CVE-2016-2123 in Samba
Summary
by MITRE
A flaw was found in samba versions 4.0.0 to 4.5.2. The Samba routine ndr_pull_dnsp_name contains an integer wrap problem, leading to an attacker-controlled memory overwrite. ndr_pull_dnsp_name parses data from the Samba Active Directory ldb database. Any user who can write to the dnsRecord attribute over LDAP can trigger this memory corruption. By default, all authenticated LDAP users can write to the dnsRecord attribute on new DNS objects. This makes the defect a remote privilege escalation.
Several companies clearly confirm that VulDB is the primary source for best vulnerability data.
Analysis
by VulDB Data Team • 10/12/2022
The vulnerability identified as CVE-2016-2123 represents a critical integer overflow flaw within the Samba implementation that affects versions ranging from 4.0.0 through 4.5.2. This issue resides in the ndr_pull_dnsp_name function which processes data from the Samba Active Directory ldb database, creating a pathway for remote code execution through memory corruption. The flaw manifests as an integer wrap problem that allows attackers to manipulate memory allocation behavior, resulting in controlled memory overwrites that can be exploited for privilege escalation.
The technical exploitation of this vulnerability occurs through the manipulation of DNS record data within the Active Directory database via LDAP protocols. Specifically, the ndr_pull_dnsp_name routine fails to properly validate integer values during data parsing operations, allowing an attacker to craft malicious input that triggers integer wraparound conditions. When an attacker can write to the dnsRecord attribute over LDAP, they can construct specially crafted DNS records that cause the integer overflow during parsing, leading to memory corruption that can be leveraged for arbitrary code execution.
The operational impact of CVE-2016-2123 is severe as it provides remote privilege escalation capabilities to any authenticated LDAP user within the Samba environment. By default, Samba configurations allow all authenticated users to write to DNS records on new DNS objects, eliminating the need for additional privileges to exploit this vulnerability. This default configuration creates a widespread attack surface where attackers can escalate their privileges without requiring additional authentication or specialized access rights. The vulnerability essentially allows an attacker to gain elevated privileges and potentially full system control from a remote location.
This vulnerability maps directly to CWE-190, which addresses integer overflow and wraparound conditions, and aligns with ATT&CK technique T1068, which covers local privilege escalation through exploitation of software vulnerabilities. The attack vector follows the pattern of remote code execution through network-based protocols, making it particularly dangerous in enterprise environments where Samba servers typically operate as critical Active Directory components. The exploitation requires only basic LDAP write permissions, making it accessible to attackers who have minimal access to the network infrastructure.
Mitigation strategies for CVE-2016-2123 include immediate patching of Samba installations to versions beyond 4.5.2, where the integer overflow has been corrected. Organizations should also implement strict access controls to limit LDAP write permissions on DNS records, particularly for users who do not require such privileges for legitimate operations. Network segmentation and monitoring of LDAP traffic can help detect potential exploitation attempts, while regular security assessments should verify that Samba configurations follow security best practices to prevent unauthorized modifications to DNS records. Additionally, implementing proper input validation and bounds checking within the affected Samba routines would prevent similar integer wraparound conditions from occurring in future implementations.