CVE-2026-68335
HighCVSS 7.8Exploitation Probability (EPSS)
Low risk3th percentile - higher than 3% of all known CVEs
Summary
A vulnerability was found in the Linux kernel's RDS (Reliable Datagram Sockets) subsystem. The destination socket lookup does not consider network namespaces, allowing a message to be delivered to a socket in a different namespace. This can lead to a use-after-free condition when the namespace is torn down, potentially causing a system crash or arbitrary code execution.
Risk Assessment
The vulnerability can be exploited by an unprivileged user (with user namespaces) to cause a kernel crash (DoS) or potentially escalate privileges. The attack requires the ability to create network namespaces, which has been available since kernel 3.8.
Recommendation
Apply the official Linux kernel patch that rejects messages crossing network namespace boundaries as soon as possible. If the patch is not yet available, restrict access to namespace creation (e.g., via sysctl kernel.unprivileged_userns_clone=0) and monitor the system for unusual activity.
Original NVD description (English source)
In the Linux kernel, the following vulnerability has been resolved: rds: drop incoming messages that cross network namespace boundaries rds_find_bound() looks up the destination socket using a global rhashtable keyed solely on (addr, port, scope_id). Network namespaces are not part of the key, so a sender in netns A can deliver an incoming message (inc) to a socket that lives in a different netns B. When this happens, inc->i_conn points to an rds_connection whose c_net is netns A, but the receiving rs lives in netns B. Once the child process that created netns A exits, cleanup_net() calls rds_loop_exit_net() -> rds_loop_kill_conns() -> rds_conn_destroy(), freeing that connection. If the survivor socket in netns B still holds the inc, any subsequent dereference of inc->i_conn is a use-after-free. There are two dangerous sites in rds_clear_recv_queue(): 1. inc->i_conn->c_lcong (offset 88 of freed rds_connection, size 200) read via rds_recv_rcvbuf_delta() -- confirmed by KASAN. 2. inc->i_conn->c_trans->inc_free(inc) (function pointer at offset 80) called via rds_inc_put() when the inc refcount reaches zero -- same race window, potential call-through-freed-object primitive. The bug is reachable from unprivileged user namespaces (CLONE_NEWUSER + CLONE_NEWNET), available since Linux 3.8. Fix this by rejecting the delivery in rds_recv_incoming() when the socket returned by rds_find_bound() belongs to a different network namespace than the connection that carried the message. Use the existing rds_conn_net() / sock_net() helpers and net_eq() for the comparison.