CVE-2026-72418
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.
How to fix
- Linux Linux000ac6830b56499d6b65fd91486ce6689eb02be4, cbe2d14a7c5b1fc71821fbfee5c4963917411e92, 3793d24de224943e0a6016bbeffb6f5c4cea2e3d, abef7f817217fcb62c11821d6b895063eadb2828, ebfe8249ba79e4ff0f1e3aad8787b992ef27f026, 329f2626ee5cb8fafdf6b58b624311529c57cb45, be52572c6d55f677ba76869d3c63805c0d4891a3, c8b6f36f766991e3ebebec6596daee4b04dcbc49, 5.10.261, 5.15.212, 6.1.178, 6.6.145, 6.12.97, 6.18.40, 6.18 or later
Affected products
| Product | Affected versions | Fixed in |
|---|---|---|
| Linux Linux | 460c112e1d887b58b06b56e8e0230058906ff2c3 ≤ v < 000ac6830b56499d6b65fd91486ce6689eb02be4, 53bc0ac47f4f7621c991807bc90e01df49561ac8 ≤ v < cbe2d14a7c5b1fc71821fbfee5c4963917411e92, ca8b4d1d6304a84ce2016fa2fe9a114b9607b839 ≤ v < 3793d24de224943e0a6016bbeffb6f5c4cea2e3d, 8286c02fe9100330475331253fc590f047963f90 ≤ v < abef7f817217fcb62c11821d6b895063eadb2828, b29ddccf36946a90323486221f39e9f88cc01b8e ≤ v < ebfe8249ba79e4ff0f1e3aad8787b992ef27f026, 77ea3d8ac3d3d59b5ac9ad639e4ba107c0f2ff1e ≤ v < 329f2626ee5cb8fafdf6b58b624311529c57cb45, 69894e5b4c5e28cda5f32af33d4a92b7a4b93b0e ≤ v < be52572c6d55f677ba76869d3c63805c0d4891a3, 69894e5b4c5e28cda5f32af33d4a92b7a4b93b0e ≤ v < c8b6f36f766991e3ebebec6596daee4b04dcbc49, f85623af16b83615e5f64a9b19ae1d584805cb07, 5.10.248 ≤ v < 5.10.261, 5.15.198 ≤ v < 5.15.212, 6.1.160 ≤ v < 6.1.178, 6.6.120 ≤ v < 6.6.145, 6.12.63 ≤ v < 6.12.97, 6.18.2 ≤ v < 6.18.40, 6.17.13 ≤ v < 6.18, 6.19 | 000ac6830b56499d6b65fd91486ce6689eb02be4, cbe2d14a7c5b1fc71821fbfee5c4963917411e92, 3793d24de224943e0a6016bbeffb6f5c4cea2e3d, abef7f817217fcb62c11821d6b895063eadb2828, ebfe8249ba79e4ff0f1e3aad8787b992ef27f026, 329f2626ee5cb8fafdf6b58b624311529c57cb45, be52572c6d55f677ba76869d3c63805c0d4891a3, c8b6f36f766991e3ebebec6596daee4b04dcbc49, 5.10.261, 5.15.212, 6.1.178, 6.6.145, 6.12.97, 6.18.40, 6.18 |
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