Overflow Variables and Tags
Attack Pattern ID: 46 (Detailed Attack Pattern Completeness: Complete)Typical Severity: HighStatus: Draft
+ Description


This type of attack leverages the use of tags or variables from a formatted configuration data to cause buffer overflow. The attacker crafts a malicious HTML page or configuration file that includes oversized strings, thus causing an overflow.

Attack Execution Flow

  1. The attacker modifies a tag or variable from a formatted configuration data. For instance she changes it to an oversized string.

  2. The target program consumes the data modified by the attacker without prior boundary checking. As a consequence, a buffer overflow occurs and at worst remote code execution may follow.

+ Attack Prerequisites

The target program consumes user-controllable data in the form of tags or variables.

The target program does not perform sufficient boundary checking.

+ Typical Likelihood of Exploit

Likelihood: High

+ Methods of Attack
  • Injection
+ Examples-Instances


A buffer overflow vulnerability exists in the Yamaha MidiPlug that can be accessed via a Text variable found in an EMBED tag.

Related Vulnerabilities



A buffer overflow in Exim allows local users to gain root privileges by providing a long :include: option in a .forward file.

Related Vulnerabilities


+ Attacker Skills or Knowledge Required

Skill or Knowledge Level: Low

An attacker can simply overflow a buffer by inserting a long string into an attacker-modifiable injection vector. The result can be a DoS.

Skill or Knowledge Level: High

Exploiting a buffer overflow to inject malicious code into the stack of a software system or even the heap can require a higher skill level.

+ Probing Techniques

An attacker can modify the variables and tag exposed by the target program.

An attacker can automate the probing by input injection with script or automated tools.

+ Solutions and Mitigations

Use a language or compiler that performs automatic bounds checking.

Use an abstraction library to abstract away risky APIs. Not a complete solution.

Compiler-based canary mechanisms such as StackGuard, ProPolice and the Microsoft Visual Studio /GS flag. Unless this provides automatic bounds checking, it is not a complete solution.

Use OS-level preventative functionality. Not a complete solution.

Do not trust input data from user. Validate all user input.

+ Attack Motivation-Consequences
  • Denial of Service
  • Run Arbitrary Code
  • Information Leakage
  • Data Modification
+ Injection Vector

The variable or tag exposed to the user.

+ Payload

The new value of the variable or tag (could be an oversized string).

+ Activation Zone

When the function returns control to the main program, it jumps to the return address portion of the stack frame. Unfortunately that return address may have been overwritten by the overflowed buffer and the address may contain a call to a privileged command or to a malicious code.

+ Payload Activation Impact

The most common is remote code execution.

+ Related Weaknesses
CWE-IDWeakness NameWeakness Relationship Type
120Buffer Copy without Checking Size of Input ('Classic Buffer Overflow')Targeted
118Improper Access of Indexable Resource ('Range Error')Targeted
119Failure to Constrain Operations within the Bounds of a Memory BufferTargeted
74Failure to Sanitize Data into a Different Plane ('Injection')Targeted
20Improper Input ValidationTargeted
680Integer Overflow to Buffer OverflowTargeted
733Compiler Optimization Removal or Modification of Security-critical CodeSecondary
697Insufficient ComparisonTargeted
+ Related Attack Patterns
NatureTypeIDNameDescriptionView(s) this relationship pertains toView\(s\)
PeerOfAttack PatternAttack Pattern8Buffer Overflow in an API Call 
Mechanism of Attack1000
PeerOfAttack PatternAttack Pattern10Buffer Overflow via Environment Variables 
Mechanism of Attack1000
ChildOfAttack PatternAttack Pattern100Overflow Buffers 
Mechanism of Attack (primary)1000
+ Related Security Principles
  • Reluctance to trust

+ Purposes
  • Penetration
  • Exploitation
+ CIA Impact
Confidentiality Impact: HighIntegrity Impact: HighAvailability Impact: High
+ Technical Context
Architectural Paradigms
+ References
G. Hoglund and G. McGraw. "Exploiting Software: How to Break Code". Addison-Wesley. February 2004.

CWE - Buffer Errors

+ Content History
G. Hoglund and G. McGraw. Exploiting Software: How to Break Code. Addison-Wesley, February 2004.Cigital, Inc2007-03-01
Eric DalciCigital, Inc2007-02-13Fleshed out content to CAPEC schema from the original descriptions in "Exploiting Software"
Sean BarnumCigital, Inc2007-03-05Review and revise
Richard StruseVOXEM, Inc2007-03-26Review and feedback leading to changes in Related Attack Patterns
Sean BarnumCigital, Inc2007-04-13Modified pattern content according to review and feedback