CVE-2026-63988: Software Security Vulnerability Vulnerability

{
  "schema_version" : "1.4.0",
  "id" : "GHSA-qqj9-pc4p-85gc",
  "modified" : "2026-10-08T15:32:31Z",
  "published" : "2026-07-19T18:31:48Z",
  "aliases" : [ "CVE-2026-63988" ],
  "details" : "In the Linux kernel, the following vulnerability has been resolved:\n\nbridge: Fix sleep in atomic context in sysfs path\n\nSince the start of the git history, brport_store() always acquired the\nbridge lock. Back then this decision made sense: The bridge lock\nprotects the STP state of the bridge and its ports and at that time the\nfunction was only used by two STP related attributes (cost and\npriority).\n\nNowadays, brport_store() processes a lot more attributes and most of\nthem do not need the bridge lock:\n\n* Bridge flags: Only require RTNL. Read locklessly by the data path.\n  Annotations can be added in net-next.\n\n* FDB port flushing: Only requires the FDB lock.\n\n* Multicast attributes: Only require the multicast lock.\n\n* Group forward mask: Only requires RTNL. Read locklessly by the data\n  path. Annotations can be added in net-next.\n\n* Backup port: Only requires RTNL. Read locklessly by the data path.\n\nThis is a problem as the bridge calls dev_set_promiscuity() when certain\nbridge port flags change and this function can sleep since the commit\ncited below, resulting in a splat such as [1].\n\nFix this by reducing the scope of the bridge lock and only take it when\nprocessing the two STP related attributes that require it. Remove the\nnow stale comment from br_switchdev_set_port_flag(). The\nSWITCHDEV_F_DEFER flag can be removed in net-next.\n\n[1]\nBUG: sleeping function called from invalid context at net/core/dev_addr_lists.c:1262\nin_atomic(): 1, irqs_disabled(): 0, non_block: 0, pid: 372, name: bash\npreempt_count: 201, expected: 0\nRCU nest depth: 0, expected: 0\n5 locks held by bash/372:\n#0: ffff88810c51c3f0 (sb_writers#7){.+.+}-{0:0}, at: ksys_write (fs/read_write.c:740)\n#1: ffff888115ce9480 (&of->mutex){+.+.}-{4:4}, at: kernfs_fop_write_iter (fs/kernfs/file.c:343)\n#2: ffff88810b9fd330 (kn->active#37){.+.+}-{0:0}, at: kernfs_fop_write_iter (fs/kernfs/file.c:80 fs/kernfs/file.c:344)\n#3: ffffffffa59473a0 (rtnl_mutex){+.+.}-{4:4}, at: brport_store (net/bridge/br_sysfs_if.c:326)\n#4: ffff8881099d2d58 (&br->lock){+...}-{3:3}, at: brport_store (./include/linux/spinlock.h:348 net/bridge/br_sysfs_if.c:345)\nPreemption disabled at:\n 0x0\nHardware name: Bochs Bochs, BIOS Bochs 01/01/2011\nCall Trace:\n<TASK>\ndump_stack_lvl (lib/dump_stack.c:94 lib/dump_stack.c:120)\n__might_resched.cold (kernel/sched/core.c:9163)\nnetif_rx_mode_run (net/core/dev_addr_lists.c:1262)\nnetif_rx_mode_sync (net/core/dev_addr_lists.c:1428)\ndev_set_promiscuity (net/core/dev_api.c:289)\nbr_manage_promisc (net/bridge/br_if.c:135 net/bridge/br_if.c:172)\nbr_port_flags_change (net/bridge/br_if.c:242 net/bridge/br_if.c:747)\nstore_learning (net/bridge/br_sysfs_if.c:79 net/bridge/br_sysfs_if.c:235)\nbrport_store (net/bridge/br_sysfs_if.c:346)\nkernfs_fop_write_iter (fs/kernfs/file.c:352)\nnew_sync_write (fs/read_write.c:595)\nvfs_write (fs/read_write.c:688)\nksys_write (fs/read_write.c:740)\ndo_syscall_64 (arch/x86/entry/syscall_64.c:63 arch/x86/entry/syscall_64.c:94)\nentry_SYSCALL_64_after_hwframe (arch/x86/entry/entry_64.S:121)",
  "severity" : [ {
    "type" : "CVSS_V3",
    "score" : "CVSS:3.1/AV:L/AC:L/PR:L/UI:N/S:U/C:N/I:N/A:H"
  } ],
  "affected" : [ ],
  "references" : [ {
    "type" : "ADVISORY",
    "url" : "https://nvd.nist.gov/vuln/detail/CVE-2026-63988"
  }, {
    "type" : "WEB",
    "url" : "https://git.kernel.org/stable/c/2f9cb30d97e45686f3119fff3b30f12259950910"
  }, {
    "type" : "WEB",
    "url" : "https://git.kernel.org/stable/c/6d34594cc619d0d4b07d5afcad8b5984f3526dcf"
  }, {
    "type" : "WEB",
    "url" : "https://git.kernel.org/stable/c/e976e3f2f2005c6267089a1a3b6344f234a59a55"
  } ],
  "database_specific" : {
    "cwe_ids" : [ "CWE-667" ],
    "severity" : "MODERATE",
    "github_reviewed" : false,
    "github_reviewed_at" : null,
    "nvd_published_at" : "2026-07-19T16:17:18Z"
  }
}