{"@ID": "1271", "@Name": "Uninitialized Value on Reset for Registers Holding Security Settings", "@Abstraction": "Base", "@Structure": "Simple", "@Status": "Incomplete", "Description": "Security-critical logic is not set to a known value on reset.", "Related_Weaknesses": {"Related_Weakness": {"@Nature": "ChildOf", "@CWE_ID": "909", "@View_ID": "1000", "@Ordinal": "Primary"}}, "Weakness_Ordinalities": {"Weakness_Ordinality": {"Ordinality": "Primary"}}, "Applicable_Platforms": {"Language": {"@Class": "Not Language-Specific", "@Prevalence": "Undetermined"}, "Operating_System": {"@Class": "Not OS-Specific", "@Prevalence": "Undetermined"}, "Architecture": {"@Class": "Not Architecture-Specific", "@Prevalence": "Undetermined"}, "Technology": {"@Class": "Not Technology-Specific", "@Prevalence": "Undetermined"}}, "Modes_Of_Introduction": {"Introduction": {"Phase": "Implementation"}}, "Common_Consequences": {"Consequence": {"Scope": ["Access Control", "Authentication", "Authorization"], "Impact": "Varies by Context", "Note": "When the device is first brought out of reset, the state of registers will be indeterminate if they have not been initialized by the logic. Before the registers are initialized, there will be a window during which the device is in an insecure state and may be vulnerable to attack."}}, "Potential_Mitigations": {"Mitigation": [{"Phase": "Implementation", "Description": "Design checks should be performed to identify any uninitialized flip-flops used for security-critical functions."}, {"Phase": "Architecture and Design", "Description": "All registers holding security-critical information should be set to a specific value on reset."}]}, "Demonstrative_Examples": {"Demonstrative_Example": {"Intro_Text": "Shown below is a positive clock edge triggered flip-flop used to implement a lock bit for test and debug interface. When the circuit is first brought out of reset, the state of the flip-flop will be unknown until the enable input and D-input signals update the flip-flop state. In this example, an attacker can reset the device until the test and debug interface is unlocked and access the test interface until the lock signal is driven to a known state by the logic.", "Example_Code": [{"@Nature": "Bad", "@Language": "Verilog", "xhtml:br": null, "xhtml:div": {"@style": "margin-left:1em;", "xhtml:br": null, "#text": "if (en) lock_jtag <= d;"}, "#text": "always @(posedge clk) begin\n\t\t\t\t\t    \n\t\t\t\t\t    end", "#text_blocks": ["always @(posedge clk) begin", "if (en) lock_jtag <= d;", "end"]}, {"@Nature": "Good", "@Language": "Verilog", "xhtml:br": [null, null], "xhtml:div": {"@style": "margin-left:1em;", "xhtml:br": [null, null], "#text": "if (~reset) lock_jtag <= 0;\n\t\t\t\t\t    else if (en) lock_jtag <= d;"}, "#text": "always @(posedge clk) begin\n\t\t\t\t\t  \n\t\t\t\t\t  end", "#text_blocks": ["always @(posedge clk) begin", "if (~reset) lock_jtag <= 0;", "else if (en) lock_jtag <= d;", "end"]}], "Body_Text": "The flip-flop can be set to a known value (0 or 1) on reset, but requires that the logic explicitly update the output of the flip-flop if the reset signal is active."}}, "Related_Attack_Patterns": {"Related_Attack_Pattern": {"@CAPEC_ID": "74"}}, "Mapping_Notes": {"Usage": "Allowed", "Rationale": "This CWE entry is at the Base level of abstraction, which is a preferred level of abstraction for mapping to the root causes of vulnerabilities.", "Comments": "Carefully read both the name and description to ensure that this mapping is an appropriate fit. Do not try to 'force' a mapping to a lower-level Base/Variant simply to comply with this preferred level of abstraction.", "Reasons": {"Reason": {"@Type": "Acceptable-Use"}}}, "Notes": {"Note": {"@Type": "Maintenance", "#text": "This entry is still under development and will continue to see updates and content improvements."}}, "Content_History": {"Submission": {"Submission_Name": "Nicole Fern", "Submission_Organization": "Cycuity (originally submitted as Tortuga Logic)", "Submission_Date": "2020-05-15", "Submission_Version": "4.1", "Submission_ReleaseDate": "2020-02-24"}, "Modification": [{"Modification_Name": "CWE Content Team", "Modification_Organization": "MITRE", "Modification_Date": "2020-08-20", "Modification_Version": "4.2", "Modification_ReleaseDate": "2020-08-20", "Modification_Comment": "updated Common_Consequences, Demonstrative_Examples, Description, Modes_of_Introduction, Name, Potential_Mitigations, Related_Attack_Patterns, Relationships"}, {"Modification_Name": "CWE Content Team", "Modification_Organization": "MITRE", "Modification_Date": "2021-03-15", "Modification_Version": "4.4", "Modification_ReleaseDate": "2021-03-15", "Modification_Comment": "updated Name, Type"}, {"Modification_Name": "CWE Content Team", "Modification_Organization": "MITRE", "Modification_Date": "2021-10-28", "Modification_Version": "4.6", "Modification_ReleaseDate": "2021-10-28", "Modification_Comment": "updated Weakness_Ordinalities"}, {"Modification_Name": "CWE Content Team", "Modification_Organization": "MITRE", "Modification_Date": "2022-10-13", "Modification_Version": "4.9", "Modification_ReleaseDate": "2022-10-13", "Modification_Comment": "updated Demonstrative_Examples"}, {"Modification_Name": "CWE Content Team", "Modification_Organization": "MITRE", "Modification_Date": "2023-01-31", "Modification_Version": "4.10", "Modification_ReleaseDate": "2023-01-31", "Modification_Comment": "updated Relationships"}, {"Modification_Name": "CWE Content Team", "Modification_Organization": "MITRE", "Modification_Date": "2023-04-27", "Modification_Version": "4.11", "Modification_ReleaseDate": "2023-04-27", "Modification_Comment": "updated Relationships"}, {"Modification_Name": "CWE Content Team", "Modification_Organization": "MITRE", "Modification_Date": "2023-06-29", "Modification_Version": "4.12", "Modification_ReleaseDate": "2023-06-29", "Modification_Comment": "updated Mapping_Notes"}, {"Modification_Name": "CWE Content Team", "Modification_Organization": "MITRE", "Modification_Date": "2026-10-28", "Modification_Version": "5.0", "Modification_ReleaseDate": "2026-10-28", "Modification_Comment": "updated Common_Consequences, Description"}], "Previous_Entry_Name": [{"@Date": "2020-08-20", "#text": "Missing Known Value on Reset for Registers Holding Security Settings"}, {"@Date": "2021-03-15", "#text": "Unitialized Value on Reset for Registers Holding Security Settings"}]}, "entry_type": "Weakness"}