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.

Gravité et risque d'exploitation

CVE-2026-72418 obtient un score CVSS de 7.5/10, soit une gravité élevée. Selon le modèle EPSS, la probabilité qu'elle soit exploitée dans les 30 prochains jours est de 0.72 %, ce qui la place devant 52.9 % des CVE référencées.

Que faire ?

• Vérifiez si Linux (versions <=6.1.*, 7.1.5, 6.18.40, <=6.12.*, <6.19, 6.18.2, 69894e5b4c5e28cda5f32af33d4a92b7a4b93b0e, 6.1.160, <5.15.212, 0, <cbe2d14a7c5b1fc71821fbfee5c4963917411e92, ca8b4d1d6304a84ce2016fa2fe9a114b9607b839, <abef7f817217fcb62c11821d6b895063eadb2828, <=7.1.*, 6.6.120, 460c112e1d887b58b06b56e8e0230058906ff2c3, <3793d24de224943e0a6016bbeffb6f5c4cea2e3d, 6.17.13, 5.15.198, <be52572c6d55f677ba76869d3c63805c0d4891a3, 6.1.178, <=5.10.*, <=6.6.*, <ebfe8249ba79e4ff0f1e3aad8787b992ef27f026, 6.12.97, <6.1.178, <000ac6830b56499d6b65fd91486ce6689eb02be4, b29ddccf36946a90323486221f39e9f88cc01b8e, 53bc0ac47f4f7621c991807bc90e01df49561ac8, <6.18.40, <=6.18.*, 5.15.212, 6.12.63, 6.6.145, 5.10.261, <c8b6f36f766991e3ebebec6596daee4b04dcbc49, <5.10.261, 77ea3d8ac3d3d59b5ac9ad639e4ba107c0f2ff1e, 5.10.248, <6.18, <6.6.145, <=*, <=5.15.*, 6.19, <329f2626ee5cb8fafdf6b58b624311529c57cb45, <6.12.97, f85623af16b83615e5f64a9b19ae1d584805cb07, 7.2, 8286c02fe9100330475331253fc590f047963f90) est présent sur votre parc.
• Appliquez le correctif ou la version corrigée indiqués dans les références de l'éditeur.
• À défaut de correctif, limitez l'exposition (filtrage réseau, désactivation du composant).
• Automatisez la détection : les agents CVE Heimdall (gratuits, open source) corrèlent l'inventaire de vos serveurs avec la base CVE.

Références

• https://git.kernel.org/stable/c/000ac6830b56499d6b65fd91486ce6689eb02be4
• https://git.kernel.org/stable/c/cbe2d14a7c5b1fc71821fbfee5c4963917411e92
• https://git.kernel.org/stable/c/3793d24de224943e0a6016bbeffb6f5c4cea2e3d
• https://git.kernel.org/stable/c/abef7f817217fcb62c11821d6b895063eadb2828
• https://git.kernel.org/stable/c/ebfe8249ba79e4ff0f1e3aad8787b992ef27f026
• https://git.kernel.org/stable/c/329f2626ee5cb8fafdf6b58b624311529c57cb45
• https://git.kernel.org/stable/c/be52572c6d55f677ba76869d3c63805c0d4891a3
• https://git.kernel.org/stable/c/c8b6f36f766991e3ebebec6596daee4b04dcbc49