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CVE-2026-63988 (GCVE-0-2026-63988)

Vulnerability from cvelistv5 – Published: 2026-07-19 14:56 – Updated: 2026-07-19 14:56
VLAI
Title
bridge: Fix sleep in atomic context in sysfs path
Summary
In the Linux kernel, the following vulnerability has been resolved: bridge: Fix sleep in atomic context in sysfs path Since the start of the git history, brport_store() always acquired the bridge lock. Back then this decision made sense: The bridge lock protects the STP state of the bridge and its ports and at that time the function was only used by two STP related attributes (cost and priority). Nowadays, brport_store() processes a lot more attributes and most of them do not need the bridge lock: * Bridge flags: Only require RTNL. Read locklessly by the data path. Annotations can be added in net-next. * FDB port flushing: Only requires the FDB lock. * Multicast attributes: Only require the multicast lock. * Group forward mask: Only requires RTNL. Read locklessly by the data path. Annotations can be added in net-next. * Backup port: Only requires RTNL. Read locklessly by the data path. This is a problem as the bridge calls dev_set_promiscuity() when certain bridge port flags change and this function can sleep since the commit cited below, resulting in a splat such as [1]. Fix this by reducing the scope of the bridge lock and only take it when processing the two STP related attributes that require it. Remove the now stale comment from br_switchdev_set_port_flag(). The SWITCHDEV_F_DEFER flag can be removed in net-next. [1] BUG: sleeping function called from invalid context at net/core/dev_addr_lists.c:1262 in_atomic(): 1, irqs_disabled(): 0, non_block: 0, pid: 372, name: bash preempt_count: 201, expected: 0 RCU nest depth: 0, expected: 0 5 locks held by bash/372: #0: ffff88810c51c3f0 (sb_writers#7){.+.+}-{0:0}, at: ksys_write (fs/read_write.c:740) #1: ffff888115ce9480 (&of->mutex){+.+.}-{4:4}, at: kernfs_fop_write_iter (fs/kernfs/file.c:343) #2: ffff88810b9fd330 (kn->active#37){.+.+}-{0:0}, at: kernfs_fop_write_iter (fs/kernfs/file.c:80 fs/kernfs/file.c:344) #3: ffffffffa59473a0 (rtnl_mutex){+.+.}-{4:4}, at: brport_store (net/bridge/br_sysfs_if.c:326) #4: ffff8881099d2d58 (&br->lock){+...}-{3:3}, at: brport_store (./include/linux/spinlock.h:348 net/bridge/br_sysfs_if.c:345) Preemption disabled at: 0x0 Hardware name: Bochs Bochs, BIOS Bochs 01/01/2011 Call Trace: <TASK> dump_stack_lvl (lib/dump_stack.c:94 lib/dump_stack.c:120) __might_resched.cold (kernel/sched/core.c:9163) netif_rx_mode_run (net/core/dev_addr_lists.c:1262) netif_rx_mode_sync (net/core/dev_addr_lists.c:1428) dev_set_promiscuity (net/core/dev_api.c:289) br_manage_promisc (net/bridge/br_if.c:135 net/bridge/br_if.c:172) br_port_flags_change (net/bridge/br_if.c:242 net/bridge/br_if.c:747) store_learning (net/bridge/br_sysfs_if.c:79 net/bridge/br_sysfs_if.c:235) brport_store (net/bridge/br_sysfs_if.c:346) kernfs_fop_write_iter (fs/kernfs/file.c:352) new_sync_write (fs/read_write.c:595) vfs_write (fs/read_write.c:688) ksys_write (fs/read_write.c:740) do_syscall_64 (arch/x86/entry/syscall_64.c:63 arch/x86/entry/syscall_64.c:94) entry_SYSCALL_64_after_hwframe (arch/x86/entry/entry_64.S:121)
Severity
No CVSS data available.
Assigner
References
Impacted products
Vendor Product Version CPE status
Linux Linux Affected: 78cd408356fe3edbac66598772fd347bf3e32c1f , < e976e3f2f2005c6267089a1a3b6344f234a59a55 (git)
Affected: 78cd408356fe3edbac66598772fd347bf3e32c1f , < 2f9cb30d97e45686f3119fff3b30f12259950910 (git)
Affected: 78cd408356fe3edbac66598772fd347bf3e32c1f , < 6d34594cc619d0d4b07d5afcad8b5984f3526dcf (git)
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Linux Linux Affected: 6.15
Unaffected: 0 , < 6.15 (semver)
Unaffected: 6.18.35 , ≤ 6.18.* (semver)
Unaffected: 7.0.12 , ≤ 7.0.* (semver)
Unaffected: 7.1 , ≤ * (original_commit_for_fix)
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{
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          "product": "Linux",
          "programFiles": [
            "net/bridge/br_switchdev.c",
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          "vendor": "Linux",
          "versions": [
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              "version": "6.15"
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                  "vulnerable": true
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              "negate": false,
              "operator": "OR"
            }
          ]
        }
      ],
      "descriptions": [
        {
          "lang": "en",
          "value": "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 (\u0026of-\u003emutex){+.+.}-{4:4}, at: kernfs_fop_write_iter (fs/kernfs/file.c:343)\n#2: ffff88810b9fd330 (kn-\u003eactive#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 (\u0026br-\u003elock){+...}-{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\u003cTASK\u003e\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)"
        }
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      "providerMetadata": {
        "dateUpdated": "2026-07-19T14:56:09.677Z",
        "orgId": "416baaa9-dc9f-4396-8d5f-8c081fb06d67",
        "shortName": "Linux"
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          "url": "https://git.kernel.org/stable/c/e976e3f2f2005c6267089a1a3b6344f234a59a55"
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          "url": "https://git.kernel.org/stable/c/2f9cb30d97e45686f3119fff3b30f12259950910"
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          "url": "https://git.kernel.org/stable/c/6d34594cc619d0d4b07d5afcad8b5984f3526dcf"
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    "assignerShortName": "Linux",
    "cveId": "CVE-2026-63988",
    "datePublished": "2026-07-19T14:56:09.677Z",
    "dateReserved": "2026-07-19T07:54:57.025Z",
    "dateUpdated": "2026-07-19T14:56:09.677Z",
    "state": "PUBLISHED"
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      "date": "2026-09-04",
      "epss": "0.00166",
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    "nvd": "{\"cve\":{\"id\":\"CVE-2026-63988\",\"sourceIdentifier\":\"416baaa9-dc9f-4396-8d5f-8c081fb06d67\",\"published\":\"2026-07-19T16:17:18.060\",\"lastModified\":\"2026-07-30T14:51:11.223\",\"vulnStatus\":\"Awaiting Analysis\",\"cveTags\":[],\"descriptions\":[{\"lang\":\"en\",\"value\":\"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 (\u0026of-\u003emutex){+.+.}-{4:4}, at: kernfs_fop_write_iter (fs/kernfs/file.c:343)\\n#2: ffff88810b9fd330 (kn-\u003eactive#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 (\u0026br-\u003elock){+...}-{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\u003cTASK\u003e\\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)\"}],\"affected\":[{\"source\":\"416baaa9-dc9f-4396-8d5f-8c081fb06d67\",\"affectedData\":[{\"vendor\":\"Linux\",\"product\":\"Linux\",\"defaultStatus\":\"unaffected\",\"programFiles\":[\"net/bridge/br_switchdev.c\",\"net/bridge/br_sysfs_if.c\"],\"repo\":\"https://git.kernel.org/pub/scm/linux/kernel/git/stable/linux.git\",\"versions\":[{\"version\":\"78cd408356fe3edbac66598772fd347bf3e32c1f\",\"lessThan\":\"e976e3f2f2005c6267089a1a3b6344f234a59a55\",\"versionType\":\"git\",\"status\":\"affected\"},{\"version\":\"78cd408356fe3edbac66598772fd347bf3e32c1f\",\"lessThan\":\"2f9cb30d97e45686f3119fff3b30f12259950910\",\"versionType\":\"git\",\"status\":\"affected\"},{\"version\":\"78cd408356fe3edbac66598772fd347bf3e32c1f\",\"lessThan\":\"6d34594cc619d0d4b07d5afcad8b5984f3526dcf\",\"versionType\":\"git\",\"status\":\"affected\"}]},{\"vendor\":\"Linux\",\"product\":\"Linux\",\"defaultStatus\":\"affected\",\"programFiles\":[\"net/bridge/br_switchdev.c\",\"net/bridge/br_sysfs_if.c\"],\"repo\":\"https://git.kernel.org/pub/scm/linux/kernel/git/stable/linux.git\",\"versions\":[{\"version\":\"6.15\",\"status\":\"affected\"},{\"version\":\"0\",\"lessThan\":\"6.15\",\"versionType\":\"semver\",\"status\":\"unaffected\"},{\"version\":\"6.18.35\",\"lessThanOrEqual\":\"6.18.*\",\"versionType\":\"semver\",\"status\":\"unaffected\"},{\"version\":\"7.0.12\",\"lessThanOrEqual\":\"7.0.*\",\"versionType\":\"semver\",\"status\":\"unaffected\"},{\"version\":\"7.1\",\"lessThanOrEqual\":\"*\",\"versionType\":\"original_commit_for_fix\",\"status\":\"unaffected\"}]}]}],\"metrics\":{},\"references\":[{\"url\":\"https://git.kernel.org/stable/c/2f9cb30d97e45686f3119fff3b30f12259950910\",\"source\":\"416baaa9-dc9f-4396-8d5f-8c081fb06d67\"},{\"url\":\"https://git.kernel.org/stable/c/6d34594cc619d0d4b07d5afcad8b5984f3526dcf\",\"source\":\"416baaa9-dc9f-4396-8d5f-8c081fb06d67\"},{\"url\":\"https://git.kernel.org/stable/c/e976e3f2f2005c6267089a1a3b6344f234a59a55\",\"source\":\"416baaa9-dc9f-4396-8d5f-8c081fb06d67\"}]}}",
    "redhat_vex": {
      "aggregate_severity": "Low",
      "current_release_date": "2026-07-21T17:06:03+00:00",
      "cve": "CVE-2026-63988",
      "id": "CVE-2026-63988",
      "initial_release_date": "2026-07-19T00:00:00+00:00",
      "product_status:known_affected": "90",
      "product_status:known_not_affected": "184",
      "source": "Red Hat CSAF VEX",
      "status": "final",
      "title": "kernel: bridge: Fix sleep in atomic context in sysfs path",
      "url": "https://security.access.redhat.com/data/csaf/v2/vex/2026/cve-2026-63988.json",
      "version": "3"
    }
  }
}



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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

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  • Seen: The vulnerability was mentioned, discussed, or observed by the user.
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Detection rules are retrieved from Rulezet.