{ "dataType": "CVE_RECORD", "dataVersion": "5.2", "cveMetadata": { "cveId": "CVE-2026-72418", "assignerOrgId": "416baaa9-dc9f-4396-8d5f-8c081fb06d67", "state": "PUBLISHED", "assignerShortName": "Linux", "dateReserved": "2026-08-09T03:40:39.927Z", "datePublished": "2026-08-15T05:56:38.374Z", "dateUpdated": "2026-08-17T05:43:58.352Z" }, "containers": { "cna": { "providerMetadata": { "orgId": "416baaa9-dc9f-4396-8d5f-8c081fb06d67", "shortName": "Linux", "dateUpdated": "2026-08-17T05:43:58.352Z" }, "descriptions": [ { "lang": "en", "value": "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." } ], "metrics": [ { "cvssV3_1": { "version": "3.1", "vectorString": "CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:N/I:N/A:H", "baseScore": 7.5, "baseSeverity": "HIGH" }, "scenarios": [ { "lang": "en", "value": "AV:N - Exploitation is triggered by remote TCP packets processed through netfilter INPUT/FORWARD hooks (xt_connlimit, nft_connlimit, OVS ct-limit) that call nf_conncount_count_skb() on received skbs; no local syscall or ioctl is required.\nAC:L - An unauthenticated remote attacker can reliably trigger the bug by rapidly reconnecting to reuse a TIME_WAIT 4-tuple, a normal TCP behavior they fully control; no race against unrelated system events is required.\nPR:N - The attacker needs no privileges on the victim host; only inbound network access to a service protected by admin-configured connlimit rules is required, and no CAP_NET_ADMIN or namespace capabilities are needed to trigger the faulty counting path.\nUI:N - No victim user action is required; exploitation is achieved solely by sending crafted connection patterns over the network to a host already running connlimit enforcement.\nS:U - Impact is confined to incorrect netfilter connection accounting and packet drops within the same kernel/network security domain; there is no cross-boundary escape such as VM breakout or privilege escalation.\nC:N - The flaw is a connection-count bookkeeping error and premature garbage collection; it does not read kernel memory, leak data, or involve any memory corruption primitive.\nI:N - No unauthorized modification of data or code occurs; the only effect is dropping or mis-evaluating packets against connlimit policy, which is an availability concern rather than integrity compromise.\nA:H - When the miscount drives the connection count to zero, xt_connlimit hot-drops valid packets, falsely rejecting legitimate new connections and causing repeatable denial of service against protected services without authentication." } ] } ], "affected": [ { "product": "Linux", "vendor": "Linux", "defaultStatus": "unaffected", "repo": "https://git.kernel.org/pub/scm/linux/kernel/git/stable/linux.git", "programFiles": [ "net/netfilter/nf_conncount.c" ], "versions": [ { "version": "460c112e1d887b58b06b56e8e0230058906ff2c3", "lessThan": "000ac6830b56499d6b65fd91486ce6689eb02be4", "status": "affected", "versionType": "git" }, { "version": "53bc0ac47f4f7621c991807bc90e01df49561ac8", "lessThan": "cbe2d14a7c5b1fc71821fbfee5c4963917411e92", "status": "affected", "versionType": "git" }, { "version": "ca8b4d1d6304a84ce2016fa2fe9a114b9607b839", "lessThan": "3793d24de224943e0a6016bbeffb6f5c4cea2e3d", "status": "affected", "versionType": "git" }, { "version": "8286c02fe9100330475331253fc590f047963f90", "lessThan": "abef7f817217fcb62c11821d6b895063eadb2828", "status": "affected", "versionType": "git" }, { "version": "b29ddccf36946a90323486221f39e9f88cc01b8e", "lessThan": "ebfe8249ba79e4ff0f1e3aad8787b992ef27f026", "status": "affected", "versionType": "git" }, { "version": "77ea3d8ac3d3d59b5ac9ad639e4ba107c0f2ff1e", "lessThan": "329f2626ee5cb8fafdf6b58b624311529c57cb45", "status": "affected", "versionType": "git" }, { "version": "69894e5b4c5e28cda5f32af33d4a92b7a4b93b0e", "lessThan": "be52572c6d55f677ba76869d3c63805c0d4891a3", "status": "affected", "versionType": "git" }, { "version": "69894e5b4c5e28cda5f32af33d4a92b7a4b93b0e", "lessThan": "c8b6f36f766991e3ebebec6596daee4b04dcbc49", "status": "affected", "versionType": "git" }, { "version": "f85623af16b83615e5f64a9b19ae1d584805cb07", "status": "affected", "versionType": "git" }, { "version": "5.10.248", "lessThan": "5.10.261", "status": "affected", "versionType": "semver" }, { "version": "5.15.198", "lessThan": "5.15.212", "status": "affected", "versionType": "semver" }, { "version": "6.1.160", "lessThan": "6.1.178", "status": "affected", "versionType": "semver" }, { "version": "6.6.120", "lessThan": "6.6.145", "status": "affected", "versionType": "semver" }, { "version": "6.12.63", "lessThan": "6.12.97", "status": "affected", "versionType": "semver" }, { "version": "6.18.2", "lessThan": "6.18.40", "status": "affected", "versionType": "semver" }, { "version": "6.17.13", "lessThan": "6.18", "status": "affected", "versionType": "semver" } ] }, { "product": "Linux", "vendor": "Linux", "defaultStatus": "affected", "repo": "https://git.kernel.org/pub/scm/linux/kernel/git/stable/linux.git", "programFiles": [ "net/netfilter/nf_conncount.c" ], "versions": [ { "version": "6.19", "status": "affected" }, { "version": "0", "lessThan": "6.19", "status": "unaffected", "versionType": "semver" }, { "version": "5.10.261", "lessThanOrEqual": "5.10.*", "status": "unaffected", "versionType": "semver" }, { "version": "5.15.212", "lessThanOrEqual": "5.15.*", "status": "unaffected", "versionType": "semver" }, { "version": "6.1.178", "lessThanOrEqual": "6.1.*", "status": "unaffected", "versionType": "semver" }, { "version": "6.6.145", "lessThanOrEqual": "6.6.*", "status": "unaffected", "versionType": "semver" }, { "version": "6.12.97", "lessThanOrEqual": "6.12.*", "status": "unaffected", "versionType": "semver" }, { "version": "6.18.40", "lessThanOrEqual": "6.18.*", "status": "unaffected", "versionType": "semver" }, { "version": "7.1.5", "lessThanOrEqual": "7.1.*", "status": "unaffected", "versionType": "semver" }, { "version": "7.2", "lessThanOrEqual": "*", "status": "unaffected", "versionType": "original_commit_for_fix" } ] } ], "cpeApplicability": [ { "nodes": [ { "operator": "OR", "negate": false, "cpeMatch": [ { "vulnerable": true, "criteria": "cpe:2.3:o:linux:linux_kernel:*:*:*:*:*:*:*:*", "versionStartIncluding": "5.10.248", "versionEndExcluding": "5.10.261" }, { "vulnerable": true, "criteria": "cpe:2.3:o:linux:linux_kernel:*:*:*:*:*:*:*:*", "versionStartIncluding": "5.15.198", "versionEndExcluding": "5.15.212" }, { "vulnerable": true, "criteria": "cpe:2.3:o:linux:linux_kernel:*:*:*:*:*:*:*:*", "versionStartIncluding": "6.1.160", "versionEndExcluding": "6.1.178" }, { "vulnerable": true, "criteria": "cpe:2.3:o:linux:linux_kernel:*:*:*:*:*:*:*:*", "versionStartIncluding": "6.6.120", "versionEndExcluding": "6.6.145" }, { "vulnerable": true, "criteria": "cpe:2.3:o:linux:linux_kernel:*:*:*:*:*:*:*:*", "versionStartIncluding": "6.12.63", "versionEndExcluding": "6.12.97" }, { "vulnerable": true, "criteria": "cpe:2.3:o:linux:linux_kernel:*:*:*:*:*:*:*:*", "versionStartIncluding": "6.18.2", "versionEndExcluding": "6.18.40" }, { "vulnerable": true, "criteria": "cpe:2.3:o:linux:linux_kernel:*:*:*:*:*:*:*:*", "versionStartIncluding": "6.19", "versionEndExcluding": "7.1.5" }, { "vulnerable": true, "criteria": "cpe:2.3:o:linux:linux_kernel:*:*:*:*:*:*:*:*", "versionStartIncluding": "6.19", "versionEndExcluding": "7.2" }, { "vulnerable": true, "criteria": "cpe:2.3:o:linux:linux_kernel:*:*:*:*:*:*:*:*", "versionStartIncluding": "6.17.13" } ] } ] } ], "references": [ { "url": "https://git.kernel.org/stable/c/000ac6830b56499d6b65fd91486ce6689eb02be4" }, { "url": "https://git.kernel.org/stable/c/cbe2d14a7c5b1fc71821fbfee5c4963917411e92" }, { "url": "https://git.kernel.org/stable/c/3793d24de224943e0a6016bbeffb6f5c4cea2e3d" }, { "url": "https://git.kernel.org/stable/c/abef7f817217fcb62c11821d6b895063eadb2828" }, { "url": "https://git.kernel.org/stable/c/ebfe8249ba79e4ff0f1e3aad8787b992ef27f026" }, { "url": "https://git.kernel.org/stable/c/329f2626ee5cb8fafdf6b58b624311529c57cb45" }, { "url": "https://git.kernel.org/stable/c/be52572c6d55f677ba76869d3c63805c0d4891a3" }, { "url": "https://git.kernel.org/stable/c/c8b6f36f766991e3ebebec6596daee4b04dcbc49" } ], "title": "netfilter: nf_conncount: prevent connlimit drops for early confirmed ct", "x_generator": { "engine": "bippy-1.2.0" } } } }