CVE-2026-74480 (GCVE-0-2026-74480)
Vulnerability from cvelistv5 – Published: 2026-08-15 12:27 – Updated: 2026-08-19 16:37
VLAI
EPSS
VEX
Title
net: bridge: stop fast-leave after deleting a port group
Summary
In the Linux kernel, the following vulnerability has been resolved:
net: bridge: stop fast-leave after deleting a port group
br_multicast_leave_group() iterates mp->ports with pp = &p->next in
its fast-leave path. After br_multicast_del_pg() removes p,
continuing the loop advances pp through the deleted entry.
If multicast-to-unicast was enabled, the bridge can hold multiple port
groups for the same port and group with different source MAC
addresses. Once multicast-to-unicast is disabled,
br_port_group_equal() matches those entries by port only. A fast leave
can then delete one entry and continue from its stale next pointer,
leaving mp->ports pointing at a deleted port group.
Fast leave only needs to remove one matching port group. Break after
br_multicast_del_pg() so the loop stops before dereferencing the
removed entry.
Severity
9.8 (Critical)
Assigner
References
8 references
Impacted products
2 products
| Vendor | Product | Version | CPE status | |
|---|---|---|---|---|
| Linux | Linux |
Affected:
6db6f0eae6052b70885562e1733896647ec1d807 , < d6c32e2e25a9a06ba021030e26b6d602a277eb72
(git)
Affected: 6db6f0eae6052b70885562e1733896647ec1d807 , < 482bcb85139addb4e8ac8ed10baeda3e0aad4031 (git) Affected: 6db6f0eae6052b70885562e1733896647ec1d807 , < 1a109cc9890d017c41d77e6c82da739579c49f0b (git) Affected: 6db6f0eae6052b70885562e1733896647ec1d807 , < 159ad90cb929c033308bb39a2c5f8fbf393b77aa (git) Affected: 6db6f0eae6052b70885562e1733896647ec1d807 , < 4695430e8132420bf8de94da3eb36a6cf35fde6b (git) Affected: 6db6f0eae6052b70885562e1733896647ec1d807 , < 0309ebbc570000ea0df11c06b69798e5860c5f6f (git) Affected: 6db6f0eae6052b70885562e1733896647ec1d807 , < 4c57056ca6aace2e9f94ae9298bf49ef6b0c95e4 (git) Affected: 6db6f0eae6052b70885562e1733896647ec1d807 , < a39789f211b8a4125f0c70e05b30cf715f4f187d (git) |
guessed | |
| Linux | Linux |
Affected:
4.11
Unaffected: 0 , < 4.11 (semver) Unaffected: 5.10.265 , ≤ 5.10.* (semver) Unaffected: 5.15.216 , ≤ 5.15.* (semver) Unaffected: 6.1.183 , ≤ 6.1.* (semver) Unaffected: 6.6.151 , ≤ 6.6.* (semver) Unaffected: 6.12.103 , ≤ 6.12.* (semver) Unaffected: 6.18.44 , ≤ 6.18.* (semver) Unaffected: 7.1.8 , ≤ 7.1.* (semver) Unaffected: 7.2 , ≤ * (original_commit_for_fix) |
guessed |
{
"containers": {
"cna": {
"affected": [
{
"defaultStatus": "unaffected",
"product": "Linux",
"programFiles": [
"net/bridge/br_multicast.c"
],
"repo": "https://git.kernel.org/pub/scm/linux/kernel/git/stable/linux.git",
"vendor": "Linux",
"versions": [
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"version": "6db6f0eae6052b70885562e1733896647ec1d807",
"versionType": "git"
},
{
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}
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},
{
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"programFiles": [
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],
"repo": "https://git.kernel.org/pub/scm/linux/kernel/git/stable/linux.git",
"vendor": "Linux",
"versions": [
{
"status": "affected",
"version": "4.11"
},
{
"lessThan": "4.11",
"status": "unaffected",
"version": "0",
"versionType": "semver"
},
{
"lessThanOrEqual": "5.10.*",
"status": "unaffected",
"version": "5.10.265",
"versionType": "semver"
},
{
"lessThanOrEqual": "5.15.*",
"status": "unaffected",
"version": "5.15.216",
"versionType": "semver"
},
{
"lessThanOrEqual": "6.1.*",
"status": "unaffected",
"version": "6.1.183",
"versionType": "semver"
},
{
"lessThanOrEqual": "6.6.*",
"status": "unaffected",
"version": "6.6.151",
"versionType": "semver"
},
{
"lessThanOrEqual": "6.12.*",
"status": "unaffected",
"version": "6.12.103",
"versionType": "semver"
},
{
"lessThanOrEqual": "6.18.*",
"status": "unaffected",
"version": "6.18.44",
"versionType": "semver"
},
{
"lessThanOrEqual": "7.1.*",
"status": "unaffected",
"version": "7.1.8",
"versionType": "semver"
},
{
"lessThanOrEqual": "*",
"status": "unaffected",
"version": "7.2",
"versionType": "original_commit_for_fix"
}
]
}
],
"cpeApplicability": [
{
"nodes": [
{
"cpeMatch": [
{
"criteria": "cpe:2.3:o:linux:linux_kernel:*:*:*:*:*:*:*:*",
"versionEndExcluding": "5.10.265",
"versionStartIncluding": "4.11",
"vulnerable": true
},
{
"criteria": "cpe:2.3:o:linux:linux_kernel:*:*:*:*:*:*:*:*",
"versionEndExcluding": "5.15.216",
"versionStartIncluding": "4.11",
"vulnerable": true
},
{
"criteria": "cpe:2.3:o:linux:linux_kernel:*:*:*:*:*:*:*:*",
"versionEndExcluding": "6.1.183",
"versionStartIncluding": "4.11",
"vulnerable": true
},
{
"criteria": "cpe:2.3:o:linux:linux_kernel:*:*:*:*:*:*:*:*",
"versionEndExcluding": "6.6.151",
"versionStartIncluding": "4.11",
"vulnerable": true
},
{
"criteria": "cpe:2.3:o:linux:linux_kernel:*:*:*:*:*:*:*:*",
"versionEndExcluding": "6.12.103",
"versionStartIncluding": "4.11",
"vulnerable": true
},
{
"criteria": "cpe:2.3:o:linux:linux_kernel:*:*:*:*:*:*:*:*",
"versionEndExcluding": "6.18.44",
"versionStartIncluding": "4.11",
"vulnerable": true
},
{
"criteria": "cpe:2.3:o:linux:linux_kernel:*:*:*:*:*:*:*:*",
"versionEndExcluding": "7.1.8",
"versionStartIncluding": "4.11",
"vulnerable": true
},
{
"criteria": "cpe:2.3:o:linux:linux_kernel:*:*:*:*:*:*:*:*",
"versionEndExcluding": "7.2",
"versionStartIncluding": "4.11",
"vulnerable": true
}
],
"negate": false,
"operator": "OR"
}
]
}
],
"descriptions": [
{
"lang": "en",
"value": "In the Linux kernel, the following vulnerability has been resolved:\n\nnet: bridge: stop fast-leave after deleting a port group\n\nbr_multicast_leave_group() iterates mp-\u003eports with pp = \u0026p-\u003enext in\nits fast-leave path. After br_multicast_del_pg() removes p,\ncontinuing the loop advances pp through the deleted entry.\n\nIf multicast-to-unicast was enabled, the bridge can hold multiple port\ngroups for the same port and group with different source MAC\naddresses. Once multicast-to-unicast is disabled,\nbr_port_group_equal() matches those entries by port only. A fast leave\ncan then delete one entry and continue from its stale next pointer,\nleaving mp-\u003eports pointing at a deleted port group.\n\nFast leave only needs to remove one matching port group. Break after\nbr_multicast_del_pg() so the loop stops before dereferencing the\nremoved entry."
}
],
"metrics": [
{
"cvssV3_1": {
"baseScore": 9.8,
"baseSeverity": "CRITICAL",
"vectorString": "CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:H/I:H/A:H",
"version": "3.1"
},
"scenarios": [
{
"lang": "en",
"value": "AV:N - The bug is reached when the bridge network stack processes attacker-supplied IGMP/MLD Leave packets received on a bridge port (br_handle_frame_finish -\u003e br_multicast_rcv -\u003e br_ip4/ip6_multicast_leave_group -\u003e br_multicast_leave_group), requiring no local syscall access.\nAC:L - Once a bridge has IGMP snooping, fast-leave, and leftover duplicate port groups (common on WiFi APs that used multicast-to-unicast), an attacker can reliably trigger the bug by sending IGMP/MLD joins then a Leave; no uncontrollable race or rare timing is required.\nPR:N - No privileges or authentication are required on the target; any host on an attached bridge port can inject IGMP/MLD Leave packets that are processed and reach the vulnerable fast-leave deletion loop.\nUI:N - Exploitation requires only attacker-sent multicast control packets; no victim user action such as opening files, clicking links, or mounting filesystems is needed.\nS:U - Impact is kernel heap corruption and use-after-free within the bridge/multicast subsystem on the same host; it does not cross a VM/hypervisor or IOMMU security boundary by itself.\nC:H - Deleting a port group then continuing the list walk dereferences freed net_bridge_port_group memory and can leave mp-\u003eports dangling, giving a use-after-free read primitive exploitable for arbitrary kernel memory disclosure.\nI:H - Corrupting the mp-\u003eports linked list via stale next pointers after br_multicast_del_pg() enables attacker-influenced kernel heap corruption that can be developed into arbitrary write and privilege escalation.\nA:H - The use-after-free and corrupted multicast database pointers cause kernel oops/panics when subsequent bridge multicast forwarding or MDB operations traverse the broken port-group list, enabling repeatable denial of service."
}
]
}
],
"providerMetadata": {
"dateUpdated": "2026-08-19T16:37:33.031Z",
"orgId": "416baaa9-dc9f-4396-8d5f-8c081fb06d67",
"shortName": "Linux"
},
"references": [
{
"url": "https://git.kernel.org/stable/c/d6c32e2e25a9a06ba021030e26b6d602a277eb72"
},
{
"url": "https://git.kernel.org/stable/c/482bcb85139addb4e8ac8ed10baeda3e0aad4031"
},
{
"url": "https://git.kernel.org/stable/c/1a109cc9890d017c41d77e6c82da739579c49f0b"
},
{
"url": "https://git.kernel.org/stable/c/159ad90cb929c033308bb39a2c5f8fbf393b77aa"
},
{
"url": "https://git.kernel.org/stable/c/4695430e8132420bf8de94da3eb36a6cf35fde6b"
},
{
"url": "https://git.kernel.org/stable/c/0309ebbc570000ea0df11c06b69798e5860c5f6f"
},
{
"url": "https://git.kernel.org/stable/c/4c57056ca6aace2e9f94ae9298bf49ef6b0c95e4"
},
{
"url": "https://git.kernel.org/stable/c/a39789f211b8a4125f0c70e05b30cf715f4f187d"
}
],
"title": "net: bridge: stop fast-leave after deleting a port group",
"x_generator": {
"engine": "bippy-1.2.0"
}
}
},
"cveMetadata": {
"assignerOrgId": "416baaa9-dc9f-4396-8d5f-8c081fb06d67",
"assignerShortName": "Linux",
"cveId": "CVE-2026-74480",
"datePublished": "2026-08-15T12:27:13.803Z",
"dateReserved": "2026-08-15T05:44:03.904Z",
"dateUpdated": "2026-08-19T16:37:33.031Z",
"state": "PUBLISHED"
},
"dataType": "CVE_RECORD",
"dataVersion": "5.2",
"vulnerability-lookup:meta": {
"epss": {
"cve": "CVE-2026-74480",
"date": "2026-09-14",
"epss": "0.0056",
"percentile": "0.44905"
},
"microsoft_vex": {
"current_release_date": "2026-09-11T01:55:22.000Z",
"cve": "CVE-2026-74480",
"id": "msrc_CVE-2026-74480",
"initial_release_date": "2026-08-23T14:59:22.000Z",
"product_status:fixed": "1",
"product_status:known_affected": "1",
"source": "Microsoft CSAF VEX",
"status": "final",
"title": "net: bridge: stop fast-leave after deleting a port group",
"url": "https://msrc.microsoft.com/csaf/vex/2026/msrc_cve-2026-74480.json",
"version": "2"
},
"nvd": "{\"cve\":{\"id\":\"CVE-2026-74480\",\"sourceIdentifier\":\"416baaa9-dc9f-4396-8d5f-8c081fb06d67\",\"published\":\"2026-08-15T13:17:52.820\",\"lastModified\":\"2026-08-19T17:21:05.127\",\"vulnStatus\":\"Received\",\"cveTags\":[],\"descriptions\":[{\"lang\":\"en\",\"value\":\"In the Linux kernel, the following vulnerability has been resolved:\\n\\nnet: bridge: stop fast-leave after deleting a port group\\n\\nbr_multicast_leave_group() iterates mp-\u003eports with pp = \u0026p-\u003enext in\\nits fast-leave path. After br_multicast_del_pg() removes p,\\ncontinuing the loop advances pp through the deleted entry.\\n\\nIf multicast-to-unicast was enabled, the bridge can hold multiple port\\ngroups for the same port and group with different source MAC\\naddresses. Once multicast-to-unicast is disabled,\\nbr_port_group_equal() matches those entries by port only. A fast leave\\ncan then delete one entry and continue from its stale next pointer,\\nleaving mp-\u003eports pointing at a deleted port group.\\n\\nFast leave only needs to remove one matching port group. Break after\\nbr_multicast_del_pg() so the loop stops before dereferencing the\\nremoved entry.\"}],\"affected\":[{\"source\":\"416baaa9-dc9f-4396-8d5f-8c081fb06d67\",\"affectedData\":[{\"vendor\":\"Linux\",\"product\":\"Linux\",\"defaultStatus\":\"unaffected\",\"programFiles\":[\"net/bridge/br_multicast.c\"],\"repo\":\"https://git.kernel.org/pub/scm/linux/kernel/git/stable/linux.git\",\"versions\":[{\"version\":\"6db6f0eae6052b70885562e1733896647ec1d807\",\"lessThan\":\"d6c32e2e25a9a06ba021030e26b6d602a277eb72\",\"versionType\":\"git\",\"status\":\"affected\"},{\"version\":\"6db6f0eae6052b70885562e1733896647ec1d807\",\"lessThan\":\"482bcb85139addb4e8ac8ed10baeda3e0aad4031\",\"versionType\":\"git\",\"status\":\"affected\"},{\"version\":\"6db6f0eae6052b70885562e1733896647ec1d807\",\"lessThan\":\"1a109cc9890d017c41d77e6c82da739579c49f0b\",\"versionType\":\"git\",\"status\":\"affected\"},{\"version\":\"6db6f0eae6052b70885562e1733896647ec1d807\",\"lessThan\":\"159ad90cb929c033308bb39a2c5f8fbf393b77aa\",\"versionType\":\"git\",\"status\":\"affected\"},{\"version\":\"6db6f0eae6052b70885562e1733896647ec1d807\",\"lessThan\":\"4695430e8132420bf8de94da3eb36a6cf35fde6b\",\"versionType\":\"git\",\"status\":\"affected\"},{\"version\":\"6db6f0eae6052b70885562e1733896647ec1d807\",\"lessThan\":\"0309ebbc570000ea0df11c06b69798e5860c5f6f\",\"versionType\":\"git\",\"status\":\"affected\"},{\"version\":\"6db6f0eae6052b70885562e1733896647ec1d807\",\"lessThan\":\"4c57056ca6aace2e9f94ae9298bf49ef6b0c95e4\",\"versionType\":\"git\",\"status\":\"affected\"},{\"version\":\"6db6f0eae6052b70885562e1733896647ec1d807\",\"lessThan\":\"a39789f211b8a4125f0c70e05b30cf715f4f187d\",\"versionType\":\"git\",\"status\":\"affected\"}]},{\"vendor\":\"Linux\",\"product\":\"Linux\",\"defaultStatus\":\"affected\",\"programFiles\":[\"net/bridge/br_multicast.c\"],\"repo\":\"https://git.kernel.org/pub/scm/linux/kernel/git/stable/linux.git\",\"versions\":[{\"version\":\"4.11\",\"status\":\"affected\"},{\"version\":\"0\",\"lessThan\":\"4.11\",\"versionType\":\"semver\",\"status\":\"unaffected\"},{\"version\":\"5.10.265\",\"lessThanOrEqual\":\"5.10.*\",\"versionType\":\"semver\",\"status\":\"unaffected\"},{\"version\":\"5.15.216\",\"lessThanOrEqual\":\"5.15.*\",\"versionType\":\"semver\",\"status\":\"unaffected\"},{\"version\":\"6.1.183\",\"lessThanOrEqual\":\"6.1.*\",\"versionType\":\"semver\",\"status\":\"unaffected\"},{\"version\":\"6.6.151\",\"lessThanOrEqual\":\"6.6.*\",\"versionType\":\"semver\",\"status\":\"unaffected\"},{\"version\":\"6.12.103\",\"lessThanOrEqual\":\"6.12.*\",\"versionType\":\"semver\",\"status\":\"unaffected\"},{\"version\":\"6.18.44\",\"lessThanOrEqual\":\"6.18.*\",\"versionType\":\"semver\",\"status\":\"unaffected\"},{\"version\":\"7.1.8\",\"lessThanOrEqual\":\"7.1.*\",\"versionType\":\"semver\",\"status\":\"unaffected\"},{\"version\":\"7.2\",\"lessThanOrEqual\":\"*\",\"versionType\":\"original_commit_for_fix\",\"status\":\"unaffected\"}]}]}],\"metrics\":{\"cvssMetricV31\":[{\"source\":\"416baaa9-dc9f-4396-8d5f-8c081fb06d67\",\"type\":\"Secondary\",\"cvssData\":{\"version\":\"3.1\",\"vectorString\":\"CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:H/I:H/A:H\",\"baseScore\":9.8,\"baseSeverity\":\"CRITICAL\",\"attackVector\":\"NETWORK\",\"attackComplexity\":\"LOW\",\"privilegesRequired\":\"NONE\",\"userInteraction\":\"NONE\",\"scope\":\"UNCHANGED\",\"confidentialityImpact\":\"HIGH\",\"integrityImpact\":\"HIGH\",\"availabilityImpact\":\"HIGH\"},\"exploitabilityScore\":3.9,\"impactScore\":5.9}]},\"references\":[{\"url\":\"https://git.kernel.org/stable/c/0309ebbc570000ea0df11c06b69798e5860c5f6f\",\"source\":\"416baaa9-dc9f-4396-8d5f-8c081fb06d67\"},{\"url\":\"https://git.kernel.org/stable/c/159ad90cb929c033308bb39a2c5f8fbf393b77aa\",\"source\":\"416baaa9-dc9f-4396-8d5f-8c081fb06d67\"},{\"url\":\"https://git.kernel.org/stable/c/1a109cc9890d017c41d77e6c82da739579c49f0b\",\"source\":\"416baaa9-dc9f-4396-8d5f-8c081fb06d67\"},{\"url\":\"https://git.kernel.org/stable/c/4695430e8132420bf8de94da3eb36a6cf35fde6b\",\"source\":\"416baaa9-dc9f-4396-8d5f-8c081fb06d67\"},{\"url\":\"https://git.kernel.org/stable/c/482bcb85139addb4e8ac8ed10baeda3e0aad4031\",\"source\":\"416baaa9-dc9f-4396-8d5f-8c081fb06d67\"},{\"url\":\"https://git.kernel.org/stable/c/4c57056ca6aace2e9f94ae9298bf49ef6b0c95e4\",\"source\":\"416baaa9-dc9f-4396-8d5f-8c081fb06d67\"},{\"url\":\"https://git.kernel.org/stable/c/a39789f211b8a4125f0c70e05b30cf715f4f187d\",\"source\":\"416baaa9-dc9f-4396-8d5f-8c081fb06d67\"},{\"url\":\"https://git.kernel.org/stable/c/d6c32e2e25a9a06ba021030e26b6d602a277eb72\",\"source\":\"416baaa9-dc9f-4396-8d5f-8c081fb06d67\"}]}}",
"redhat_vex": {
"aggregate_severity": "Important",
"current_release_date": "2026-09-14T11:30:14+00:00",
"cve": "CVE-2026-74480",
"id": "CVE-2026-74480",
"initial_release_date": "2026-08-15T00:00:00+00:00",
"product_status:fixed": "2138",
"product_status:known_affected": "22",
"product_status:known_not_affected": "14",
"source": "Red Hat CSAF VEX",
"status": "final",
"title": "kernel: net: bridge: stop fast-leave after deleting a port group",
"url": "https://security.access.redhat.com/data/csaf/v2/vex/2026/cve-2026-74480.json",
"version": "3"
},
"suse_vex": {
"aggregate_severity": "important",
"current_release_date": "2026-09-12T16:37:54Z",
"cve": "CVE-2026-74480",
"id": "CVE-2026-74480",
"initial_release_date": "2026-08-15T23:52:05Z",
"product_status:known_affected": "344",
"product_status:known_not_affected": "6",
"product_status:recommended": "75",
"source": "SUSE CSAF VEX",
"status": "interim",
"title": "SUSE CVE CVE-2026-74480",
"url": "https://ftp.suse.com/pub/projects/security/csaf-vex/cve-2026-74480.json",
"version": "8"
}
}
}
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Experimental. This forecast is provided for visualization only and may change without notice. Do not use it for operational decisions.
Forecast uses a logistic model when the trend is rising, or an exponential decay model when the trend is falling. Fitted via linearized least squares.
Sightings
| Author | Source | Type | Date | Other |
|---|
Nomenclature
- Seen: The vulnerability was mentioned, discussed, or observed by the user.
- Confirmed: The vulnerability has been validated from an analyst's perspective.
- Published Proof of Concept: A public proof of concept is available for this vulnerability.
- Exploited: The vulnerability was observed as exploited by the user who reported the sighting.
- Patched: The vulnerability was observed as successfully patched by the user who reported the sighting.
- Not exploited: The vulnerability was not observed as exploited by the user who reported the sighting.
- Not confirmed: The user expressed doubt about the validity of the vulnerability.
- Not patched: The vulnerability was not observed as successfully patched by the user who reported the sighting.
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The MITRE ATT&CK techniques below are AI-generated suggestions, inferred from the description of the
vulnerability by the CIRCL/vulnerability-attack-technique-classification-roberta-base
model, served locally by ML-Gateway.
They have not been verified by an analyst and are provided for guidance only.
The approach is described in our paper Mapping CVEs to MITRE ATT&CK Techniques: A Curated Gold-Set Classifier and the Limits of LLM-Assisted Label Expansion.
The approach is described in our paper Mapping CVEs to MITRE ATT&CK Techniques: A Curated Gold-Set Classifier and the Limits of LLM-Assisted Label Expansion.
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