CVE-2026-97476 in Linux
Summary
by MITRE • 09/24/2026
In the Linux kernel, the following vulnerability has been resolved:
rds: filter RDS_INFO_* getsockopt by caller's netns
The RDS_INFO_* family of getsockopt(2) options reads several file-scope global lists that are not per-netns:
rds_sock_info / rds6_sock_info, rds_sock_inc_info / rds6_sock_inc_info -> rds_sock_list rds_tcp_tc_info / rds6_tcp_tc_info -> rds_tcp_tc_list rds_conn_info / rds6_conn_info, rds_conn_message_info_cmn (for the *_SEND_MESSAGES and *_RETRANS_MESSAGES variants), rds_for_each_conn_info (for RDS_INFO_IB_CONNECTIONS) -> rds_conn_hash[]
The handlers do not filter by the caller's network namespace. rds_info_getsockopt() has no netns or capable() check, and rds_create() has no capable() check, so AF_RDS is reachable from an unprivileged user namespace. As a result, an unprivileged caller in a fresh user_ns plus netns can read the bound address and sock inode of every RDS socket on the host, the peer address of incoming messages on every RDS socket on the host, the peer address and TCP sequence numbers of every rds-tcp connection on the host, and the peer address and RDS sequence numbers of every RDS connection on the host.
The rds-tcp transport is reachable from a non-initial netns (see rds_set_transport()), so a one-shot init_net gate at rds_info_getsockopt() would deny legitimate per-netns visibility to rds-tcp callers. Instead, filter at each handler by comparing the netns of the caller's socket to the netns of the list entry, or to rds_conn_net(conn) for connection paths. Only copy entries whose netns matches the caller. Counters (RDS_INFO_COUNTERS) are aggregate statistics and remain global.
Reproducer (KASAN VM, rds and rds_tcp loaded): an AF_RDS socket binds 127.0.0.1:4242 in init_net as root. A child process enters a fresh user_ns plus netns and opens AF_RDS there, then calls getsockopt(SOL_RDS, RDS_INFO_SOCKETS). Before this change, the child sees the init_net socket. After this change, the child sees zero entries.
Drop the rds_sock_count, rds_tcp_tc_count, and rds6_tcp_tc_count globals. v2 used them for the size precheck and lens->nr; v3 replaced the precheck with a per-ns count from a first pass over the list, so the globals have no remaining readers. The matching increments and decrements in rds_create()/rds_destroy_sock() and rds_tcp_set_callbacks()/rds_tcp_restore_callbacks() go away with them. Reported by the kernel test robot under clang W=1.
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Analysis
by VulDB Data Team • 09/24/2026
The Linux Kernel Remote Direct Memory Access subsystem contains a critical information disclosure vulnerability stemming from improper network namespace isolation within its socket control interface. The RDS_INFO family of getsockopt options is designed to retrieve detailed state information about active connections, including bound addresses, peer endpoints, and sequence numbers. However, the underlying implementation fails to filter these queries based on the caller's network namespace context. Specifically, handlers such as rds_info_getsockopt access global data structures like rds_sock_list, rds_tcp_tc_list, and rds_conn_hash without verifying whether the requesting process resides in a different network namespace than the sockets being queried. This architectural oversight allows any user with access to AF_RDS socket operations to enumerate sensitive networking details belonging to other namespaces on the same host.
The severity of this flaw is amplified by the fact that creating an RDS socket does not require elevated privileges or specific capability checks in non-initial network namespaces. Consequently, an unprivileged attacker operating within a fresh user namespace and a distinct network namespace can exploit this lack of isolation. By invoking getsockopt with options such as RDS_INFO_SOCKETS, RDS_INFO_CONNECTIONS, or related variants for TCP and InfiniBand transports, the attacker can retrieve comprehensive data about all active RDS sockets on the system. This includes local bound addresses, remote peer addresses, TCP sequence numbers, and RDS connection identifiers. Such exposure effectively bypasses network namespace boundaries, which are intended to provide isolation between different virtualized or containerized environments, thereby compromising the confidentiality of inter-process communication states across isolated contexts.
From a security standards perspective, this vulnerability aligns with CWE-200: Information Exposure, as it allows an unauthorized actor to gain access to sensitive system information that should be restricted by administrative boundaries. Furthermore, the exploitation technique corresponds to ATT&CK T1083: File and Directory Discovery, where the attacker enumerates available resources to map out the network landscape of the host. The ability to read socket inodes and sequence numbers also poses a risk for further attacks, such as session hijacking or traffic analysis, if an adversary can correlate these identifiers with actual data flows. The vulnerability persists because the kernel does not enforce namespace-aware filtering on the RDS control plane, treating all sockets as globally visible regardless of their network context.
The resolution involves modifying the rds_info_getsockopt logic to perform strict netns matching before copying any socket or connection information to user space. For each entry in the global lists, the handler now compares the network namespace of the caller's socket against the network namespace associated with the list entry. If they do not match, the entry is skipped. This ensures that processes only see resources belonging to their own network namespace. Additionally, aggregate counters like RDS_INFO_COUNTERS remain accessible globally as they represent system-wide statistics rather than per-namespace state. The fix also removes obsolete global counter variables such as rds_sock_count and rds_tcp_tc_count, which were previously used for size prechecks but are no longer needed after the implementation of a per-namespace counting mechanism during list traversal. This cleanup eliminates redundant code paths and reduces the attack surface by removing unnecessary global state management logic that could potentially be exploited in other contexts.