CVE-2023-53635
HighCVSS 8.2Exploitation Probability (EPSS)
Low risk32th percentile - higher than 32% of all known CVEs
Summary
In the Linux kernel, the netfilter conntrack module has an error in calculating the ct->timeout value. For unconfirmed connections, this value is incorrectly modified (adding/subtracting nfct_time_stamp), leading to incorrect timeout values.
Risk Assessment
Incorrect timeout values may cause firewall issues, including premature connection termination or uncontrolled persistence, potentially affecting service availability.
Recommendation
Update the Linux kernel to a version containing the fix that separates the cases of setting and reading ct->timeout.
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Original NVD description (English source)
In the Linux kernel, the following vulnerability has been resolved: netfilter: conntrack: fix wrong ct->timeout value (struct nf_conn)->timeout is an interval before the conntrack confirmed. After confirmed, it becomes a timestamp. It is observed that timeout of an unconfirmed conntrack: - Set by calling ctnetlink_change_timeout(). As a result, `nfct_time_stamp` was wrongly added to `ct->timeout` twice. - Get by calling ctnetlink_dump_timeout(). As a result, `nfct_time_stamp` was wrongly subtracted. Call Trace: <TASK> dump_stack_lvl ctnetlink_dump_timeout __ctnetlink_glue_build ctnetlink_glue_build __nfqnl_enqueue_packet nf_queue nf_hook_slow ip_mc_output ? __pfx_ip_finish_output ip_send_skb ? __pfx_dst_output udp_send_skb udp_sendmsg ? __pfx_ip_generic_getfrag sock_sendmsg Separate the 2 cases in: - Setting `ct->timeout` in __nf_ct_set_timeout(). - Getting `ct->timeout` in ctnetlink_dump_timeout(). Pablo appends: Update ctnetlink to set up the timeout _after_ the IPS_CONFIRMED flag is set on, otherwise conntrack creation via ctnetlink breaks. Note that the problem described in this patch occurs since the introduction of the nfnetlink_queue conntrack support, select a sufficiently old Fixes: tag for -stable kernel to pick up this fix.

