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CWE

Improper Output Neutralization for Logs

ID: 117		Date: (C)2012-05-14 (M)2022-10-10
Type: weakness		Status: DRAFT
Abstraction Type: Base

Description

The software does not neutralize or incorrectly neutralizes output that is written to logs.

Extended Description

This can allow an attacker to forge log entries or inject malicious content into logs.

Log forging vulnerabilities occur when:

Data enters an application from an untrusted source.

The data is written to an application or system log file.

Likelihood of Exploit: Medium

Applicable Platforms
Language Class: All

Time Of Introduction

Implementation

Related Attack Patterns

Common Consequences

Scope	Technical Impact	Notes
Integrity Confidentiality Availability Non-Repudiation	Modify application data Hide activities Execute unauthorized code or commands	Interpretation of the log files may be hindered or misdirected if an attacker can supply data to the application that is subsequently logged verbatim. In the most benign case, an attacker may be able to insert false entries into the log file by providing the application with input that includes appropriate characters. Forged or otherwise corrupted log files can be used to cover an attacker's tracks, possibly by skewing statistics, or even to implicate another party in the commission of a malicious act. If the log file is processed automatically, the attacker can render the file unusable by corrupting the format of the file or injecting unexpected characters. An attacker may inject code or other commands into the log file and take advantage of a vulnerability in the log processing utility.

Detection Methods
None

Potential Mitigations

Phase	Strategy	Description
Implementation	Input Validation	Assume all input is malicious. Use an "accept known good" input validation strategy, i.e., use a whitelist of acceptable inputs that strictly conform to specifications. Reject any input that does not strictly conform to specifications, or transform it into something that does. When performing input validation, consider all potentially relevant properties, including length, type of input, the full range of acceptable values, missing or extra inputs, syntax, consistency across related fields, and conformance to business rules. As an example of business rule logic, "boat" may be syntactically valid because it only contains alphanumeric characters, but it is not valid if the input is only expected to contain colors such as "red" or "blue." Do not rely exclusively on looking for malicious or malformed inputs (i.e., do not rely on a blacklist). A blacklist is likely to miss at least one undesirable input, especially if the code's environment changes. This can give attackers enough room to bypass the intended validation. However, blacklists can be useful for detecting potential attacks or determining which inputs are so malformed that they should be rejected outright.
Implementation	Output Encoding	Use and specify an output encoding that can be handled by the downstream component that is reading the output. Common encodings include ISO-8859-1, UTF-7, and UTF-8. When an encoding is not specified, a downstream component may choose a different encoding, either by assuming a default encoding or automatically inferring which encoding is being used, which can be erroneous. When the encodings are inconsistent, the downstream component might treat some character or byte sequences as special, even if they are not special in the original encoding. Attackers might then be able to exploit this discrepancy and conduct injection attacks; they even might be able to bypass protection mechanisms that assume the original encoding is also being used by the downstream component.
Implementation	Input Validation	Inputs should be decoded and canonicalized to the application's current internal representation before being validated (CWE-180). Make sure that the application does not decode the same input twice (CWE-174). Such errors could be used to bypass whitelist validation schemes by introducing dangerous inputs after they have been checked.

Relationships

Related CWE	Type	View	Chain
CWE-117 ChildOf CWE-895	Category	CWE-888

Demonstrative Examples (Details)

The following web application code attempts to read an integer value from a request object. If the parseInt call fails, then the input is logged with an error message indicating what happened.

Observed Examples

CVE-2006-4624 : Chain: inject fake log entries with fake timestamps using CRLF injection

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
7 Pernicious Kingdoms		Log Forging

References:

G. Hoglund G. McGraw .Exploiting Software: How to Break Code. Addison-Wesley. Published on February 2004.
A. Muffet .The night the log was forged.
OWASP .OWASP TOP 10.


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