CVE-2023-41889 in Shirasagi
Summary
by MITRE • 09/16/2023
SHIRASAGI is a Content Management System. Prior to version 1.18.0, SHIRASAGI is vulnerable to a Post-Unicode normalization issue. This happens when a logical validation or a security check is performed before a Unicode normalization. The Unicode character equivalent of a character would resurface after the normalization. The fix is initially performing the Unicode normalization and then strip for all whitespaces and then checking for a blank string. This issue has been fixed in version 1.18.0.
If you want to get best quality of vulnerability data, you may have to visit VulDB.
Analysis
by VulDB Data Team • 09/16/2023
The SHIRASAGI content management system contains a post-unicode normalization vulnerability that affects versions prior to 1.18.0, representing a significant security flaw in the application's input validation and sanitization processes. This vulnerability stems from the improper order of operations during security checks, where logical validations and security assessments occur before Unicode normalization takes place. The flaw allows attackers to exploit character encoding inconsistencies that can bypass security measures designed to prevent malicious input. When the system processes input containing unicode characters, the normalization process occurs too late in the validation sequence, enabling certain character sequences to maintain their original form despite the normalization step. This creates a window where malicious inputs can slip through security checks that should have prevented them. The vulnerability specifically affects how the system handles whitespace characters and blank string validation, as the normalization process fails to properly account for unicode character equivalence after processing. According to CWE standards, this represents a weakness in input validation where the order of operations creates exploitable conditions. The issue falls under the broader category of unicode normalization problems that have been documented in various security contexts, where improper sequence of character processing can lead to bypasses of security controls.
The operational impact of this vulnerability extends beyond simple input validation failures, potentially allowing attackers to craft inputs that appear benign but contain hidden malicious payloads. When security checks are performed before normalization, attackers can leverage unicode character variations to evade detection mechanisms that rely on exact string matching or specific character sequences. The vulnerability becomes particularly concerning in contexts where the application performs access control checks or validates user input against security policies, as it could enable privilege escalation or unauthorized access to restricted resources. The fix implemented in version 1.18.0 addresses this by establishing a proper processing order that normalizes unicode characters first, then strips whitespace, and finally validates for blank strings. This approach ensures that all character variations are resolved to their canonical forms before any security decisions are made, preventing the bypass scenarios that occurred previously. The solution aligns with established security practices that emphasize the importance of proper input sanitization order, where normalization occurs before validation to prevent character-based attacks.
Security professionals should recognize this vulnerability as part of the broader category of character encoding attacks that have been documented in the ATT&CK framework under techniques related to input validation and evasion. The vulnerability demonstrates how seemingly minor implementation details in security controls can create significant weaknesses, particularly when dealing with complex character sets and internationalization features. Organizations using SHIRASAGI should prioritize upgrading to version 1.18.0 or later to address this vulnerability, as the fix represents a fundamental improvement in the application's security posture. The remediation approach taken by the developers follows industry best practices for handling unicode normalization in security contexts, emphasizing the importance of proper sequence in input processing. This vulnerability also highlights the need for comprehensive testing of internationalization features in security-critical applications, as unicode-related issues can often be overlooked during initial security assessments. The fix ensures that subsequent security checks operate on normalized character data, eliminating the possibility of bypassing validation through unicode character variations. This type of vulnerability is particularly relevant in web applications where user input is processed through multiple validation layers, as it demonstrates how the timing and ordering of security operations can determine the effectiveness of the overall protection scheme.