Linux kernel: Netfilter nft_flow_offload ref leak on init failure
CVE-2026-98851 Published on October 18, 2026
netfilter: nft_flow_offload: drop flowtable reference on init error path
In the Linux kernel, the following vulnerability has been resolved:
netfilter: nft_flow_offload: drop flowtable reference on init error path
nft_flow_offload_init() bumps the flowtable use count with
nft_use_inc() before calling nf_ct_netns_get(). When the latter
fails, the error is returned as-is and the reference is leaked.
The upper layers do not balance it either: nf_tables_newexpr()
clears expr->ops when the expression init callback fails, so the
nft_expr_more() iteration in nft_rule_expr_deactivate() and
nf_tables_rule_destroy() stops right before the failed expression
and its ->destroy callback, which would drop the reference, never
runs.
Each failed rule addition therefore leaks one flowtable reference
and the flowtable can no longer be removed: NFT_MSG_DELFLOWTABLE
keeps reporting -EBUSY even though no rule references it.
Save the nf_ct_netns_get() return value and undo the nft_use_inc()
when it fails, restoring the inc/dec pairing within
nft_flow_offload_init() itself.
Products Associated with CVE-2026-98851
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Affected Versions
Linux:- Version a3c90f7a2323b331ae816d5b0633e68148e25d04 and below 64ac0cb574c740bf723affb79b646eeba920db6b is affected.
- Version a3c90f7a2323b331ae816d5b0633e68148e25d04 and below c5f91098edee98c015f78488460a0609e62582a5 is affected.
- Version a3c90f7a2323b331ae816d5b0633e68148e25d04 and below 4cd378423a33194a773c267fc58606d28fce95cf is affected.
- Version a3c90f7a2323b331ae816d5b0633e68148e25d04 and below 747928b5d4ff8c8de55138a54c13980e4bb88578 is affected.
- Version 4.16 is affected.
- Before 4.16 is unaffected.
- Version 6.12.113, <= 6.12.* is unaffected.
- Version 6.18.56, <= 6.18.* is unaffected.
- Version 7.2.10, <= 7.2.* is unaffected.
- Version 7.3-rc6, <= * is unaffected.