CVE-2018-5773 : Security Advisory and Response

A problem has been identified in markdown2 (also known as python-markdown2) up to version 2.3.5. The safe_mode functionality, designed to protect against XSS attacks by sanitizing user input, is defective and fails to correctly escape the input. This flaw allows an attacker to execute XSS attacks using a carefully constructed payload. An example of this vulnerability is when the ending '>' character is deliberately omitted from an IMG tag.

Understanding CVE-2018-5773

An issue was discovered in markdown2 (aka python-markdown2) through 2.3.5. The safe_mode feature, which is supposed to sanitize user input against XSS, is flawed and does not escape the input properly. With a crafted payload, XSS can be triggered, as demonstrated by omitting the final '>' character from an IMG tag.

What is CVE-2018-5773?

Vulnerability in markdown2 (python-markdown2) up to version 2.3.5
Safe_mode feature designed to protect against XSS attacks is defective
Allows attackers to execute XSS attacks using a carefully crafted payload

The Impact of CVE-2018-5773

Potential for attackers to execute XSS attacks
Risk of unauthorized code execution through manipulated input

Technical Details of CVE-2018-5773

The technical details of the CVE-2018-5773 vulnerability are as follows:

Vulnerability Description

Safe_mode functionality in markdown2 up to version 2.3.5 is flawed
Fails to properly escape user input, enabling XSS attacks

Affected Systems and Versions

Systems using markdown2 (python-markdown2) up to version 2.3.5

Exploitation Mechanism

Attackers can exploit the vulnerability by crafting payloads that omit the '>' character from certain tags

Mitigation and Prevention

To mitigate the risks associated with CVE-2018-5773, consider the following steps:

Immediate Steps to Take

Upgrade markdown2 to a patched version that addresses the vulnerability
Implement input validation to prevent malicious payloads

Long-Term Security Practices

Regularly update software and libraries to the latest secure versions
Conduct security audits to identify and address vulnerabilities proactively

Patching and Updates

Stay informed about security advisories and patches released by the software vendor
Apply patches promptly to ensure protection against known vulnerabilities