begin
                            scrub_pass <= scrub_pass + 1;
                        end
                    end
                    else begin
                        scrub_index <= 8'h0;
                        scrub_pass <= 2'd0;
                        scrub_state <= SCRUB_KEYS;
                    end
                end

                SCRUB_KEYS: begin
                    // FIXED: Scrub ALL key storage
                    if (scrub_index < 32) begin
                        case (scrub_pass)
                            2'd0: key_storage[scrub_index] <= 32'h00000000;
                            2'd1: key_storage[scrub_index] <= 32'hFFFFFFFF;
                            2'd2: key_storage[scrub_index] <= 32'h00000000;
                        endcase

                        if (scrub_pass == 2'd2) begin
                            scrub_index <= scrub_index + 1;
                            scrub_pass <= 2'd0;
                        end
                        else begin
                            scrub_pass <= scrub_pass + 1;
                        end
                    end
                    else begin
                        scrub_index <= 8'h0;
                        scrub_pass <= 2'd0;
                        scrub_state <= SCRUB_LOGS;
                    end
                end

                SCRUB_LOGS: begin
                    // FIXED: Scrub ALL log storage
                    if (scrub_index < 128) begin
                        case (scrub_pass)
                            2'd0: log_storage[scrub_index] <= 32'h00000000;
                            2'd1: log_storage[scrub_index] <= 32'hFFFFFFFF;
                            2'd2: log_storage[scrub_index] <= 32'h00000000;
                        endcase

                        if (scrub_pass == 2'd2) begin
                            scrub_index <= scrub_index + 1;
                            scrub_pass <= 2'd0;
                        end
                        else begin
                            scrub_pass <= scrub_pass + 1;
                        end
                    end
                    else begin
                        scrub_index <= 8'h0;
                        scrub_state <= VERIFY;
                    end
                end

                VERIFY: begin
                    // FIXED: Verify all storage is zeroed
                    if (scrub_index < 64 && config_storage[scrub_index] != 32'h0) begin
                        scrub_error <= 1'b1;
                    end
                    else if (scrub_index < 32 && key_storage[scrub_index] != 32'h0) begin
                        scrub_error <= 1'b1;
                    end
                    else if (scrub_index < 128 && log_storage[scrub_index] != 32'h0) begin
                        scrub_error <= 1'b1;
                    end

                    scrub_index <= scrub_index + 1;
                    if (scrub_index >= 128) begin
                        scrub_state <= DONE;
                    end
                end

                DONE: begin
                    scrub_complete <= 1'b1;
                    scrub_verified <= !scrub_error;
                    scrub_state <= IDLE;
                end
            endcase
        end
    end

endmodule

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CVE Examples

Data recovery from decommissioned devices has been demonstrated in numerous cases including:

• Medical devices with patient data
• Network equipment with credentials
• Enterprise storage with confidential data
• Point-of-sale terminals with payment information

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Related CWEs

• CWE-404: Improper Resource Shutdown or Release (parent)
• CWE-226: Sensitive Information in Resource Not Removed Before Reuse (related)
• CWE-459: Incomplete Cleanup (related)
• CAPEC-150: Collect Data from Common Resource Locations (attack pattern)
• CAPEC-675: Retrieve Data from Decommissioned Devices (attack pattern)

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References

1. MITRE Corporation. "CWE-1266: Improper Scrubbing of Sensitive Data from Decommissioned Device." https://cwe.mitre.org/data/definitions/1266.html
2. NIST SP 800-88. "Guidelines for Media Sanitization"
3. FIPS 140-3. "Zeroization Requirements"