CVE-2024-46858 (Moderate severity, published 2024-09-26)
CVSS score: 7 (CVSS:3.1/AV:L/AC:H/PR:L/UI:N/S:U/C:H/I:H/A:H)
CWE: CWE-416
Description: In the Linux kernel, the following vulnerability has been resolved:

mptcp: pm: Fix uaf in __timer_delete_sync

There are two paths to access mptcp_pm_del_add_timer, result in a race
condition:

     CPU1				CPU2
     ====                               ====
     net_rx_action
     napi_poll                          netlink_sendmsg
     __napi_poll                        netlink_unicast
     process_backlog                    netlink_unicast_kernel
     __netif_receive_skb                genl_rcv
     __netif_receive_skb_one_core       netlink_rcv_skb
     NF_HOOK                            genl_rcv_msg
     ip_local_deliver_finish            genl_family_rcv_msg
     ip_protocol_deliver_rcu            genl_family_rcv_msg_doit
     tcp_v4_rcv                         mptcp_pm_nl_flush_addrs_doit
     tcp_v4_do_rcv                      mptcp_nl_remove_addrs_list
     tcp_rcv_established                mptcp_pm_remove_addrs_and_subflows
     tcp_data_queue                     remove_anno_list_by_saddr
     mptcp_incoming_options             mptcp_pm_del_add_timer
     mptcp_pm_del_add_timer             kfree(entry)

In remove_anno_list_by_saddr(running on CPU2), after leaving the critical
zone protected by "pm.lock", the entry will be released, which leads to the
occurrence of uaf in the mptcp_pm_del_add_timer(running on CPU1).

Keeping a reference to add_timer inside the lock, and calling
sk_stop_timer_sync() with this reference, instead of "entry->add_timer".

Move list_del(&entry->list) to mptcp_pm_del_add_timer and inside the pm lock,
do not directly access any members of the entry outside the pm lock, which
can avoid similar "entry->x" uaf.
Statement: Actual only for latest version of Red Hat Enterprise Linux 9 and latest version of Red Hat Enterprise Linux 8.

Within regulated environments, a combination of the following controls acts as a significant barrier to successfully exploiting a CWE-416: Use After Free vulnerability and therefore downgrades the severity of this particular CVE from Moderate to Low.

Access to the platform is granted only after successful hard token-based multi-factor authentication (MFA) and is governed by least privilege to ensure that only authorized users and roles can execute or modify code. Red Hat also enforces least functionality, enabling only essential features, services, and ports. Hardening guidelines ensure the most restrictive settings required for operations, while baseline configurations enforce safe memory allocation and deallocation practices to reduce the risk of use-after-free vulnerabilities. The environment employs IPS/IDS and antimalware solutions to detect and prevent malicious code and provide real-time visibility into memory usage, lowering the risk of arbitrary code execution. Static code analysis and peer reviews enforce strong input validation and error handling, reducing the likelihood of denial-of-service (DoS) attacks. In the event of successful exploitation, process isolation prevents a compromised process from accessing memory freed by another, containing potential impact. Finally, memory protection mechanisms such as Data Execution Prevention (DEP) and Address Space Layout Randomization (ASLR) enhance resilience against memory-related vulnerabilities.