CVE-2023-53619: netfilter: conntrack: Avoid nf_ct_helper_hash uses after free

Severity: high (CVSS 7.8 v3.1)
Exploited in the wild: not listed in CISA KEV
EPSS: 0.2% probability of exploitation in the next 30 days
Public exploit or detection template: none known
Published: 2025-10-07 · updated 2026-10-15
Weakness: CWE-416

Description

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.

Affected products

Linux kernel: from 3.6 before 4.14.322; from 4.15 before 4.19.291; from 4.20 before 5.4.251; from 5.5 before 5.10.188; from 5.11 before 5.15.121; from 5.16 before 6.1.39 — fixed in 4.14.322, 4.19.291, 5.10.188, 5.15.121, 5.4.251, 6.1.39

How to fix

Upgrade to a fixed version: Linux kernel 4.14.322, 4.19.291, 5.10.188, 5.15.121. Check the vendor advisory for mitigations.

References

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