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vuln-cve/data/2026/80xxx/CVE-2026-80842.json
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{
"dataType": "CVE_RECORD",
"dataVersion": "5.2",
"cveMetadata": {
"cveId": "CVE-2026-80842",
"assignerOrgId": "416baaa9-dc9f-4396-8d5f-8c081fb06d67",
"state": "PUBLISHED",
"assignerShortName": "Linux",
"dateReserved": "2026-08-26T14:34:25.796Z",
"datePublished": "2026-09-04T15:54:52.459Z",
"dateUpdated": "2026-10-19T08:44:35.389Z"
},
"containers": {
"cna": {
"providerMetadata": {
"orgId": "416baaa9-dc9f-4396-8d5f-8c081fb06d67",
"shortName": "Linux",
"dateUpdated": "2026-10-19T08:44:35.389Z"
},
"descriptions": [
{
"lang": "en",
"value": "In the Linux kernel, the following vulnerability has been resolved:\n\nnet: bridge: mcast: fix use-after-free of a master VLAN's multicast context\n\nbr_multicast_toggle_one_vlan() clears BR_VLFLAG_MCAST_ENABLED under\nbr->multicast_lock before stopping a VLAN's multicast context. That is\nthe teardown handshake: lockless readers gate on the flag through\nbr_multicast_ctx_should_use() -> br_multicast_ctx_vlan_disabled(), so\nonce it is cleared under the lock no reader can arm the context again.\n\nFor a master VLAN the handshake never runs. __vlan_del() clears\nBRIDGE_VLAN_INFO_BRENTRY before calling br_vlan_put_master(), so\nbr_multicast_toggle_one_vlan(masterv, false) returns early on\n!br_vlan_is_brentry(vlan): the flag stays set and br->multicast_lock is\nnever taken. br_vlan_put_master() then drains the context in\nbr_multicast_ctx_deinit() and frees the VLAN through call_rcu(), while a\nreader still inside rcu_read_lock() sees the context as enabled and\nre-arms it. The port and port-VLAN branch of the function has no\nbr_vlan_is_brentry() test and flips the flag under br->multicast_lock,\nso it is not affected.\n\nThe reader is the bridge transmit path. For a master VLAN\nbr_multicast_rcv() selects brmctx = &vlan->br_mcast_ctx with\npmctx = NULL, so IGMP sent to the bridge device re-arms the context's\ntimers after br_multicast_ctx_deinit() has already stopped them.\n\n BUG: KASAN: slab-use-after-free in detach_if_pending+0x412/0x4a0\n Write of size 8 at addr ffff88810ac39918 by task brmc/601\n __mod_timer+0x51a/0xc50\n br_multicast_host_join+0x25b/0x390\n __br_multicast_add_group+0x468/0x530\n br_ip4_multicast_add_group+0x1a0/0x260\n br_multicast_rcv+0x2cda/0x61e0\n br_dev_xmit+0x6c4/0x1540\n Allocated by task 610:\n br_vlan_add+0x111/0xb40\n br_vlan_info+0x370/0x3e0\n Freed by task 0:\n kfree+0x1a7/0x4f0\n rcu_core+0x7dc/0x10a0\n\nOnly test br_vlan_is_brentry() when enabling, like the\nbr_multicast_ctx_vlan_global_disabled() test next to it. Disabling then\nalways clears BR_VLFLAG_MCAST_ENABLED under br->multicast_lock before\nbr_multicast_ctx_deinit() drains the context."
}
],
"affected": [
{
"product": "Linux",
"vendor": "Linux",
"defaultStatus": "unaffected",
"repo": "https://git.kernel.org/pub/scm/linux/kernel/git/stable/linux.git",
"programFiles": [
"net/bridge/br_multicast.c"
],
"versions": [
{
"version": "7b54aaaf53cb784411426c64482af0435f7c845e",
"lessThan": "3afaaee2f972aec9059110953adb62fa3cf5c4bd",
"status": "affected",
"versionType": "git"
},
{
"version": "7b54aaaf53cb784411426c64482af0435f7c845e",
"lessThan": "22226a2c3b90f15b0925f1464470d3baa6c5677e",
"status": "affected",
"versionType": "git"
},
{
"version": "7b54aaaf53cb784411426c64482af0435f7c845e",
"lessThan": "7c54fd8cfbcf371a5ef50db5c53fe6e85fb76686",
"status": "affected",
"versionType": "git"
},
{
"version": "7b54aaaf53cb784411426c64482af0435f7c845e",
"lessThan": "3a0ad4fcdfa0b7dba1876de14a12cb65c8b5ca50",
"status": "affected",
"versionType": "git"
},
{
"version": "7b54aaaf53cb784411426c64482af0435f7c845e",
"lessThan": "c069f29da72324697aa4b7cab5b3647a7d24a575",
"status": "affected",
"versionType": "git"
},
{
"version": "7b54aaaf53cb784411426c64482af0435f7c845e",
"lessThan": "3f4752996735e0628af559aa8da1d872c2fac13b",
"status": "affected",
"versionType": "git"
},
{
"version": "7b54aaaf53cb784411426c64482af0435f7c845e",
"lessThan": "57f94d3f4dee8b54d63cefddf1112be4656ef9e6",
"status": "affected",
"versionType": "git"
},
{
"version": "7b54aaaf53cb784411426c64482af0435f7c845e",
"lessThan": "50e5c6605cc9c2dd57bd2d1b3459674d19738983",
"status": "affected",
"versionType": "git"
}
]
},
{
"product": "Linux",
"vendor": "Linux",
"defaultStatus": "affected",
"repo": "https://git.kernel.org/pub/scm/linux/kernel/git/stable/linux.git",
"programFiles": [
"net/bridge/br_multicast.c"
],
"versions": [
{
"version": "5.15",
"status": "affected"
},
{
"version": "0",
"lessThan": "5.15",
"status": "unaffected",
"versionType": "semver"
},
{
"version": "5.15.220",
"lessThanOrEqual": "5.15.*",
"status": "unaffected",
"versionType": "semver"
},
{
"version": "6.1.187",
"lessThanOrEqual": "6.1.*",
"status": "unaffected",
"versionType": "semver"
},
{
"version": "6.6.156",
"lessThanOrEqual": "6.6.*",
"status": "unaffected",
"versionType": "semver"
},
{
"version": "6.12.108",
"lessThanOrEqual": "6.12.*",
"status": "unaffected",
"versionType": "semver"
},
{
"version": "6.18.49",
"lessThanOrEqual": "6.18.*",
"status": "unaffected",
"versionType": "semver"
},
{
"version": "7.1.13",
"lessThanOrEqual": "7.1.*",
"status": "unaffected",
"versionType": "semver"
},
{
"version": "7.2.3",
"lessThanOrEqual": "7.2.*",
"status": "unaffected",
"versionType": "semver"
},
{
"version": "7.3",
"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": "5.15",
"versionEndExcluding": "5.15.220"
},
{
"vulnerable": true,
"criteria": "cpe:2.3:o:linux:linux_kernel:*:*:*:*:*:*:*:*",
"versionStartIncluding": "5.15",
"versionEndExcluding": "6.1.187"
},
{
"vulnerable": true,
"criteria": "cpe:2.3:o:linux:linux_kernel:*:*:*:*:*:*:*:*",
"versionStartIncluding": "5.15",
"versionEndExcluding": "6.6.156"
},
{
"vulnerable": true,
"criteria": "cpe:2.3:o:linux:linux_kernel:*:*:*:*:*:*:*:*",
"versionStartIncluding": "5.15",
"versionEndExcluding": "6.12.108"
},
{
"vulnerable": true,
"criteria": "cpe:2.3:o:linux:linux_kernel:*:*:*:*:*:*:*:*",
"versionStartIncluding": "5.15",
"versionEndExcluding": "6.18.49"
},
{
"vulnerable": true,
"criteria": "cpe:2.3:o:linux:linux_kernel:*:*:*:*:*:*:*:*",
"versionStartIncluding": "5.15",
"versionEndExcluding": "7.1.13"
},
{
"vulnerable": true,
"criteria": "cpe:2.3:o:linux:linux_kernel:*:*:*:*:*:*:*:*",
"versionStartIncluding": "5.15",
"versionEndExcluding": "7.2.3"
},
{
"vulnerable": true,
"criteria": "cpe:2.3:o:linux:linux_kernel:*:*:*:*:*:*:*:*",
"versionStartIncluding": "5.15",
"versionEndExcluding": "7.3"
}
]
}
]
}
],
"references": [
{
"url": "https://git.kernel.org/stable/c/3afaaee2f972aec9059110953adb62fa3cf5c4bd"
},
{
"url": "https://git.kernel.org/stable/c/22226a2c3b90f15b0925f1464470d3baa6c5677e"
},
{
"url": "https://git.kernel.org/stable/c/7c54fd8cfbcf371a5ef50db5c53fe6e85fb76686"
},
{
"url": "https://git.kernel.org/stable/c/3a0ad4fcdfa0b7dba1876de14a12cb65c8b5ca50"
},
{
"url": "https://git.kernel.org/stable/c/c069f29da72324697aa4b7cab5b3647a7d24a575"
},
{
"url": "https://git.kernel.org/stable/c/3f4752996735e0628af559aa8da1d872c2fac13b"
},
{
"url": "https://git.kernel.org/stable/c/57f94d3f4dee8b54d63cefddf1112be4656ef9e6"
},
{
"url": "https://git.kernel.org/stable/c/50e5c6605cc9c2dd57bd2d1b3459674d19738983"
}
],
"title": "net: bridge: mcast: fix use-after-free of a master VLAN's multicast context",
"x_generator": {
"engine": "bippy-1.2.0"
}
}
}
}
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