CWE

Predictable from Observable State

ID: 341		Date: (C)2012-05-14   (M)2022-10-10
Type: weakness		Status: DRAFT
Abstraction Type: Base

Description

A number or object is predictable based on observations that the attacker can make about the state of the system or network, such as time, process ID, etc.

Applicable Platforms
Language Class: All

Time Of Introduction

• Architecture and Design
• Implementation

Common Consequences

Scope	Technical Impact	Notes
Other	Varies by context	This weakness could be exploited by an attacker in a number ways depending on the context. If a predictable number is used to generate IDs or keys that are used within protection mechanisms, then an attacker could gain unauthorized access to the system. If predictable filenames are used for storing sensitive information, then an attacker might gain access to the system and may be able to gain access to the information in the file.

Detection Methods
None

Potential Mitigations

Phase	Strategy	Description	Effectiveness	Notes
Implementation		Increase the entropy used to seed a PRNG.
Architecture and Design Requirements	Libraries or Frameworks	Use products or modules that conform to FIPS 140-2 [R.341.1] 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.

Relationships

Related CWE	Type	View	Chain
CWE-341 ChildOf CWE-905	Category	CWE-888

Demonstrative Examples   (Details)

1. This code generates a unique random identifier for a user's session. (Demonstrative Example Id DX-45)

Observed Examples

1. CVE-2002-0389 : Mail server stores private mail messages with predictable filenames in a world-executable directory, which allows local users to read private mailing list archives.
2. CVE-2001-1141 : PRNG allows attackers to use the output of small PRNG requests to determine the internal state information, which could be used by attackers to predict future pseudo-random numbers.
3. CVE-2000-0335 : DNS resolver library uses predictable IDs, which allows a local attacker to spoof DNS query results.
4. CVE-2005-1636 : MFV. predictable filename and insecure permissions allows file modification to execute SQL queries.

For more examples, refer to CVE relations in the bottom box.

White Box Definitions
None

Black Box Definitions
None

Taxynomy Mappings

Taxynomy	Id	Name	Fit
PLOVER		Predictable from Observable State

References:

1. Information Technology Laboratory, National Institute of Standards and Technology .SECURITY REQUIREMENTS FOR CRYPTOGRAPHIC MODULES. 2001-05-25.
2. Michael Howard David LeBlanc John Viega .24 Deadly Sins of Software Security. McGraw-Hill. Section:'"Sin 20: Weak Random Numbers." Page 299'. Published on 2010.