GHSA-M2V3-P29R-XWMJ
Vulnerability from github – Published: 2026-08-22 18:30 – Updated: 2026-08-25 06:31In the Linux kernel, the following vulnerability has been resolved:
vxlan: do not arm the ageing timer on a device that is down
vxlan_changelink() arms vxlan->age_timer whenever the requested ageing interval differs from the configured one:
if (conf.age_interval != vxlan->cfg.age_interval)
mod_timer(&vxlan->age_timer, jiffies);
There is no netif_running() test, so the timer is armed even on a device that was never brought up. The only synchronous cancel in the driver is the timer_delete_sync() in vxlan_stop(), which is .ndo_stop. netif_close_many() drops devices without IFF_UP before __dev_close_many() runs, so that cancel is skipped for such a device.
vxlan_setup() sets dev->needs_free_netdev = true and age_timer is a member of struct vxlan_dev, so free_netdev() releases the allocation the timer lives in while it is still queued on a timer_base. expire_timers() unlinks the entry before it loads timer->function, so the timer core writes through the freed object's list pointers:
BUG: KASAN: slab-use-after-free in __run_timers+0x208/0x654 Write of size 8 at addr ffff00001adace68 by task true/192 __asan_store8+0x84/0xac __run_timers+0x208/0x654 run_timer_softirq+0x154/0x18c Allocated by task 189: alloc_netdev_mqs+0x64/0x720 rtnl_create_link+0x4ac/0x520 rtnl_newlink+0x758/0xd00 Freed by task 191: netdev_release+0x40/0x58 netdev_run_todo+0x4a4/0x8c0 rtnl_dellink+0x200/0x4e8
The rtnl operations involved are netns-scoped, so an unprivileged user can perform them in a new user and network namespace.
Arming the timer on a down device never had an effect: vxlan_cleanup() returns early on !netif_running(), and vxlan_open() arms the timer for any non-zero interval once the device is brought up. Add the missing test.
Discovered by XBOW, triaged by Baul Lee baul.lee@xbow.com
{
"affected": [],
"aliases": [
"CVE-2026-74615"
],
"database_specific": {
"cwe_ids": [],
"github_reviewed": false,
"github_reviewed_at": null,
"nvd_published_at": "2026-08-22T16:16:34Z",
"severity": "HIGH"
},
"details": "In the Linux kernel, the following vulnerability has been resolved:\n\nvxlan: do not arm the ageing timer on a device that is down\n\nvxlan_changelink() arms vxlan-\u003eage_timer whenever the requested ageing\ninterval differs from the configured one:\n\n\tif (conf.age_interval != vxlan-\u003ecfg.age_interval)\n\t\tmod_timer(\u0026vxlan-\u003eage_timer, jiffies);\n\nThere is no netif_running() test, so the timer is armed even on a device\nthat was never brought up. The only synchronous cancel in the driver is\nthe timer_delete_sync() in vxlan_stop(), which is .ndo_stop.\nnetif_close_many() drops devices without IFF_UP before\n__dev_close_many() runs, so that cancel is skipped for such a device.\n\nvxlan_setup() sets dev-\u003eneeds_free_netdev = true and age_timer is a\nmember of struct vxlan_dev, so free_netdev() releases the allocation the\ntimer lives in while it is still queued on a timer_base.\nexpire_timers() unlinks the entry before it loads timer-\u003efunction, so\nthe timer core writes through the freed object\u0027s list pointers:\n\n BUG: KASAN: slab-use-after-free in __run_timers+0x208/0x654\n Write of size 8 at addr ffff00001adace68 by task true/192\n __asan_store8+0x84/0xac\n __run_timers+0x208/0x654\n run_timer_softirq+0x154/0x18c\n Allocated by task 189:\n alloc_netdev_mqs+0x64/0x720\n rtnl_create_link+0x4ac/0x520\n rtnl_newlink+0x758/0xd00\n Freed by task 191:\n netdev_release+0x40/0x58\n netdev_run_todo+0x4a4/0x8c0\n rtnl_dellink+0x200/0x4e8\n\nThe rtnl operations involved are netns-scoped, so an unprivileged user\ncan perform them in a new user and network namespace.\n\nArming the timer on a down device never had an effect: vxlan_cleanup()\nreturns early on !netif_running(), and vxlan_open() arms the timer for\nany non-zero interval once the device is brought up. Add the missing\ntest.\n\nDiscovered by XBOW, triaged by Baul Lee \u003cbaul.lee@xbow.com\u003e",
"id": "GHSA-m2v3-p29r-xwmj",
"modified": "2026-08-25T06:31:23Z",
"published": "2026-08-22T18:30:26Z",
"references": [
{
"type": "ADVISORY",
"url": "https://nvd.nist.gov/vuln/detail/CVE-2026-74615"
},
{
"type": "WEB",
"url": "https://git.kernel.org/stable/c/26c179d47403d2f919ee914cc02c31d896b59fee"
},
{
"type": "WEB",
"url": "https://git.kernel.org/stable/c/46bb297ad77680e009244f067f27d51cf5b8c7cf"
},
{
"type": "WEB",
"url": "https://git.kernel.org/stable/c/619dd29045e439d0b0f8c6d4fec1af447a050680"
},
{
"type": "WEB",
"url": "https://git.kernel.org/stable/c/6b095e99b9e67ea31f0c4b00260e010898253519"
},
{
"type": "WEB",
"url": "https://git.kernel.org/stable/c/6b4119af544996a545cf84b16f1dbce829ba0de8"
},
{
"type": "WEB",
"url": "https://git.kernel.org/stable/c/9dc561f0522c35bdd66e0646a748814a138ec4ca"
},
{
"type": "WEB",
"url": "https://git.kernel.org/stable/c/b37971686ec59fb027fa4910ba16805e68fddb97"
},
{
"type": "WEB",
"url": "https://git.kernel.org/stable/c/be44d79d14d7f9ae7c8ffb7272142005341b5123"
}
],
"schema_version": "1.4.0",
"severity": [
{
"score": "CVSS:3.1/AV:L/AC:L/PR:L/UI:N/S:C/C:H/I:H/A:H",
"type": "CVSS_V3"
}
]
}
Sightings
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