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CVE-2023-31248 is a Linux kernel nftables vulnerability caused by missing activity-state validation in nft_chain_lookup_byid(). The function failed to verify that a chain was active for the current generation mask before returning it. As a result, within a single nftables batch transaction, a rule could reference a chain that had already been deleted and marked inactive. The vulnerable sequence described in the supporting content is: create a chain, delete that chain, create another chain, then add a jump/goto rule that references the deleted chain by chain ID. Because the inactive chain could still be looked up, its reference count could be incremented and later manipulated in a way that leaves stale references. The issue can be turned into a use-after-free by racing rule deletion in the control plane against asynchronous transaction cleanup in nf_tables_trans_destroy_work, so that the chain object is freed while a stale rule still references it. The provided analysis states the flaw was exploited on Ubuntu 23.04 with kernel 6.2.0-20-generic and affects Linux kernel versions before 6.2.0-26-generic. The upstream fix adds genmask-based active-state validation to nft_chain_lookup_byid() and updates callers such as nf_tables_newrule and nft_verdict_init accordingly.
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A vulnerability listed as fixed by a SUSE security update affecting kernel-related packages; no further technical detail is provided in the content.
A vulnerability referenced in a SUSE security update advisory; no further technical detail is provided in the content.
Kernel vulnerability referenced in a SUSE security update advisory; no per-CVE technical details are provided in the content.
A Linux kernel nftables vulnerability caused by nft_chain_lookup_byid failing to verify whether a chain is active via genmask checks, enabling reference to an inactive/deleted chain and forming the basis for a use-after-free privilege escalation exploit.
Query your assets running an affected version, and investigate the blast radius.
Every observed campaign linking this CVE to a named adversary.
Malware families riding this exploit, with evidence and IOCs.
YARA, Sigma, Snort, and vendor rules, auto-deployed to your SIEM.
Cross-references every affected SKU, including bundled OEM variants.
Community discussion across Reddit, Mastodon, and other social sources.