CVE-2005-4881 in Linux
Summary
by MITRE
The netlink subsystem in the Linux kernel 2.4.x before 2.4.37.6 and 2.6.x before 2.6.13-rc1 does not initialize certain padding fields in structures, which might allow local users to obtain sensitive information from kernel memory via unspecified vectors, related to the (1) tc_fill_qdisc, (2) tcf_fill_node, (3) neightbl_fill_info, (4) neightbl_fill_param_info, (5) neigh_fill_info, (6) rtnetlink_fill_ifinfo, (7) rtnetlink_fill_iwinfo, (8) vif_delete, (9) ipmr_destroy_unres, (10) ipmr_cache_alloc_unres, (11) ipmr_cache_resolve, (12) inet6_fill_ifinfo, (13) tca_get_fill, (14) tca_action_flush, (15) tcf_add_notify, (16) tc_dump_action, (17) cbq_dump_police, (18) __nlmsg_put, (19) __rta_fill, (20) __rta_reserve, (21) inet6_fill_prefix, (22) rsvp_dump, and (23) cbq_dump_ovl functions.
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Analysis
by VulDB Data Team • 08/24/2021
The vulnerability described in CVE-2005-4881 represents a critical information disclosure issue within the Linux kernel's netlink subsystem affecting versions prior to 2.4.37.6 and 2.6.13-rc1. This flaw stems from improper initialization of padding fields in kernel data structures, creating potential pathways for local attackers to access sensitive kernel memory contents through unspecified vectors. The vulnerability specifically impacts multiple functions within the netlink subsystem, each handling different aspects of network configuration and monitoring operations. The root cause aligns with CWE-1283, which addresses improper initialization of padding bytes in data structures, making it a classic case of information exposure through uninitialized memory. Attackers can exploit this weakness by leveraging the affected netlink functions to read kernel memory, potentially extracting confidential information such as cryptographic keys, passwords, or other sensitive data stored in memory regions.
The technical implementation of this vulnerability occurs at the kernel level where the netlink subsystem handles communication between user-space applications and kernel-space network components. When these specific functions process network information requests, they fail to properly initialize padding fields in their data structures before populating them with kernel data. This incomplete initialization leaves remnants of previous kernel operations in memory, creating a window for information leakage. The affected functions span across various network management operations including traffic control, neighbor discovery, routing information, and interface configuration. Each of these functions serves different network monitoring and management purposes, making the vulnerability particularly dangerous as it can be exploited through multiple attack vectors. The vulnerability operates under the ATT&CK framework category of T1005 - Data from Local System, where adversaries can extract sensitive information from kernel memory through legitimate system interfaces.
The operational impact of this vulnerability extends beyond simple information disclosure, as it can enable more sophisticated attacks when combined with other exploitation techniques. Local users with minimal privileges can potentially access kernel memory contents that might contain sensitive information about network configurations, cryptographic materials, or system internals. The exploitation requires local access to the system but does not need elevated privileges, making it particularly concerning for multi-tenant environments or systems where untrusted users have access to local accounts. The vulnerability affects critical network management functions that are frequently accessed during normal system operation, increasing the likelihood of successful exploitation. System administrators may not immediately detect this information leakage as it occurs through legitimate kernel interfaces, making the attack stealthy and difficult to trace. The impact is significant for systems handling sensitive network information or operating in environments where kernel memory contents could reveal system vulnerabilities or confidential data.
Mitigation strategies for CVE-2005-4881 primarily involve upgrading to patched kernel versions where the padding fields in affected structures are properly initialized. System administrators should prioritize applying the security patches released by kernel maintainers for versions 2.4.37.6 and 2.6.13-rc1 or later. The vulnerability can also be addressed through network segmentation and access control measures that limit local user privileges, reducing the attack surface for local exploitation attempts. Additional defensive measures include monitoring for unusual netlink traffic patterns that might indicate exploitation attempts, implementing kernel memory protection mechanisms, and conducting regular security audits of kernel modules. The fix implemented in patched versions typically involves ensuring proper initialization of padding fields in all affected kernel data structures, preventing the leakage of uninitialized memory contents. Organizations should also consider implementing kernel hardening techniques such as stack canaries, address space layout randomization, and other memory protection mechanisms to further reduce the impact of similar vulnerabilities. Regular kernel updates and security monitoring are essential to maintain protection against this and related information disclosure vulnerabilities.