CVE-2020-14318 Overview
A flaw was found in the way Samba handled file and directory permissions. An authenticated user could use this flaw to gain access to certain file and directory information which otherwise would be unavailable to the attacker. This improper privilege management vulnerability allows authenticated users to enumerate and access metadata about files and directories that should be restricted based on configured access controls.
Critical Impact
Authenticated attackers can bypass intended permission restrictions to access sensitive file and directory information, potentially exposing confidential data structures and enabling further reconnaissance for targeted attacks.
Affected Products
- Samba Samba (multiple versions)
- Red Hat Storage 3.0
- Red Hat Enterprise Linux 7.0 and 8.0
Discovery Timeline
- 2020-12-03 - CVE-2020-14318 published to NVD
- 2024-11-21 - Last updated in NVD database
Technical Details for CVE-2020-14318
Vulnerability Analysis
This vulnerability stems from improper privilege management (CWE-266) and incorrect privilege assignment for critical resources (CWE-269) within Samba's file and directory permission handling mechanisms. The flaw exists in how Samba validates and enforces access permissions when authenticated users request information about files and directories.
When an authenticated user interacts with Samba file shares, the server should properly validate that the requesting user has appropriate permissions before disclosing any file or directory metadata. However, due to this vulnerability, the permission checking logic fails to adequately restrict access, allowing authenticated users to obtain information about files and directories they should not be able to see.
The attack requires network access and valid authentication credentials, but does not require elevated privileges. An attacker with basic user access to a Samba share could leverage this flaw to enumerate directory structures, identify sensitive files, and gather information useful for planning further attacks against the system.
Root Cause
The root cause of this vulnerability lies in improper privilege management within Samba's access control implementation. The permission validation logic does not properly enforce all access restrictions, creating a gap between the configured permissions and the actual enforcement. This allows authenticated users to request and receive file and directory information that should be protected based on the access control lists (ACLs) configured on those resources.
Attack Vector
The attack vector for CVE-2020-14318 is network-based, requiring the attacker to have authenticated access to a Samba server. The attack flow involves:
- An attacker authenticates to a Samba server with valid but low-privileged credentials
- The attacker sends requests for file and directory information through normal SMB/CIFS protocol operations
- Due to the permission handling flaw, Samba returns information about files and directories that should be restricted
- The attacker can use this information disclosure to map sensitive directory structures and identify potentially valuable targets
The vulnerability requires no user interaction and can be exploited with low complexity once authentication is established. The impact is limited to confidentiality of information - the attacker cannot modify or delete files through this vulnerability alone.
Detection Methods for CVE-2020-14318
Indicators of Compromise
- Unusual file enumeration activity from authenticated users accessing directories outside their normal scope
- Increased SMB requests for file metadata from single user accounts
- Access attempts to restricted directories that return successful responses despite permission configurations
- Anomalous patterns of directory traversal requests from authenticated sessions
Detection Strategies
- Monitor Samba audit logs for permission check failures followed by successful information disclosures
- Implement file integrity monitoring to track access patterns to sensitive directories
- Deploy network traffic analysis to identify excessive SMB enumeration requests
- Configure Samba logging verbosity to capture detailed access control decisions
Monitoring Recommendations
- Enable detailed Samba logging with log level = 3 or higher for troubleshooting permission issues
- Review Samba access logs for patterns of information requests to restricted paths
- Implement SIEM rules to correlate authentication events with subsequent file enumeration activity
- Monitor for scanning behavior indicating reconnaissance against file shares
How to Mitigate CVE-2020-14318
Immediate Actions Required
- Update Samba to the latest patched version immediately
- Review and audit current file and directory permissions on all Samba shares
- Implement principle of least privilege for all authenticated users
- Consider temporarily restricting access to sensitive shares until patches are applied
Patch Information
Samba has released security patches to address this vulnerability. Organizations should apply updates from their distribution's package management system or directly from the Samba project. Detailed patch information is available from the Samba CVE-2020-14318 Advisory.
For Red Hat Enterprise Linux systems, patched packages are available through the standard update channels. Additional information can be found in the Red Hat Bug Report.
Distribution-specific advisories:
Workarounds
- Restrict network access to Samba servers to only trusted network segments
- Implement additional authentication requirements such as Kerberos with strict user validation
- Review and tighten ACLs on all shares to minimize exposure of sensitive directories
- Consider implementing host-based access controls in smb.conf using hosts allow and hosts deny directives
# Configuration example - Restrict host access in smb.conf
[global]
hosts allow = 192.168.1.0/24 127.0.0.1
hosts deny = ALL
[sensitive_share]
path = /srv/samba/sensitive
valid users = @trusted_group
read only = yes
browseable = no
Disclaimer: This content was generated using AI. While we strive for accuracy, please verify critical information with official sources.
