CVE-2003-0689 in C Library
Summary
by MITRE
The getgrouplist function in GNU libc (glibc) 2.2.4 and earlier allows attackers to cause a denial of service (segmentation fault) and execute arbitrary code when a user is a member of a large number of groups, which can cause a buffer overflow.
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Analysis
by VulDB Data Team • 06/29/2021
The vulnerability identified as CVE-2003-0689 represents a critical buffer overflow flaw within the GNU C Library implementation that affects systems running glibc versions 2.2.4 and earlier. This vulnerability specifically targets the getgrouplist function which is responsible for retrieving group membership information for a given user account. When a user account belongs to an excessive number of groups, the function fails to properly validate buffer boundaries during the group list construction process, creating a condition where memory corruption can occur. The flaw stems from insufficient input validation and inadequate buffer size management within the library's group membership handling code.
The technical exploitation of this vulnerability occurs when the getgrouplist function attempts to store group identifiers in a buffer that is not sufficiently sized to accommodate the complete group membership list. As the number of groups increases beyond the allocated buffer space, memory overwrite conditions arise that can result in segmentation faults or more critically, arbitrary code execution. This buffer overflow vulnerability is classified as a classic stack-based buffer overflow when the function processes group membership data, potentially allowing attackers to manipulate program execution flow through carefully crafted group membership structures. The vulnerability directly maps to CWE-121, which describes stack-based buffer overflow conditions, and CWE-122, which covers heap-based buffer overflow scenarios that can occur during dynamic memory allocation.
The operational impact of CVE-2003-0689 extends beyond simple denial of service conditions to encompass full system compromise when exploited properly. Systems affected by this vulnerability become susceptible to privilege escalation attacks, where malicious users can leverage the buffer overflow to execute arbitrary code with the privileges of the targeted user account. The vulnerability is particularly dangerous in multi-user environments where users may belong to numerous groups through various membership mechanisms such as LDAP integration, Active Directory synchronization, or complex group hierarchy structures. Network services running under user contexts that invoke getgrouplist for authentication or authorization purposes become prime targets for exploitation, potentially allowing attackers to gain unauthorized access to sensitive system resources. This vulnerability aligns with ATT&CK technique T1068 which describes the exploitation of legitimate credentials and system privileges to execute malicious code.
Mitigation strategies for CVE-2003-0689 require immediate system updates to glibc versions 2.3.0 or later where the buffer overflow has been corrected through improved input validation and proper buffer size calculations. Organizations should implement group membership audits to identify accounts with unusually high group counts and reduce membership to reasonable levels. System administrators should also consider implementing access controls that limit the number of groups a user can belong to, particularly in environments where LDAP or other centralized authentication systems are used. The vulnerability demonstrates the importance of proper software patch management and continuous security monitoring, as it represents a fundamental flaw in a core system library that affects the entire operating system stack. Additionally, implementing runtime protections such as stack canaries and address space layout randomization can provide additional defense-in-depth measures against exploitation attempts.