Run static analysis (SAST) on the codebase looking for the unsafe pattern in the data flow.
CWE-1290 Base Incomplete
Incorrect Decoding of Security Identifiers
This vulnerability occurs when a hardware decoder incorrectly interprets security identifiers in bus transactions, allowing untrusted agents to gain unauthorized access to protected assets.
Definition
What is CWE-1290?
This vulnerability occurs when a hardware decoder incorrectly interprets security identifiers in bus transactions, allowing untrusted agents to gain unauthorized access to protected assets.
In a System-on-Chip (SoC), hardware components communicate through bus transactions that include security identifiers. These identifiers determine what actions an agent can perform—like reading, writing, or controlling a resource. A decoder maps these identifiers to specific access privileges. If this decoding logic is flawed, the system's fundamental access control can be bypassed.
The core risk arises when the decoder mistakenly maps an untrusted agent's identifier to a trusted one's privileges. This error effectively promotes an unauthorized agent's access level, letting it interact with assets it shouldn't. Developers must ensure the decoding logic is rigorously verified to prevent such privilege escalation in hardware security mechanisms.
Real-world impact
Real-world CVEs caused by CWE-1290
No public CVE references are linked to this CWE in MITRE's catalog yet.
How attackers exploit it
Step-by-step attacker path
- 1
Consider a system that has four bus masters and a decoder. The decoder is supposed to decode every bus transaction and assign a corresponding security identifier. The security identifier is used to determine accesses to the assets. The bus transaction that contains the security information is Bus_transaction [15:14], and the bits 15 through 14 contain the security identifier information. The table below provides bus masters as well as their security identifiers and trust assumptions: | Bus Master | Security Identifier Decoding | Trust Assumptions | | --- | --- | --- | | Master_0 | "00" | Untrusted | | Master_1 | "01" | Trusted | | Master_2 | "10" | Untrusted | | Master_3 | "11" | Untrusted | The assets are the AES-Key registers for encryption or decryption. The key is 128 bits implemented as a set of four 32-bit registers. The AES_KEY_ACCESS_POLICY is used to define which agents with a security identifier in the transaction can access the AES-key registers. The size of the security identifier is 4 bits (i.e., bit 3 through 0). Each bit in these 4 bits defines a security identifier. There are only 4 security identifiers that are allowed accesses to the AES-key registers. The number of the bit when set (i.e., "1") allows respective action from an agent whose identity matches the number of the bit. If clear (i.e., "0"), disallows the respective action to that corresponding agent. | Register | Field description | | --- | --- | | AES_ENC_DEC_KEY_0 | AES key [0:31] for encryption or decryption Default 0x00000000 | | AES_ENC_DEC_KEY_1 | AES key [32:63] for encryption or decryption Default 0x00000000 | | AES_ENC_DEC_KEY_2 | AES key [64:95] for encryption or decryption Default 0x00000000 | | AES_ENC_DEC_KEY_3 | AES key [96:127] for encryption or decryption Default 0x00000000 | | AES_KEY_ACCESS_POLCY | [31:4] Default 0x00000000 [3:0]-0x01 agent with Security Identified "1" has access to AES_ENC_DEC_KEY_0 through AES_ENC_DEC_KEY_3 registers |
- 2
The following Pseudo code outlines the process of checking the value of the Security Identifier within the AES_KEY_ACCESS_POLICY register:
- 3
Below is a decoder's Pseudo code that only checks for bit [14] of the bus transaction to determine what Security Identifier it must assign.
- 4
The security identifier is two bits, but the decoder code above only checks the value of one bit. Two Masters have their bit 0 set to "1" - Master_1 and Master_3. Master_1 is trusted, while Master_3 is not. The code above would therefore allow an untrusted agent, Master_3, access to the AES-Key registers in addition to intended trusted Master_1. The decoder should check for the entire size of the security identifier in the bus-transaction signal to assign a corresponding security identifier. The following is good Pseudo code:
Vulnerable code example
Vulnerable Other
Below is a decoder's Pseudo code that only checks for bit [14] of the bus transaction to determine what Security Identifier it must assign.
If (Bus_transaction[14] == "1")
Security_Identifier == "1"
Else
Security_Identifier == "0" Secure code example
Secure Other
The security identifier is two bits, but the decoder code above only checks the value of one bit. Two Masters have their bit 0 set to "1" - Master_1 and Master_3. Master_1 is trusted, while Master_3 is not. The code above would therefore allow an untrusted agent, Master_3, access to the AES-Key registers in addition to intended trusted Master_1. The decoder should check for the entire size of the security identifier in the bus-transaction signal to assign a corresponding security identifier. The following is good Pseudo code:
If (Bus_transaction[15:14] == "00")
Security_Identifier == "0"
If (Bus_transaction[15:14] == "01")
Security_Identifier == "1"
If (Bus_transaction[15:14] == "10")
Security_Identifier == "2"
If (Bus_transaction[15:14] == "11")
Security_Identifier == "3" What changed: the unsafe sink is replaced (or the input is validated/escaped) so the same payload no longer triggers the weakness.
Prevention checklist
How to prevent CWE-1290
- Architecture and Design Security identifier decoders must be reviewed for design consistency and common weaknesses.
- Implementation Access and programming flows must be tested in pre-silicon and post-silicon testing in order to check for this weakness.
Detection signals
How to detect CWE-1290
Run dynamic application security testing against the live endpoint.
Watch runtime logs for unusual exception traces, malformed input, or authorization bypass attempts.
Code review: flag any new code that handles input from this surface without using the validated framework helpers.
Plexicus auto-detects CWE-1290 and opens a fix PR in under 60 seconds.
Codex Remedium scans every commit, identifies this exact weakness, and ships a reviewer-ready pull request with the patch. No tickets. No hand-offs.
Frequently asked questions What is CWE-1290?
How serious is CWE-1290?
What languages or platforms are affected by CWE-1290?
How can I prevent CWE-1290?
How does Plexicus detect and fix CWE-1290?
Where can I learn more about CWE-1290?
Frequently asked questions
What is CWE-1290?
This vulnerability occurs when a hardware decoder incorrectly interprets security identifiers in bus transactions, allowing untrusted agents to gain unauthorized access to protected assets.
How serious is CWE-1290?
MITRE has not published a likelihood-of-exploit rating for this weakness. Treat it as medium-impact until your threat model proves otherwise.
What languages or platforms are affected by CWE-1290?
MITRE lists the following affected platforms: Not OS-Specific, Not Architecture-Specific, Bus/Interface Hardware, Not Technology-Specific.
How can I prevent CWE-1290?
Security identifier decoders must be reviewed for design consistency and common weaknesses. Access and programming flows must be tested in pre-silicon and post-silicon testing in order to check for this weakness.
How does Plexicus detect and fix CWE-1290?
Plexicus's SAST engine matches the data-flow signature for CWE-1290 on every commit. When a match is found, our Codex Remedium agent opens a fix PR with the corrected code, tests, and a one-line summary for the reviewer.
Where can I learn more about CWE-1290?
MITRE publishes the canonical definition at https://cwe.mitre.org/data/definitions/1290.html. You can also reference OWASP and NIST documentation for adjacent guidance.
Related weaknesses
Weaknesses related to CWE-1290
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