Automated testing can verify that RoT components are immutable.
CWE-1326 Base Borrador
Missing Immutable Root of Trust in Hardware
This vulnerability occurs when a hardware chip lacks a permanent, unchangeable root of trust. Without this immutable foundation, attackers can bypass secure boot protections and run unauthorized or…
Definición
What is CWE-1326?
This vulnerability occurs when a hardware chip lacks a permanent, unchangeable root of trust. Without this immutable foundation, attackers can bypass secure boot protections and run unauthorized or malicious code during the system startup process.
Secure boot in a System-on-Chip (SoC) relies on verifying signed boot code using a trusted key. The chip must also check critical hardware settings, like a 'secure boot enabled' fuse. Together, this code and configuration data form the Root of Trust (RoT), which is the absolute starting point for all security. If an attacker can modify this RoT, they can compromise the entire boot chain.
To prevent this, the RoT must be stored in immutable memory, such as locked fuses or one-time-programmable (OTP) memory, after initial provisioning. This ensures the foundational security data cannot be rewritten. It's important to distinguish this from components like ROM, which should support secure, authenticated update mechanisms for authorized patches in the field, while the core RoT itself remains permanently fixed.
Impacto en el mundo real
Real-world CVEs caused by CWE-1326
Todavía no hay CVEs públicos enlazados a esta CWE en el catálogo de MITRE.
Cómo lo explotan los atacantes
Ruta del atacante paso a paso
- 1
The RoT is stored in memory. This memory can be modified by an adversary. For example, if an SoC implements "Secure Boot" by storing the boot code in an off-chip/on-chip flash, the contents of the flash can be modified by using a flash programmer. Similarly, if the boot code is stored in ROM (Read-Only Memory) but the public key or the hash of the public key (used to enable "Secure Boot") is stored in Flash or a memory that is susceptible to modifications or writes, the implementation is vulnerable.
- 2
In general, if the boot code, key materials and data that enable "Secure Boot" are all mutable, the implementation is vulnerable.
- 3
Good architecture defines RoT as immutable in hardware. One of the best ways to achieve immutability is to store boot code, public key or hash of the public key and other relevant data in Read-Only Memory (ROM) or One-Time Programmable (OTP) memory that prevents further programming or writes.
- 4
The example code below is a snippet from the bootrom of the HACK@DAC'19 buggy OpenPiton SoC [REF-1348]. The contents of the bootrom are critical in implementing the hardware root of trust.
- 5
It performs security-critical functions such as defining the system's device tree, validating the hardware cryptographic accelerators in the system, etc. Hence, write access to bootrom should be strictly limited to authorized users or removed completely so that bootrom is immutable. In this example (see the vulnerable code source), the boot instructions are stored in bootrom memory, mem. This memory can be read using the read address, addr_i, but write access should be restricted or removed.
Ejemplo de código vulnerable
Vulnerable Verilog
It performs security-critical functions such as defining the system's device tree, validating the hardware cryptographic accelerators in the system, etc. Hence, write access to bootrom should be strictly limited to authorized users or removed completely so that bootrom is immutable. In this example (see the vulnerable code source), the boot instructions are stored in bootrom memory, mem. This memory can be read using the read address, addr_i, but write access should be restricted or removed.
...
always_ff @(posedge clk_i) begin
if (req_i) begin
if (!we_i) begin
raddr_q <= addr_i[$clog2(RomSize)-1+3:3];
end else begin
```
mem[addr_i[$clog2(RomSize)-1+3:3]] <= wdata_i;** end end end ...
```
// this prevents spurious Xes from propagating into the speculative fetch stage of the core
assign rdata_o = (raddr_q < RomSize) ? mem[raddr_q] : '0;
... Ejemplo de código seguro
Secure Verilog
To mitigate this issue, remove the write access to bootrom memory. [REF-1349]
...
always_ff @(posedge clk_i) begin
```
if (req_i) begin**
```
raddr_q <= addr_i[$clog2(RomSize)-1+3:3];
end
end
...
// this prevents spurious Xes from propagating into the speculative fetch stage of the core
assign rdata_o = (raddr_q < RomSize) ? mem[raddr_q] : '0;
... What changed: the unsafe sink is replaced (or the input is validated/escaped) so the same payload no longer triggers the weakness.
Lista de prevención
How to prevent CWE-1326
- Architecture and Design When architecting the system, the RoT should be designated for storage in a memory that does not allow further programming/writes.
- Implementation During implementation and test, the RoT memory location should be demonstrated to not allow further programming/writes.
Señales de detección
How to detect CWE-1326
Root of trust elements and memory should be part of architecture and design reviews.
Plexicus detecta automáticamente CWE-1326 y abre un PR de corrección en menos de 60 segundos.
Codex Remedium escanea cada commit, identifica esta debilidad concreta y entrega un pull request listo para revisión con el parche. Sin tickets. Sin traspasos.
Preguntas frecuentes ¿Qué es CWE-1326?
¿Qué gravedad tiene CWE-1326?
¿Qué lenguajes o plataformas se ven afectados por CWE-1326?
¿Cómo puedo prevenir CWE-1326?
¿Cómo detecta y corrige Plexicus CWE-1326?
¿Dónde puedo aprender más sobre CWE-1326?
Frequently asked questions
¿Qué es CWE-1326?
This vulnerability occurs when a hardware chip lacks a permanent, unchangeable root of trust. Without this immutable foundation, attackers can bypass secure boot protections and run unauthorized or malicious code during the system startup process.
¿Qué gravedad tiene CWE-1326?
MITRE no ha publicado una calificación de probabilidad de explotación para esta debilidad. Trátala como de impacto medio hasta que tu modelo de amenazas demuestre lo contrario.
¿Qué lenguajes o plataformas se ven afectados por CWE-1326?
MITRE lists the following affected platforms: Not OS-Specific, Not Architecture-Specific, Security Hardware, Not Technology-Specific.
¿Cómo puedo prevenir CWE-1326?
When architecting the system, the RoT should be designated for storage in a memory that does not allow further programming/writes. During implementation and test, the RoT memory location should be demonstrated to not allow further programming/writes.
¿Cómo detecta y corrige Plexicus CWE-1326?
El motor SAST de Plexicus detecta la firma de flujo de datos para CWE-1326 en cada commit. Cuando hay coincidencia, nuestro agente Codex Remedium abre un PR de corrección con el código corregido, las pruebas y un resumen de una línea para el revisor.
¿Dónde puedo aprender más sobre CWE-1326?
MITRE publica la definición canónica en https://cwe.mitre.org/data/definitions/1326.html. También puedes consultar la documentación de OWASP y NIST para guías relacionadas.
Debilidades relacionadas
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Recursos
Further reading
- MITRE — CWE-1326 oficial https://cwe.mitre.org/data/definitions/1326.html
- TCG Roots of Trust Specification https://trustedcomputinggroup.org/wp-content/uploads/TCG_Roots_of_Trust_Specification_v0p20_PUBLIC_REVIEW.pdf
- Root of Trust Definitions and Requirements https://globalplatform.org/wp-content/uploads/2018/06/GP_RoT_Definitions_and_Requirements_v1.0.1_PublicRelease_CC.pdf
- bootrom.sv https://github.com/HACK-EVENT/hackatdac19/blob/619e9fb0ef32ee1e01ad76b8732a156572c65700/bootrom/bootrom.sv#L263C19-L263C19
- bootrom.sv https://github.com/HACK-EVENT/hackatdac19/blob/ba6abf58586b2bf4401e9f4d46e3f084c664ff88/bootrom/bootrom.sv#L259C9-L259C9
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