CWEweakness

CWE-331 Insufficient Entropy

Official page ↗
Abstraction
Base
Structure
Simple
Status
Draft
Languages
Not Language-Specific
CWE version
5.0

Description

The product uses an algorithm or scheme that produces insufficient entropy, leaving patterns or clusters of values that are more likely to occur than others.

Common consequences

• Access Control, Other: Bypass Protection Mechanism, Other — An attacker could guess the random numbers generated and could gain unauthorized access to a system if the random numbers are used for authentication and authorization.

Potential mitigations

• [Implementation] Determine the necessary entropy to adequately provide for randomness and predictability. This can be achieved by increasing the number of bits of objects such as keys and seeds.

Detection methods

• Automated Static Analysis: 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.)

Observed examples

• CVE-2001-0950: Insufficiently random data used to generate session tokens using C rand(). Also, for certificate/key generation, uses a source that does not block when entropy is low. • CVE-2008-2108: Chain: insufficient precision (CWE-1339) in random-number generator causes some zero bits to be reliably generated, reducing the amount of entropy (CWE-331)

Related

Attack pattern · CAPEC (1)

  • CAPEC-59 Session Credential Falsification through Prediction attack pattern

Observed example · CVE (2)

  • CVE-2008-2108 The GENERATE_SEED macro in PHP 4.x before 4.4.8 and 5.x before 5.2.5, when running on 64-bit systems, performs a multiplication that… vulnerability
  • CVE-2001-0950 ValiCert Enterprise Validation Authority (EVA) Administration Server 3.3 through 4.2.1 uses insufficiently random data to (1) generate… vulnerability

Child of · CWE (1)

  • CWE-330 Use of Insufficiently Random Values weakness

Referenced by CAPEC · weakness (1)

  • CAPEC-59 Session Credential Falsification through Prediction attack pattern

Referenced by CVE · weakness (149)

  • CVE-2026-92209 NoMachine Redis Improper Authentication Local Privilege Escalation Vulnerability. vulnerability
  • CVE-2026-112041 A vulnerability was identified in diem-project diem up to 116974edfb9a5b8bd69cb13586dc62bcdbb485ad. vulnerability
  • CVE-2026-13639 An insufficient entropy vulnerability in login logic in Synology DiskStation Manager (DSM) before 7.2.1-69057-12, 7.2.2-72806-9,… vulnerability
  • CVE-2026-90562 LangBot before 4.10.11 generates password recovery keys with only 24 bits of entropy and applies no rate limiting to the unauthenticated… vulnerability
  • CVE-2026-80171 Dell SCG 5.0 Appliance versions prior to 5.36.00.16 and Dell SCG 5.0 Application versions prior to 5.36.00.00, contains an Insufficient… vulnerability
  • CVE-2026-62646 A vulnerability has been identified in Reyrolle 7SR5 (All versions < V2.70). vulnerability
  • CVE-2026-27490 Combodo iTop is a web based IT service management tool. vulnerability
  • CVE-2026-4936 IBM PowerVM Hypervisor Platform KeyStore (PKS) and virtual TPM FW1110.00 through FW1110.20, FW1060.00 through FW1060.71, and FW950.00… vulnerability
  • CVE-2026-4937 IBM PowerVM Hypervisor FW1110.00 through FW1110.20, FW1060.00 through FW1060.71, and FW950.00 through FW950.H2 could allow a local attacker… vulnerability
  • CVE-2026-19906 A weakness has been identified in pkp pkp-lib 3.3.0/3.4.0/3.5.0. vulnerability
  • CVE-2026-19748 A security vulnerability has been detected in Tenda CH7, CH7G, CH10, CP3, CP3 Pro, CP7, TC3B14C, TC3B15C, TC3T14C and TC3T15C up to… vulnerability
  • CVE-2026-71851 crypto-js is a JavaScript library of crypto standards. vulnerability
  • CVE-2025-15629 A cryptographic weakness exists in the Omada adoption protocol where session encryption keys used to protect communications between… vulnerability
  • CVE-2026-38447 osTicket 1.18.3 generates API keys using a predictable construction based on MD5 hashing. vulnerability
  • CVE-2026-4932 IBM PowerVM Hypervisor FW1110.00 through FW1110.20, and FW1060.00 through FW1060.71 could allow an attacker with physical access to the… vulnerability
  • CVE-2026-11403 A vulnerability in Sonatype Nexus Repository Manager's format-specific API key generation may allow a remote attacker to gain unauthorized… vulnerability
  • CVE-2026-13199 EEPROM firmware on Raspberry Pi 5 and Compute Module 5 devices produced non-random KASLR and RNG seed values. vulnerability
  • CVE-2026-4930 SYMCRYPTO is the SiXG301's host side hardware engine accessed by PSA crypto library that accelerates symmetric cryptographic operations… vulnerability
  • CVE-2026-46473 Authen::TOTP versions before 0.1.1 for Perl generate secrets using rand. vulnerability
  • CVE-2025-14972 * Countermeasures for DPA within SYMCRYPTO engine on SixG301xxx devices are not sufficiently random and will eventually repeat. vulnerability
  • CVE-2026-42155 Magento Long Term Support (LTS) is an unofficial, community-driven project provides an alternative to the Magento Community Edition… vulnerability
  • CVE-2026-46474 Trog::TOTP versions before 1.006 for Perl generate secrets using rand. vulnerability
  • CVE-2026-8700 Crypt::DSA versions before 1.20 for Perl generate seeds using rand. vulnerability
  • CVE-2026-4827 CWE‑331: Insufficient Entropy vulnerability exists that could lead to unauthorized access when an attacker on the network can exploit… vulnerability
  • CVE-2026-7210 `xml.parsers.expat` and `xml.etree.ElementTree` use insufficient entropy for Expat hash-flooding protection, which allows a crafted XML… vulnerability
  • CVE-2026-2336 A privilege escalation vulnerability in Microchip IStaX allows an authenticated low-privileged user to recover a shared per-device cookie… vulnerability
  • CVE-2026-41080 libexpat before 2.8.0 uses insufficient entropy, and thus hash flooding can occur via a crafted XML document. vulnerability
  • CVE-2026-34236 Auth0-PHP is a PHP SDK for Auth0 Authentication and Management APIs. vulnerability
  • CVE-2026-2878 In Progress® Telerik® UI for AJAX, versions prior to 2026.1.225, an insufficient entropy vulnerability exists in RadAsyncUpload, where a… vulnerability
  • CVE-2025-0577 An insufficient entropy vulnerability was found in glibc. vulnerability
Show all 149 ›

Referenced by CWE · child of (2)

  • CWE-332 Insufficient Entropy in PRNG weakness
  • CWE-333 Improper Handling of Insufficient Entropy in TRNG weakness

Referenced by CWE · has member (1)

Referenced by OWASP · mapped cwe (2)

  • A04:2025 Cryptographic Failures Top 10 2025
  • A02:2021 Cryptographic Failures Top 10 2021