CVE-2026-72418
In the Linux kernel, the following vulnerability has been resolved: netfilter: nf_conncount: prevent connlimit drops for early confirmed ct Commit 69894e5b4c5e ("netfilter: nft_connlimit: update the count if add was skipped") introduced a regression…
Does this matter?
High impact if exploited, but EPSS currently rates exploitation as unlikely (0.71%). Schedule it in the normal patch cycle and watch for a rise in EPSS or a public exploit.
Description
In the Linux kernel, the following vulnerability has been resolved: netfilter: nf_conncount: prevent connlimit drops for early confirmed ct Commit 69894e5b4c5e ("netfilter: nft_connlimit: update the count if add was skipped") introduced a regression where packets for valid connections are dropped when using connlimit for soft-limiting scenarios. The issue occurs when a new connection reuses a socket currently in the TIME_WAIT state. In this scenario, the connection tracking entry is evaluated as already confirmed. Previously, __nf_conncount_add() assumed that if a connection was confirmed and did not originate from the loopback interface, it should skip the addition and return -EEXIST. Skipping the addition triggers a garbage collection run that cleans up the TIME_WAIT connection. Consequently, the active connection count drops to 0, which xt_connlimit mishandles, leading to the false rejection of the perfectly valid new connection. Fix this by replacing the interface check with protocol-agnostic state checks. We now skip the tree insertion and preserve the lockless garbage collection optimization only if the connection is IPS_ASSURED. This allows early-confirmed setup packets (such as reused TIME_WAIT sockets or locally generated SYN-ACKs) to be properly evaluated and counted without falsely dropping. The goto check_connections path is maintained to ensure these setup packets are deduplicated correctly. This has been tested with slowhttptest and HTTP server configured locally to ensure we are not breaking soft-limiting scenarios for local or external connections. In addition, it was tested with a OVS zone limit too.
- CVSS 3.1
- 7.5 HIGHCVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:N/I:N/A:H
- EPSS
- 0.71% probability · 51th percentile
- CISA KEV
- Not listed
- Source
- 416baaa9-dc9f-4396-8d5f-8c081fb06d67
References
- https://git.kernel.org/stable/c/000ac6830b56499d6b65fd91486ce6689eb02be4
- https://git.kernel.org/stable/c/329f2626ee5cb8fafdf6b58b624311529c57cb45
- https://git.kernel.org/stable/c/3793d24de224943e0a6016bbeffb6f5c4cea2e3d
- https://git.kernel.org/stable/c/abef7f817217fcb62c11821d6b895063eadb2828
- https://git.kernel.org/stable/c/be52572c6d55f677ba76869d3c63805c0d4891a3
- https://git.kernel.org/stable/c/c8b6f36f766991e3ebebec6596daee4b04dcbc49
- https://git.kernel.org/stable/c/cbe2d14a7c5b1fc71821fbfee5c4963917411e92
- https://git.kernel.org/stable/c/ebfe8249ba79e4ff0f1e3aad8787b992ef27f026
Source: NVD record, EPSS from FIRST.org, KEV from CISA. Refreshed daily.