CWE-1290: Incorrect Decoding of Security Identifiers

Extended Description

In a System-On-Chip (SoC), various integrated circuits and hardware engines generate transactions such as to access (reads/writes) assets or perform certain actions (e.g., reset, fetch, compute, etc.). Among various types of message information, a typical transaction is comprised of source identity (to identify the originator of the transaction) and a destination identity (to route the transaction to the respective entity). Sometimes the transactions are qualified with a security identifier. The security identifier helps the destination agent decide on the set of allowed actions (e.g., access an asset for read and writes). A decoder decodes the bus transactions to map security identifiers into necessary access-controls/protections. A common weakness that can exist in this scenario is incorrect decoding because an untrusted agent's security identifier is decoded into a trusted agent's security identifier. Thus, an untrusted agent previously without access to an asset can now gain access to the asset.

Code Examples & CVEs

Demonstrative Examples

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 MasterSecurity Identifier DecodingTrust 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. RegisterField description AES_ENC_DEC_KEY_0AES key [0:31] for encryption or decryptionDefault 0x00000000 AES_ENC_DEC_KEY_1AES key [32:63] for encryption or decryptionDefault 0x00000000 AES_ENC_DEC_KEY_2AES key [64:95] for encryption or decryptionDefault 0x00000000 AES_ENC_DEC_KEY_3AES key [96:127] for encryption or decryptionDefault 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

The following Pseudo code outlines the process of checking the value of the Security Identifier within the AES_KEY_ACCESS_POLICY register:

BadOther

If (Bus_transaction[14] == "1")                                                                                            Security_Identifier == "1"                                                                                           Else                                                                                           Security_Identifier == "0"

The following Pseudo code outlines the process of checking the value of the Security Identifier within the AES_KEY_ACCESS_POLICY register:

GoodOther

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"

Source-backed guidance

Additional facts reviewed against primary or authoritative security sources.

Verify controls for CWE-1290 with SSDF evidence

Use NIST SSDF verification and vulnerability-response practices to detect CWE-1290, Incorrect Decoding of Security Identifiers, throughout the product lifecycle. Derive review questions, static or dynamic checks, and negative tests from the CWE's causal behavior; define the components and lifecycle stages each check covers; and retain findings with enough evidence to distinguish the root cause from symptoms and impacts. Track escapes and false negatives, then improve the verification plan after every confirmed occurrence.

NIST SP 800-218 Secure Software Development Framework — National Institute of Standards and Technology

Address Incorrect Decoding of Security Identifiers during Architecture and Design

MITRE associates mitigation with Architecture and Design, and Implementation; recorded impacts include Modify Memory, Read Memory, DoS: Resource Consumption (Other), Execute Unauthorized Code or Commands, and Gain Privileges or Assume Identity; related weaknesses include CWE-284, and CWE-1294. Use these source-defined anchors to turn CWE-1290 into implementation, review, and verification checks for the affected component.

CWE-1290: Incorrect Decoding of Security Identifiers — MITRE CWE

Triage CWE-1290 against known exploitation evidence

Use CISA's Known Exploited Vulnerabilities catalog to test whether a vulnerability mapped to CWE-1290, Incorrect Decoding of Security Identifiers, has evidence of exploitation in the wild. Confirm the CVE-to-CWE root-cause mapping independently before attaching the example, then capture the affected product, required action, and remediation deadline. A missing KEV match is not evidence that the weakness is unexploited, and a KEV entry must not be generalized to every occurrence of this CWE.

Known Exploited Vulnerabilities Catalog — Cybersecurity and Infrastructure Security Agency

Apply precise root-cause mapping to CWE-1290

Apply MITRE's full root-cause mapping guidance when using CWE-1290, Incorrect Decoding of Security Identifiers. Separate weakness language from attacker prerequisites and technical impact, check the entry's abstraction and vulnerability-mapping notes, and prefer the most specific Base or Variant supported by the evidence. Record the rejected alternatives and require an independent review before the mapping is used for remediation trends or program metrics.

CVE to CWE Root Cause Mapping Guidance — MITRE CWE

Validate CWE-1290 with root-cause mapping checks

Apply MITRE's root-cause mapping quick tips to CWE-1290, Incorrect Decoding of Security Identifiers. Confirm the finding describes the causal weakness rather than an impact or attack pattern, compare the abstraction and mapping notes with plausible alternatives, and have a second reviewer challenge the selection. Preserve the evidence and reasoning so recurring defects can be measured against one consistent identifier.

CVE to CWE Root Cause Mapping Quick Tips — MITRE CWE

Frequently Asked Questions

What is CWE-1290: Incorrect Decoding of Security Identifiers?+

CWE-1290: Incorrect Decoding of Security Identifiers is a Common Weakness Enumeration (CWE) entry maintained by MITRE. The product implements a decoding mechanism to decode certain bus-transaction signals to security identifiers. If the decoding is implemented incorrectly, then untrusted agents can now gain unauthorized access to the asset. In a System-On-Chip (SoC), various integrated circuits and hardware engines generate transactions such as to access (reads/writes) assets or perform certain actions (e.g., reset, fetch, compute, etc.). Among various types of message information, a typical transaction is comprised of source identity (to identify the originator of the transaction) and a destination identity (to route the transaction to the respective entity). Sometimes the transactions are qualified with a security identifier. The security identifier helps the destination agent decide on the set of allowed actions (e.g., access an asset for read and writes). A decoder decodes the bus transactions to map security identifiers into necessary access-controls/protections. A common weakness that can exist in this scenario is incorrect decoding because an untrusted agent's security identifier is decoded into a trusted agent's security identifier. Thus, an untrusted agent previously without access to an asset can now gain access to the asset.

What are the security consequences of Incorrect Decoding of Security Identifiers?+

If exploited, CWE-1290 (Incorrect Decoding of Security Identifiers) it can compromise Confidentiality, Integrity, Availability and Access Control, leading to outcomes such as Modify Memory, Read Memory, DoS: Resource Consumption (Other), Execute Unauthorized Code or Commands, Gain Privileges or Assume Identity and Quality Degradation.

How do you prevent or mitigate Incorrect Decoding of Security Identifiers?+

Recommended mitigations for CWE-1290 include: 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.

Which programming languages are affected by Incorrect Decoding of Security Identifiers?+

CWE-1290 commonly affects Not Language-Specific. Note that weaknesses are often language-agnostic patterns, so secure coding practices apply broadly.

What is the difference between a CWE and a CVE?+

A CWE (Common Weakness Enumeration) like CWE-1290 describes a category of software weakness — the underlying flaw type. A CVE (Common Vulnerabilities and Exposures) identifies a specific, real-world vulnerability in a particular product. In short, a CWE is the kind of mistake, and a CVE is an instance of that mistake being found in software.

CWE-1290: Incorrect Decoding of Security Identifiers

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