{"@ID": "337", "@Name": "Predictable Seed in Pseudo-Random Number Generator (PRNG)", "@Abstraction": "Variant", "@Structure": "Simple", "@Status": "Draft", "Description": "A Pseudo-Random Number Generator (PRNG) is initialized from a predictable seed, such as the process ID or system time.", "Extended_Description": "The use of predictable seeds significantly reduces the number of possible seeds that an attacker would need to test in order to predict which random numbers will be generated by the PRNG.", "Related_Weaknesses": {"Related_Weakness": {"@Nature": "ChildOf", "@CWE_ID": "335", "@View_ID": "1000", "@Ordinal": "Primary"}}, "Weakness_Ordinalities": {"Weakness_Ordinality": {"Ordinality": "Primary"}}, "Applicable_Platforms": {"Language": {"@Class": "Not Language-Specific", "@Prevalence": "Undetermined"}}, "Modes_Of_Introduction": {"Introduction": {"Phase": "Implementation", "Note": "REALIZATION: This weakness is caused during implementation of an architectural security tactic."}}, "Common_Consequences": {"Consequence": {"Scope": "Other", "Impact": "Varies by Context"}}, "Detection_Methods": {"Detection_Method": {"@Detection_Method_ID": "DM-14", "Method": "Automated Static Analysis", "Description": "Automated static analysis, commonly referred to as Static Application Security Testing (SAST), can find some instances of this weakness by analyzing source code (or binary/compiled code) without having to execute it. Typically, this is done by building a model of data flow and control flow, then searching for potentially-vulnerable patterns that connect \"sources\" (origins of input) with \"sinks\" (destinations where the data interacts with external components, a lower layer such as the OS, etc.)"}}, "Potential_Mitigations": {"Mitigation": [{"Description": "Use non-predictable inputs for seed generation."}, {"@Mitigation_ID": "MIT-2", "Phase": ["Architecture and Design", "Requirements"], "Strategy": "Libraries or Frameworks", "Description": "Use products or modules that conform to FIPS 140-2 [REF-267] to avoid obvious entropy problems, or use the more recent FIPS 140-3 [REF-1192] if possible."}, {"@Mitigation_ID": "MIT-50", "Phase": "Implementation", "Description": "Use a PRNG that periodically re-seeds itself using input from high-quality sources, such as hardware devices with high entropy. However, do not re-seed too frequently, or else the entropy source might block."}]}, "Demonstrative_Examples": {"Demonstrative_Example": {"@Demonstrative_Example_ID": "DX-102", "Intro_Text": "Both of these examples use a statistical PRNG seeded with the current value of the system clock to generate a random number:", "Example_Code": [{"@Nature": "Bad", "@Language": "Java", "xhtml:div": {"xhtml:br": null, "#text": "Random random = new Random(System.currentTimeMillis());int accountID = random.nextInt();"}}, {"@Nature": "Bad", "@Language": "C", "xhtml:div": {"xhtml:br": null, "#text": "srand(time());int randNum = rand();"}}], "Body_Text": "An attacker can easily predict the seed used by these PRNGs, and so also predict the stream of random numbers generated. Note these examples also exhibit CWE-338 (Use of Cryptographically Weak PRNG)."}}, "Observed_Examples": {"Observed_Example": [{"Reference": "CVE-2020-7010", "Description": "Cloud application on Kubernetes generates passwords using a weak random number generator based on deployment time.", "Link": "https://www.cve.org/CVERecord?id=CVE-2020-7010"}, {"Reference": "CVE-2019-11495", "Description": "server uses erlang:now() to seed the PRNG, which\n\t\t\t results in a small search space for potential random\n\t\t\t seeds", "Link": "https://www.cve.org/CVERecord?id=CVE-2019-11495"}, {"Reference": "CVE-2008-0166", "Description": "The removal of a couple lines of code caused Debian's OpenSSL Package to only use the current process ID for seeding a PRNG", "Link": "https://www.cve.org/CVERecord?id=CVE-2008-0166"}, {"Reference": "CVE-2016-10180", "Description": "Router's PIN generation is based on rand(time(0)) seeding.", "Link": "https://www.cve.org/CVERecord?id=CVE-2016-10180"}, {"Reference": "CVE-2018-9057", "Description": "cloud provider product uses a non-cryptographically secure PRNG and seeds it with the current time", "Link": "https://www.cve.org/CVERecord?id=CVE-2018-9057"}]}, "Taxonomy_Mappings": {"Taxonomy_Mapping": [{"@Taxonomy_Name": "PLOVER", "Entry_Name": "Predictable Seed in PRNG"}, {"@Taxonomy_Name": "The CERT Oracle Secure Coding Standard for Java (2011)", "Entry_ID": "MSC02-J", "Entry_Name": "Generate strong random numbers"}]}, "References": {"Reference": [{"@External_Reference_ID": "REF-267", "@Section": "Annex C, Approved Random Number Generators"}, {"@External_Reference_ID": "REF-1192"}, {"@External_Reference_ID": "REF-44", "@Section": "\"Sin 20: Weak Random Numbers.\" Page 299"}]}, "Mapping_Notes": {"Usage": "Allowed", "Rationale": "This CWE entry is at the Variant 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": "As of CWE 4.5, terminology related to randomness, entropy, and\n\t   predictability can vary widely. Within the developer and other\n\t   communities, \"randomness\" is used heavily. However, within\n\t   cryptography, \"entropy\" is distinct, typically implied as a\n\t   measurement. There are no commonly-used definitions, even within\n\t   standards documents and cryptography papers. Future versions of\n\t   CWE will attempt to define these terms and, if necessary,\n\t   distinguish between them in ways that are appropriate for\n\t   different communities but do not reduce the usability of CWE for\n\t   mapping, understanding, or other scenarios."}}, "Content_History": {"Submission": {"Submission_Name": "PLOVER", "Submission_Date": "2006-07-19", "Submission_Version": "Draft 3", "Submission_ReleaseDate": "2006-07-19"}, "Modification": [{"Modification_Name": "Sean Eidemiller", "Modification_Organization": "Cigital", "Modification_Date": "2008-07-01", "Modification_Version": "1.0", "Modification_ReleaseDate": "2008-09-09", "Modification_Comment": "added/updated demonstrative examples"}, {"Modification_Name": "Eric Dalci", "Modification_Organization": "Cigital", "Modification_Date": "2008-07-01", "Modification_Version": "1.0", "Modification_ReleaseDate": "2008-09-09", "Modification_Comment": "updated Time_of_Introduction"}, {"Modification_Name": "CWE Content Team", "Modification_Organization": "MITRE", "Modification_Date": "2008-09-08", "Modification_Version": "1.0", "Modification_ReleaseDate": "2008-09-09", "Modification_Comment": "updated Relationships, Taxonomy_Mappings"}, {"Modification_Name": "CWE Content Team", "Modification_Organization": "MITRE", "Modification_Date": "2009-03-10", "Modification_Version": "1.3", "Modification_ReleaseDate": "2009-03-10", "Modification_Comment": "updated Potential_Mitigations"}, {"Modification_Name": "CWE Content Team", "Modification_Organization": "MITRE", "Modification_Date": "2009-12-28", "Modification_Version": "1.7", "Modification_ReleaseDate": "2009-12-28", "Modification_Comment": "updated Potential_Mitigations"}, {"Modification_Name": "CWE Content Team", "Modification_Organization": "MITRE", "Modification_Date": "2010-06-21", "Modification_Version": "1.9", "Modification_ReleaseDate": "2010-06-21", "Modification_Comment": "updated Potential_Mitigations"}, {"Modification_Name": "CWE Content Team", "Modification_Organization": "MITRE", "Modification_Date": "2011-06-01", "Modification_Version": "1.13", "Modification_ReleaseDate": "2011-06-01", "Modification_Comment": "updated Common_Consequences, Relationships, Taxonomy_Mappings"}, {"Modification_Name": "CWE Content Team", "Modification_Organization": "MITRE", "Modification_Date": "2011-06-27", "Modification_Version": "2.0", "Modification_ReleaseDate": "2011-06-27", "Modification_Comment": "updated Common_Consequences"}, {"Modification_Name": "CWE Content Team", "Modification_Organization": "MITRE", "Modification_Date": "2011-09-13", "Modification_Version": "2.1", "Modification_ReleaseDate": "2011-09-13", "Modification_Comment": "updated Potential_Mitigations, References"}, {"Modification_Name": "CWE Content Team", "Modification_Organization": "MITRE", "Modification_Date": "2012-05-11", "Modification_Version": "2.2", "Modification_ReleaseDate": "2012-05-15", "Modification_Comment": "updated References, Relationships"}, {"Modification_Name": "CWE Content Team", "Modification_Organization": "MITRE", "Modification_Date": "2012-10-30", "Modification_Version": "2.3", "Modification_ReleaseDate": "2012-10-30", "Modification_Comment": "updated Demonstrative_Examples, Potential_Mitigations"}, {"Modification_Name": "CWE Content Team", "Modification_Organization": "MITRE", "Modification_Date": "2017-11-08", "Modification_Version": "3.0", "Modification_ReleaseDate": "2017-11-08", "Modification_Comment": "updated Applicable_Platforms, Demonstrative_Examples, Description, Modes_of_Introduction, Name, References, Relationships"}, {"Modification_Name": "CWE Content Team", "Modification_Organization": "MITRE", "Modification_Date": "2019-01-03", "Modification_Version": "3.2", "Modification_ReleaseDate": "2019-01-03", "Modification_Comment": "updated Relationships, Taxonomy_Mappings"}, {"Modification_Name": "CWE Content Team", "Modification_Organization": "MITRE", "Modification_Date": "2019-06-20", "Modification_Version": "3.3", "Modification_ReleaseDate": "2019-06-20", "Modification_Comment": "updated Type"}, {"Modification_Name": "CWE Content Team", "Modification_Organization": "MITRE", "Modification_Date": "2020-02-24", "Modification_Version": "4.0", "Modification_ReleaseDate": "2020-02-24", "Modification_Comment": "updated Description, Relationships"}, {"Modification_Name": "CWE Content Team", "Modification_Organization": "MITRE", "Modification_Date": "2021-07-20", "Modification_Version": "4.5", "Modification_ReleaseDate": "2021-07-20", "Modification_Comment": "updated Maintenance_Notes, Observed_Examples, Potential_Mitigations, References"}, {"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 Relationships"}, {"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 Observed_Examples"}, {"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 References, Relationships, Time_of_Introduction"}, {"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, Relationships"}, {"Modification_Name": "CWE Content Team", "Modification_Organization": "MITRE", "Modification_Date": "2025-09-09", "Modification_Version": "4.18", "Modification_ReleaseDate": "2025-09-09", "Modification_Comment": "updated References"}, {"Modification_Name": "CWE Content Team", "Modification_Organization": "MITRE", "Modification_Date": "2025-12-11", "Modification_Version": "4.19", "Modification_ReleaseDate": "2025-12-11", "Modification_Comment": "updated Detection_Factors, Relationships, Weakness_Ordinalities"}], "Previous_Entry_Name": {"@Date": "2017-11-08", "#text": "Predictable Seed in PRNG"}}}