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CVE PROGRAM SOURCE RECORD7.5 High

CVE-2026-72418

netfilter: nf_conncount: prevent connlimit drops for early confirmed ct

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Status
Published
Published
Updated
Assigning organization
Linux

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.

Affected products

Version statuses are supplied by the assigning organization. Consult the original record for detailed ranges and platform conditions.

Linux Linux

Default version status: unaffected

  • 460c112e1d887b58b06b56e8e0230058906ff2c3 to < 000ac6830b56499d6b65fd91486ce6689eb02be4affected
  • 53bc0ac47f4f7621c991807bc90e01df49561ac8 to < cbe2d14a7c5b1fc71821fbfee5c4963917411e92affected
  • ca8b4d1d6304a84ce2016fa2fe9a114b9607b839 to < 3793d24de224943e0a6016bbeffb6f5c4cea2e3daffected
  • 8286c02fe9100330475331253fc590f047963f90 to < abef7f817217fcb62c11821d6b895063eadb2828affected
  • b29ddccf36946a90323486221f39e9f88cc01b8e to < ebfe8249ba79e4ff0f1e3aad8787b992ef27f026affected
  • 77ea3d8ac3d3d59b5ac9ad639e4ba107c0f2ff1e to < 329f2626ee5cb8fafdf6b58b624311529c57cb45affected
  • 69894e5b4c5e28cda5f32af33d4a92b7a4b93b0e to < be52572c6d55f677ba76869d3c63805c0d4891a3affected
  • 69894e5b4c5e28cda5f32af33d4a92b7a4b93b0e to < c8b6f36f766991e3ebebec6596daee4b04dcbc49affected
  • f85623af16b83615e5f64a9b19ae1d584805cb07affected
  • 5.10.248 to < 5.10.261affected
  • 5.15.198 to < 5.15.212affected
  • 6.1.160 to < 6.1.178affected
  • 6.6.120 to < 6.6.145affected
  • 6.12.63 to < 6.12.97affected
  • 6.18.2 to < 6.18.40affected
  • 6.17.13 to < 6.18affected

Linux Linux

Default version status: affected

  • 6.19affected
  • 0 to < 6.19unaffected
  • 5.10.261 to ≤ 5.10.*unaffected
  • 5.15.212 to ≤ 5.15.*unaffected
  • 6.1.178 to ≤ 6.1.*unaffected
  • 6.6.145 to ≤ 6.6.*unaffected
  • 6.12.97 to ≤ 6.12.*unaffected
  • 6.18.40 to ≤ 6.18.*unaffected
  • 7.1.5 to ≤ 7.1.*unaffected
  • 7.2 to ≤ *unaffected

References