CVE-2023-53619

In the Linux kernel, the following vulnerability has been resolved:

netfilter: conntrack: Avoid nf_ct_helper_hash uses after free

If nf_conntrack_init_start() fails (for example due to a register_nf_conntrack_bpf() failure), the nf_conntrack_helper_fini() clean-up path frees the nf_ct_helper_hash map.

When built with NF_CONNTRACK=y, further netfilter modules (e.g: netfilter_conntrack_ftp) can still be loaded and call nf_conntrack_helpers_register(), independently of whether nf_conntrack initialized correctly. This accesses the nf_ct_helper_hash dangling pointer and causes a uaf, possibly leading to random memory corruption.

This patch guards nf_conntrack_helper_register() from accessing a freed or uninitialized nf_ct_helper_hash pointer and fixes possible uses-after-free when loading a conntrack module.

A UAF in netfilter conntrack helpers could occur if nf_conntrack init fails and helper modules are loaded afterward, dereferencing the freed nf_ct_helper_hash. The fix guards registration when the table is absent and NULLs it on teardown. For the CVSS the PR:H because exploitation requires module management / kernel privileges (loading helpers or inducing init failure), so typical exposure is to privileged local actors.

The CVSS score(s) listed for this vulnerability do not reflect the associated product's status, and are included for informational purposes to better understand the severity of this vulnerability.