{
  "affected": [
    {
      "ranges": [
        {
          "events": [
            {
              "introduced": "7b54aaaf53cb784411426c64482af0435f7c845e"
            },
            {
              "fixed": "3afaaee2f972aec9059110953adb62fa3cf5c4bd"
            },
            {
              "fixed": "22226a2c3b90f15b0925f1464470d3baa6c5677e"
            },
            {
              "fixed": "7c54fd8cfbcf371a5ef50db5c53fe6e85fb76686"
            },
            {
              "fixed": "3a0ad4fcdfa0b7dba1876de14a12cb65c8b5ca50"
            },
            {
              "fixed": "c069f29da72324697aa4b7cab5b3647a7d24a575"
            },
            {
              "fixed": "3f4752996735e0628af559aa8da1d872c2fac13b"
            },
            {
              "fixed": "57f94d3f4dee8b54d63cefddf1112be4656ef9e6"
            },
            {
              "fixed": "50e5c6605cc9c2dd57bd2d1b3459674d19738983"
            }
          ],
          "repo": "https://git.kernel.org/pub/scm/linux/kernel/git/stable/linux.git",
          "type": "GIT"
        }
      ]
    },
    {
      "package": {
        "ecosystem": "Linux",
        "name": "Kernel"
      },
      "ranges": [
        {
          "events": [
            {
              "introduced": "5.15.0"
            },
            {
              "fixed": "5.15.220"
            }
          ],
          "type": "ECOSYSTEM"
        },
        {
          "events": [
            {
              "introduced": "5.16.0"
            },
            {
              "fixed": "6.1.187"
            }
          ],
          "type": "ECOSYSTEM"
        },
        {
          "events": [
            {
              "introduced": "6.2.0"
            },
            {
              "fixed": "6.6.156"
            }
          ],
          "type": "ECOSYSTEM"
        },
        {
          "events": [
            {
              "introduced": "6.7.0"
            },
            {
              "fixed": "6.12.108"
            }
          ],
          "type": "ECOSYSTEM"
        },
        {
          "events": [
            {
              "introduced": "6.13.0"
            },
            {
              "fixed": "6.18.49"
            }
          ],
          "type": "ECOSYSTEM"
        },
        {
          "events": [
            {
              "introduced": "6.19.0"
            },
            {
              "fixed": "7.1.13"
            }
          ],
          "type": "ECOSYSTEM"
        },
        {
          "events": [
            {
              "introduced": "7.2.0"
            },
            {
              "fixed": "7.2.3"
            }
          ],
          "type": "ECOSYSTEM"
        }
      ]
    }
  ],
  "database_specific": {
    "cna_assigner": "Linux",
    "osv_generated_from": "https://github.com/CVEProject/cvelistV5/tree/main/cves/2026/80xxx/CVE-2026-80842.json"
  },
  "details": "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-\u003emulticast_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() -\u003e 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-\u003emulticast_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-\u003emulticast_lock,\nso it is not affected.\n\nThe reader is the bridge transmit path.  For a master VLAN\nbr_multicast_rcv() selects brmctx = \u0026vlan-\u003ebr_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-\u003emulticast_lock before\nbr_multicast_ctx_deinit() drains the context.",
  "id": "CVE-2026-80842",
  "modified": "2026-09-06T03:30:31.095708395Z",
  "published": "2026-09-04T15:54:52.459Z",
  "references": [
    {
      "type": "WEB",
      "url": "https://git.kernel.org/stable/c/22226a2c3b90f15b0925f1464470d3baa6c5677e"
    },
    {
      "type": "WEB",
      "url": "https://git.kernel.org/stable/c/3a0ad4fcdfa0b7dba1876de14a12cb65c8b5ca50"
    },
    {
      "type": "WEB",
      "url": "https://git.kernel.org/stable/c/3afaaee2f972aec9059110953adb62fa3cf5c4bd"
    },
    {
      "type": "WEB",
      "url": "https://git.kernel.org/stable/c/3f4752996735e0628af559aa8da1d872c2fac13b"
    },
    {
      "type": "WEB",
      "url": "https://git.kernel.org/stable/c/50e5c6605cc9c2dd57bd2d1b3459674d19738983"
    },
    {
      "type": "WEB",
      "url": "https://git.kernel.org/stable/c/57f94d3f4dee8b54d63cefddf1112be4656ef9e6"
    },
    {
      "type": "WEB",
      "url": "https://git.kernel.org/stable/c/7c54fd8cfbcf371a5ef50db5c53fe6e85fb76686"
    },
    {
      "type": "WEB",
      "url": "https://git.kernel.org/stable/c/c069f29da72324697aa4b7cab5b3647a7d24a575"
    },
    {
      "type": "ADVISORY",
      "url": "https://github.com/CVEProject/cvelistV5/tree/main/cves/2026/80xxx/CVE-2026-80842.json"
    },
    {
      "type": "ADVISORY",
      "url": "https://nvd.nist.gov/vuln/detail/CVE-2026-80842"
    },
    {
      "type": "PACKAGE",
      "url": "https://git.kernel.org/pub/scm/linux/kernel/git/stable/linux.git"
    }
  ],
  "schema_version": "1.9.0",
  "summary": "net: bridge: mcast: fix use-after-free of a master VLAN's multicast context"
}