COMMON ATTACK PATTERN ENUMERATION AND CLASSIFICATIONLive MITRE record

CAPEC-59

Session Credential Falsification through Prediction

This attack targets predictable session ID in order to gain privileges. The attacker can predict the session ID used during a transaction to perform spoofing and session hijacking.

Abstraction

Detailed

Typical severity

High

Likelihood of attack

High

Understand the attack

What is this attack pattern?

This attack targets predictable session ID in order to gain privileges. The attacker can predict the session ID used during a transaction to perform spoofing and session hijacking.

Execution flow

How does the attack proceed, step by step?

1

Explore

Find Session IDs

The attacker interacts with the target host and finds that session IDs are used to authenticate users.

Techniques used

  • An attacker makes many anonymous connections and records the session IDs assigned.
  • An attacker makes authorized connections and records the session tokens or credentials issued.

Characterize IDs

The attacker studies the characteristics of the session ID (size, format, etc.). As a results the attacker finds that legitimate session IDs are predictable.

Techniques used

  • Cryptanalysis. The attacker uses cryptanalysis to determine if the session IDs contain any cryptographic protections.
  • Pattern tests. The attacker looks for patterns (odd/even, repetition, multiples, or other arithmetic relationships) between IDs
  • Comparison against time. The attacker plots or compares the issued IDs to the time they were issued to check for correlation.
2

Experiment

Match issued IDs

The attacker brute forces different values of session ID and manages to predict a valid session ID.

Techniques used

  • The attacker models the session ID algorithm enough to produce a compatible session IDs, or just one match.
3

Exploit

Use matched Session ID

The attacker uses the falsified session ID to access the target system.

Techniques used

  • The attacker loads the session ID into their web browser and browses to restricted data or functionality.
  • The attacker loads the session ID into their network communications and impersonates a legitimate user to gain access to data or functionality.

Requirements

What does the attack require?

Prerequisites

  • The target host uses session IDs to keep track of the users.
  • Session IDs are used to control access to resources.
  • The session IDs used by the target host are predictable. For example, the session IDs are generated using predictable information (e.g., time).

Skills required

  • Low: There are tools to brute force session ID. Those tools require a low level of knowledge.
  • Medium: Predicting Session ID may require more computation work which uses advanced analysis such as statistical analysis.

Resources required

Not stated in the MITRE record.

Impact

What does a successful attack lead to?

Gain Privileges

Affected scopes: Confidentiality, Access Control, Authorization

Defence

How is it prevented and mitigated?

1
Use a strong source of randomness to generate a session ID.
2
Use adequate length session IDs
3
Do not use information available to the user in order to generate session ID (e.g., time).
4
Ideas for creating random numbers are offered by Eastlake [RFC1750]
5
Encrypt the session ID if you expose it to the user. For instance session ID can be stored in a cookie in encrypted format.

Real world

MITRE example instances

Example instance 1Detail
Jetty before 4.2.27, 5.1 before 5.1.12, 6.0 before 6.0.2, and 6.1 before 6.1.0pre3 generates predictable session identifiers using java.util.random, which makes it easier for remote attackers to guess a session identifier through brute force attacks, bypass authentication requirements, and possibly conduct cross-site request forgery attacks. See also: CVE-2006-6969
Example instance 2Detail
mod_usertrack in Apache 1.3.11 through 1.3.20 generates session ID's using predictable information including host IP address, system time and server process ID, which allows local users to obtain session ID's and bypass authentication when these session ID's are used for authentication. See also: CVE-2001-1534