CVE-2019-20868 in Mattermost Server
Summary
by MITRE
An issue was discovered in Mattermost Server before 5.11.0. Invite IDs were improperly generated.
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Analysis
by VulDB Data Team • 10/25/2020
The vulnerability identified as CVE-2019-20868 represents a critical weakness in the Mattermost server authentication and access control mechanisms. This issue affects versions prior to 5.11.0 and specifically targets the generation of invite identifiers used within the platform's invitation system. The improper generation of these identifiers creates a significant security risk that can be exploited by malicious actors to gain unauthorized access to private channels and restricted areas of the Mattermost environment. The vulnerability lies in the insufficient randomness and predictability of the invite ID generation algorithm, which violates fundamental security principles for cryptographic token creation.
The technical flaw manifests in the cryptographic weakness of the invite ID generation process, where the system fails to implement proper entropy sources and random number generation techniques. This weakness can be categorized under CWE-330 Use of Insufficiently Random Values, which specifically addresses the use of predictable or insufficiently random data in security-critical contexts. The vulnerability allows attackers to potentially guess or brute-force invite IDs, thereby bypassing the intended access controls that should protect private channels and user communications. The predictability of these identifiers stems from inadequate seeding of random number generators and lack of proper cryptographic strength in the generation algorithm, making the system susceptible to automated exploitation attempts.
The operational impact of this vulnerability extends beyond simple unauthorized access to encompass broader security implications for organizations relying on Mattermost for secure communications. Attackers can exploit this weakness to gain access to private channels, view confidential messages, and potentially escalate privileges within the system. The vulnerability affects the integrity and confidentiality of communications, as it undermines the trust model that Mattermost relies upon for its collaborative platform. Organizations may experience data breaches, unauthorized information disclosure, and potential compliance violations when this vulnerability is exploited, particularly in regulated environments where secure communication channels are mandatory. The attack surface is particularly concerning given that Mattermost is widely used in enterprise environments where sensitive business communications and collaboration occur.
Mitigation strategies for CVE-2019-20868 require immediate implementation of the vendor-provided patch for Mattermost Server version 5.11.0 and subsequent releases, which address the cryptographic weaknesses in invite ID generation. Organizations should also conduct thorough assessments of their existing invite IDs to identify and invalidate any compromised identifiers that may have been generated before the patch was applied. Security teams should implement monitoring procedures to detect unusual access patterns or attempts to use invite IDs that may indicate exploitation attempts. The fix addresses the underlying cryptographic implementation by ensuring proper random number generation with sufficient entropy and by incorporating industry-standard cryptographic practices for token creation. Additionally, organizations should consider implementing additional access controls and monitoring mechanisms around invitation systems to detect and prevent unauthorized access attempts. This vulnerability demonstrates the critical importance of proper cryptographic implementation in security-critical components and aligns with ATT&CK technique T1078 Valid Accounts, as it enables adversaries to obtain valid access through predictable authentication mechanisms. The remediation process should include comprehensive testing to ensure that the patched version properly implements secure random number generation and that existing invitations are handled appropriately to prevent continued exposure.