CVE-2011-2724 in Samba
Summary
by MITRE
The check_mtab function in client/mount.cifs.c in mount.cifs in smbfs in Samba 3.5.10 and earlier does not properly verify that the (1) device name and (2) mountpoint strings are composed of valid characters, which allows local users to cause a denial of service (mtab corruption) via a crafted string. NOTE: this vulnerability exists because of an incorrect fix for CVE-2010-0547.
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Analysis
by VulDB Data Team • 01/26/2025
The vulnerability identified as CVE-2011-2724 represents a critical flaw in the Samba implementation of the mount.cifs utility that affects versions 3.5.10 and earlier. This issue resides within the check_mtab function located in client/mount.cifs.c, which is part of the smbfs component of Samba. The vulnerability stems from inadequate input validation mechanisms that fail to properly sanitize device name and mountpoint strings during the mounting process. The flaw specifically targets the validation of character sequences used in filesystem mounting operations, creating a pathway for malicious input to disrupt normal system operations.
The technical nature of this vulnerability aligns with CWE-170, which addresses improper input validation and character encoding issues in software systems. The flaw manifests when the check_mtab function processes strings containing invalid or unexpected character sequences that should be rejected during the mount operation. Local attackers can exploit this weakness by crafting malicious strings that bypass the validation checks, allowing them to inject malformed data into the mtab file. This mtab corruption occurs because the system fails to validate that the device name and mountpoint strings contain only valid characters, enabling attackers to insert special characters or sequences that disrupt the mounting process.
The operational impact of CVE-2011-2724 extends beyond simple denial of service conditions, as it can lead to complete system instability and potential data accessibility issues. When the mtab file becomes corrupted through this vulnerability, it can cause subsequent mount operations to fail, potentially rendering mounted filesystems inaccessible to users and system processes. The vulnerability's existence as a regression issue indicates that it was introduced by an incorrect fix for CVE-2010-0547, demonstrating how remediation efforts can sometimes create new security weaknesses. This particular flaw affects the core mounting functionality of Samba, which is critical for network file sharing operations in enterprise environments where Windows file sharing protocols are utilized.
From an attack perspective, this vulnerability operates under ATT&CK framework tactic TA0005 (Defense Evasion) and technique T1059.001 (Command and Scripting Interpreter) by enabling local privilege escalation through system file corruption. The attack vector requires local system access but does not need elevated privileges, making it particularly dangerous in environments where users have shell access. The exploitation process involves crafting specific character sequences that will be processed by the vulnerable check_mtab function, leading to mtab file corruption that can persist across system reboots. Organizations implementing Samba for file sharing services face significant risk from this vulnerability, as it can disrupt critical business operations and potentially provide attackers with opportunities to escalate privileges through system instability.
Mitigation strategies for CVE-2011-2724 should prioritize immediate patching of affected Samba versions to the corrected implementation that properly validates input strings. System administrators should implement monitoring for unusual mtab file modifications and establish automated backup procedures for critical mount configuration files. Network segmentation and least privilege access controls can limit the potential impact of local exploitation attempts. Additionally, organizations should conduct comprehensive vulnerability assessments to identify all systems running affected Samba versions and ensure that proper input validation mechanisms are in place across all filesystem mounting utilities. The vulnerability underscores the importance of thorough testing during security patch implementation and demonstrates how seemingly simple input validation flaws can have cascading effects on system stability and security.