CWEweakness

CWE-342 Predictable Exact Value from Previous Values

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

Description

An exact value or random number can be precisely predicted by observing previous values.

Common consequences

• Other: Varies by Context

Potential mitigations

• Increase the entropy used to seed a PRNG. • [Architecture and Design, Requirements] Use products or modules that conform to FIPS 140-2 [REF-267] to avoid obvious entropy problems. Consult FIPS 140-2 Annex C ("Approved Random Number Generators"). • [Implementation] 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.

Observed examples

• CVE-2002-1463: Firewall generates easily predictable initial sequence numbers (ISN), which allows remote attackers to spoof connections. • CVE-1999-0074: Listening TCP ports are sequentially allocated, allowing spoofing attacks. • CVE-1999-0077: Predictable TCP sequence numbers allow spoofing. • CVE-2000-0335: DNS resolver uses predictable IDs, allowing a local user to spoof DNS query results.

Related

Observed example · CVE (4)

  • CVE-2002-1463 Symantec Raptor Firewall 6.5 and 6.5.3, Enterprise Firewall 6.5.2 and 7.0, VelociRaptor Models 500/700/1000 and 1100/1200/1300, and Gateway… vulnerability
  • CVE-2000-0335 The resolver in glibc 2.1.3 uses predictable IDs, which allows a local attacker to spoof DNS query results. vulnerability
  • CVE-1999-0074 Listening TCP ports are sequentially allocated, allowing spoofing attacks. vulnerability
  • CVE-1999-0077 Predictable TCP sequence numbers allow spoofing. vulnerability

Child of · CWE (1)

  • CWE-340 Generation of Predictable Numbers or Identifiers weakness

Referenced by CVE · weakness (7)

  • CVE-2026-88778 Predictable exact value from previous values vulnerability in Citrix NetScaler ADC and Citrix NetScaler Gateway. vulnerability
  • CVE-2023-3373 Predictable Exact Value from Previous Values vulnerability in Mitsubishi Electric Corporation GOT2000 Series GT21 model versions 01.49.000… vulnerability
  • CVE-2022-29930 SHA1 implementation in JetBrains Ktor Native 2.0.0 was returning the same value. vulnerability
  • CVE-2022-27577 The vulnerability in the MSC800 in all versions before 4.15 allows for an attacker to predict the TCP initial sequence number. vulnerability
  • CVE-2020-28388 A vulnerability has been identified in APOGEE PXC Compact (BACnet) (All versions < V3.5.5), APOGEE PXC Compact (P2 Ethernet) (All versions… vulnerability
  • CVE-2020-16226 Multiple Mitsubishi Electric products are vulnerable to impersonations of a legitimate device by a malicious actor, which may allow an… vulnerability
  • CVE-2014-9196 Eaton Cooper Power Systems ProView 4.0 and 5.0 before 5.0 11 on Form 6 controls and Idea and IdeaPLUS relays generates TCP initial sequence… vulnerability

Referenced by OWASP · mapped cwe (1)

  • A04:2025 Cryptographic Failures Top 10 2025