CVE-2011-1758 in SSSD
Summary
by MITRE
The krb5_save_ccname_done function in providers/krb5/krb5_auth.c in System Security Services Daemon (SSSD) 1.5.x before 1.5.7, when automatic ticket renewal and offline authentication are configured, uses a pathname string as a password, which allows local users to bypass Kerberos authentication by listing the /tmp directory to obtain the pathname.
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Analysis
by VulDB Data Team • 11/07/2021
The vulnerability identified as CVE-2011-1758 affects the System Security Services Daemon (SSSD) version 1.5.x prior to 1.5.7, specifically within the krb5_save_ccname_done function located in providers/krb5/krb5_auth.c. This flaw represents a critical security weakness that undermines the integrity of Kerberos authentication mechanisms when certain configuration parameters are enabled. The vulnerability arises from the improper handling of authentication credentials during the ticket renewal process, creating a scenario where local attackers can exploit system behavior to bypass authentication controls.
The technical implementation of this vulnerability stems from how SSSD manages Kerberos credential caches when automatic ticket renewal and offline authentication features are active. The krb5_save_ccname_done function inadvertently treats a pathname string as if it were a password value, creating an insecure credential handling pattern that violates fundamental security principles. This misimplementation occurs because the system stores sensitive credential information in a location where it becomes accessible through directory listing operations, specifically within the /tmp directory where temporary files are typically stored.
The operational impact of this vulnerability is significant as it allows local users to bypass Kerberos authentication entirely by simply listing the contents of the /tmp directory. This attack vector demonstrates a clear violation of the principle of least privilege and represents a privilege escalation vulnerability that can be exploited by any local user with basic file system access. The attack requires minimal technical expertise and can be executed through standard directory listing commands, making it particularly dangerous in multi-user environments where local access is common. This vulnerability essentially undermines the entire Kerberos authentication framework by exposing credential information that should remain protected.
The security implications extend beyond simple credential exposure, as this vulnerability can be leveraged to gain unauthorized access to systems and services that rely on SSSD for authentication. From an ATT&CK framework perspective, this vulnerability maps to privilege escalation techniques and credential access methods, specifically leveraging the T1003.001 sub-technique for credential dumping. The vulnerability also aligns with CWE-255, which addresses credentials management flaws, and CWE-310, which covers cryptographic issues related to improper handling of sensitive data. Organizations using SSSD with automatic ticket renewal and offline authentication capabilities are particularly at risk, as the vulnerability can be exploited to impersonate legitimate users and access protected resources.
Mitigation strategies for CVE-2011-1758 require immediate patching of affected SSSD versions to 1.5.7 or later, which contains the necessary fixes for the credential handling issue. Additionally, system administrators should review and tighten permissions on temporary directories, particularly /tmp, to prevent unauthorized listing of sensitive files. The recommended configuration approach involves disabling automatic ticket renewal and offline authentication features when they are not strictly required, or ensuring that proper file system permissions are enforced to prevent local users from accessing temporary credential files. Organizations should also implement monitoring solutions to detect unauthorized access attempts to temporary directories and credential cache files, as well as conduct regular security audits to identify potential exposure to similar credential handling vulnerabilities.