GHSA-PRXP-6XJX-9QX5
Vulnerability from github – Published: 2026-08-15 06:32 – Updated: 2026-08-17 06:33In 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": [],
"aliases": [
"CVE-2026-72418"
],
"database_specific": {
"cwe_ids": [],
"github_reviewed": false,
"github_reviewed_at": null,
"nvd_published_at": "2026-08-15T06:22:15Z",
"severity": "HIGH"
},
"details": "In the Linux kernel, the following vulnerability has been resolved:\n\nnetfilter: nf_conncount: prevent connlimit drops for early confirmed ct\n\nCommit 69894e5b4c5e (\"netfilter: nft_connlimit: update the count if add\nwas skipped\") introduced a regression where packets for valid\nconnections are dropped when using connlimit for soft-limiting\nscenarios.\n\nThe issue occurs when a new connection reuses a socket currently in\nthe TIME_WAIT state. In this scenario, the connection tracking entry\nis evaluated as already confirmed. Previously, __nf_conncount_add()\nassumed that if a connection was confirmed and did not originate from\nthe loopback interface, it should skip the addition and return -EEXIST.\n\nSkipping the addition triggers a garbage collection run that cleans up\nthe TIME_WAIT connection. Consequently, the active connection count\ndrops to 0, which xt_connlimit mishandles, leading to the false rejection\nof the perfectly valid new connection.\n\nFix this by replacing the interface check with protocol-agnostic state\nchecks. We now skip the tree insertion and preserve the lockless garbage\ncollection optimization only if the connection is IPS_ASSURED. This\nallows early-confirmed setup packets (such as reused TIME_WAIT sockets\nor locally generated SYN-ACKs) to be properly evaluated and counted\nwithout falsely dropping. The goto check_connections path is maintained\nto ensure these setup packets are deduplicated correctly.\n\nThis has been tested with slowhttptest and HTTP server configured\nlocally to ensure we are not breaking soft-limiting scenarios for local\nor external connections. In addition, it was tested with a OVS zone\nlimit too.",
"id": "GHSA-prxp-6xjx-9qx5",
"modified": "2026-08-17T06:33:28Z",
"published": "2026-08-15T06:32:23Z",
"references": [
{
"type": "ADVISORY",
"url": "https://nvd.nist.gov/vuln/detail/CVE-2026-72418"
},
{
"type": "WEB",
"url": "https://git.kernel.org/stable/c/000ac6830b56499d6b65fd91486ce6689eb02be4"
},
{
"type": "WEB",
"url": "https://git.kernel.org/stable/c/329f2626ee5cb8fafdf6b58b624311529c57cb45"
},
{
"type": "WEB",
"url": "https://git.kernel.org/stable/c/3793d24de224943e0a6016bbeffb6f5c4cea2e3d"
},
{
"type": "WEB",
"url": "https://git.kernel.org/stable/c/abef7f817217fcb62c11821d6b895063eadb2828"
},
{
"type": "WEB",
"url": "https://git.kernel.org/stable/c/be52572c6d55f677ba76869d3c63805c0d4891a3"
},
{
"type": "WEB",
"url": "https://git.kernel.org/stable/c/c8b6f36f766991e3ebebec6596daee4b04dcbc49"
},
{
"type": "WEB",
"url": "https://git.kernel.org/stable/c/cbe2d14a7c5b1fc71821fbfee5c4963917411e92"
},
{
"type": "WEB",
"url": "https://git.kernel.org/stable/c/ebfe8249ba79e4ff0f1e3aad8787b992ef27f026"
}
],
"schema_version": "1.4.0",
"severity": [
{
"score": "CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:N/I:N/A:H",
"type": "CVSS_V3"
}
]
}
Sightings
| Author | Source | Type | Date | Other |
|---|
Nomenclature
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- Not confirmed: The user expressed doubt about the validity of the vulnerability.
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