CVE-2021-28095 in OX Documents
Summary
by MITRE • 07/30/2021
OX Documents before 7.10.5-rev5 has Incorrect Access Control for documents that contain XML structures because hash collisions can occur, due to use of CRC32.
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Analysis
by VulDB Data Team • 08/06/2021
The vulnerability identified as CVE-2021-28095 affects OX Documents versions prior to 7.10.5-rev5 and represents a critical access control flaw that stems from improper handling of XML document structures. This vulnerability specifically targets the document processing engine where XML files are parsed and managed, creating a pathway for unauthorized access to sensitive content. The root cause lies in the implementation of hash functions used during document processing, where CRC32 algorithm is employed for generating hash values that are subsequently used to verify document integrity and control access permissions.
The technical flaw manifests through hash collision vulnerabilities that occur when multiple distinct XML documents produce identical CRC32 hash values. This collision exploitation allows malicious actors to craft specially designed XML documents that appear to have valid authentication signatures or access permissions, effectively bypassing the intended access control mechanisms. The vulnerability is particularly concerning because it operates at the core document processing layer where security decisions are made based on hash verification. When hash collisions occur, the system cannot distinguish between legitimate and malicious documents, leading to potential unauthorized access to restricted content. This flaw directly relates to CWE-327, which addresses broken or weak cryptographic algorithms, and specifically targets the use of CRC32 as a cryptographic hash function where its collision resistance properties are insufficient for security purposes.
The operational impact of this vulnerability extends beyond simple unauthorized access, creating potential data exfiltration risks and privilege escalation scenarios within environments using OX Documents. Attackers could exploit this weakness to gain access to confidential documents that should be restricted to specific users or groups, potentially compromising sensitive business information, intellectual property, or personal data. The vulnerability affects organizations that rely on OX Documents for collaborative document management, particularly in enterprise environments where document access control is critical. System administrators may not immediately detect such attacks since the malicious documents appear to be legitimate, making this vulnerability particularly dangerous for long-term persistence and stealthy data breaches.
Organizations should immediately implement the available patches and updates to OX Documents version 7.10.5-rev5 or later to remediate this vulnerability. The mitigation strategy should include comprehensive monitoring of document access logs to detect anomalous access patterns that might indicate exploitation attempts. Security teams should also consider implementing additional access controls and verification mechanisms beyond the default hash-based authentication. Organizations using older versions should conduct thorough vulnerability assessments of their document processing workflows and consider temporary workarounds such as restricting XML document uploads or implementing additional validation layers. The remediation process should include reviewing and updating security policies to address potential exploitation vectors and establishing incident response procedures specifically tailored to detect and respond to hash collision attacks in document processing systems. This vulnerability highlights the importance of avoiding weak cryptographic primitives in security-critical applications and aligns with ATT&CK technique T1078 for valid accounts and T1566 for credential harvesting through document-based attacks.