CVE-2017-8449 in X-Pack Security
Summary
by MITRE
X-Pack Security 5.2.x would allow access to more fields than the user should have seen if the field level security rules used a mix of grant and exclude rules when merging multiple rules with field level security rules for the same index.
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Analysis
by VulDB Data Team • 10/18/2019
The vulnerability identified as CVE-2017-8449 resides within the X-Pack Security component of Elasticsearch versions 5.2.x, specifically affecting field level security implementations. This issue represents a privilege escalation weakness that undermines the core security principle of least privilege by allowing unauthorized data access. The flaw manifests when field level security rules are configured with a combination of grant and exclude directives, creating an unexpected behavior in the rule merging process that results in over-permissive access controls.
The technical root cause of this vulnerability stems from how Elasticsearch processes field level security rules when multiple rule sets are applied to the same index. When administrators define access policies using both explicit grant permissions and exclude restrictions, the system fails to properly merge these conflicting directives. This improper merging mechanism allows fields that should be excluded based on security rules to remain accessible to users, effectively bypassing the intended access controls. The vulnerability specifically affects the field level security feature within X-Pack Security, which is designed to restrict user access to specific fields within documents stored in Elasticsearch indices.
The operational impact of CVE-2017-8449 is significant as it creates a backdoor for unauthorized data access that could expose sensitive information to users who should not have visibility into certain fields. This weakness particularly affects organizations that rely on field level security to protect confidential data such as personally identifiable information, financial records, or proprietary business data. Attackers could exploit this vulnerability by crafting access requests that leverage the flawed rule merging process to gain access to restricted fields, potentially leading to data breaches, compliance violations, and regulatory penalties. The vulnerability is particularly dangerous because it operates silently without generating obvious audit trail indicators, making detection challenging.
Organizations affected by this vulnerability should immediately implement mitigations including updating to Elasticsearch versions that have addressed this issue, reviewing and restructuring existing field level security rules to avoid mixing grant and exclude directives for the same indices, and implementing additional monitoring controls to detect unauthorized access patterns. Security teams should also conduct comprehensive audits of field level security configurations to identify and correct any rule combinations that could trigger this behavior. From a compliance perspective, this vulnerability directly impacts requirements under standards such as iso 27001, pci dss, and gdpr, as it creates potential data exposure scenarios that violate data protection principles. The vulnerability aligns with CWE-284 which addresses improper access control, and represents a specific implementation weakness in the access control mechanism that could be categorized under ATT&CK technique T1078 for valid accounts and T1566 for social engineering. Organizations should consider implementing additional security controls such as data loss prevention measures and enhanced logging to compensate for the weakened access control enforcement until the underlying vulnerability is fully resolved through official patches and updates.