GHSA-F4J9-RGF4-2RMJ
Vulnerability from github – Published: 2026-08-22 18:30 – Updated: 2026-08-27 15:31In the Linux kernel, the following vulnerability has been resolved:
perf/core: Fix group leader use-after-free after sibling detach
perf_group_detach() handles leader and sibling detach differently. When the group leader is detached, all siblings are promoted to singleton events and their group_leader pointer is reset to themselves. When a sibling is detached, it is removed from the leader's sibling_list, but its group_leader pointer is left pointing at the old leader.
That is harmless when the sibling is being closed and freed immediately, as in the DETACH_DEAD path. It is not safe when the sibling is detached but kept alive, such as during CPU hotplug with DETACH_GROUP. In that case the sibling is removed from the context, while its file descriptor can still keep it alive.
A typical failing sequence is:
- A group contains leader L and sibling S.
- CPU hot-unplug detaches S with DETACH_GROUP, removing it from L->sibling_list but leaving S->group_leader == L.
- L is later closed and freed.
- A PERF_IOC_FLAG_GROUP ioctl on S follows S->group_leader and dereferences the freed leader.
This was reproduced by running the perf event fuzzer, CPU hotplug, and a stress workload concurrently:
Unable to handle kernel paging request at virtual address 006b6b6b6b6b6cdb CPU: 2 PID: 12489 Comm: perf_fuzzer 6.18.7 PREEMPT pc : perf_ioctl+0x34c/0xc68 x20: ffffff89a3fa2c70 x8 : 6b6b6b6b6b6b6b6b Code: 943c4a0e 340047a0 f9404a94 f9411e88 (f940b908) Call trace: perf_ioctl+0x34c/0xc68 (P) __arm64_sys_ioctl+0xa0/0xf4 invoke_syscall+0x58/0xe4 el0_svc_common+0xa8/0xdc do_el0_svc+0x1c/0x28 el0_svc+0x40/0xc0 el0t_64_sync_handler+0x68/0xdc el0t_64_sync+0x1c4/0x1c8
The fault happened in perf_ioctl(), where perf_event_for_each() follows the stale group_leader pointer and perf_event_for_each_child() then dereferences the freed leader's context.
Fix the use-after-free by promoting the detached sibling to a singleton. Also fix __event_disable() cgroup accounting and event state change.
{
"affected": [],
"aliases": [
"CVE-2026-74637"
],
"database_specific": {
"cwe_ids": [],
"github_reviewed": false,
"github_reviewed_at": null,
"nvd_published_at": "2026-08-22T16:16:36Z",
"severity": "HIGH"
},
"details": "In the Linux kernel, the following vulnerability has been resolved:\n\nperf/core: Fix group leader use-after-free after sibling detach\n\nperf_group_detach() handles leader and sibling detach differently. When the\ngroup leader is detached, all siblings are promoted to singleton events and\ntheir group_leader pointer is reset to themselves. When a sibling is\ndetached, it is removed from the leader\u0027s sibling_list, but its\ngroup_leader pointer is left pointing at the old leader.\n\nThat is harmless when the sibling is being closed and freed immediately, as\nin the DETACH_DEAD path. It is not safe when the sibling is detached but\nkept alive, such as during CPU hotplug with DETACH_GROUP. In that case the\nsibling is removed from the context, while its file descriptor can still\nkeep it alive.\n\nA typical failing sequence is:\n\n - A group contains leader L and sibling S.\n - CPU hot-unplug detaches S with DETACH_GROUP, removing it from\n L-\u003esibling_list but leaving S-\u003egroup_leader == L.\n - L is later closed and freed.\n - A PERF_IOC_FLAG_GROUP ioctl on S follows S-\u003egroup_leader and\n dereferences the freed leader.\n\nThis was reproduced by running the perf event fuzzer, CPU hotplug, and a\nstress workload concurrently:\n\n Unable to handle kernel paging request at virtual address 006b6b6b6b6b6cdb\n CPU: 2 PID: 12489 Comm: perf_fuzzer 6.18.7 PREEMPT\n pc : perf_ioctl+0x34c/0xc68\n x20: ffffff89a3fa2c70 x8 : 6b6b6b6b6b6b6b6b\n Code: 943c4a0e 340047a0 f9404a94 f9411e88 (f940b908)\n Call trace:\n perf_ioctl+0x34c/0xc68 (P)\n __arm64_sys_ioctl+0xa0/0xf4\n invoke_syscall+0x58/0xe4\n el0_svc_common+0xa8/0xdc\n do_el0_svc+0x1c/0x28\n el0_svc+0x40/0xc0\n el0t_64_sync_handler+0x68/0xdc\n el0t_64_sync+0x1c4/0x1c8\n\nThe fault happened in perf_ioctl(), where perf_event_for_each() follows\nthe stale group_leader pointer and perf_event_for_each_child() then\ndereferences the freed leader\u0027s context.\n\nFix the use-after-free by promoting the detached sibling to a singleton.\nAlso fix __event_disable() cgroup accounting and event state change.",
"id": "GHSA-f4j9-rgf4-2rmj",
"modified": "2026-08-27T15:31:30Z",
"published": "2026-08-22T18:30:27Z",
"references": [
{
"type": "ADVISORY",
"url": "https://nvd.nist.gov/vuln/detail/CVE-2026-74637"
},
{
"type": "WEB",
"url": "https://git.kernel.org/stable/c/1e7abfeb23c12bf46f6457e4a3e1a1a300d50619"
},
{
"type": "WEB",
"url": "https://git.kernel.org/stable/c/42c5ca1f0a288a52878bd72a5595b08261057438"
},
{
"type": "WEB",
"url": "https://git.kernel.org/stable/c/80c6054a4c40a0ffad82acef9f9a0dee108d152a"
},
{
"type": "WEB",
"url": "https://git.kernel.org/stable/c/8e92e03984364d93e0d5b0acd81c95eca773f034"
},
{
"type": "WEB",
"url": "https://git.kernel.org/stable/c/8f867c0e8da4c2303d91adf45acb6b1820966c27"
},
{
"type": "WEB",
"url": "https://git.kernel.org/stable/c/a979a642402d0b1f856c7a729b4cb2d92de4cf2f"
},
{
"type": "WEB",
"url": "https://git.kernel.org/stable/c/b42948f9e0d1ea4dbd5742ce1dfc7688de5d4a35"
},
{
"type": "WEB",
"url": "https://git.kernel.org/stable/c/f8a07021679aadfb6d63b209207ccc41f26982d1"
}
],
"schema_version": "1.4.0",
"severity": [
{
"score": "CVSS:3.1/AV:L/AC:L/PR:L/UI:N/S:U/C:H/I:H/A:H",
"type": "CVSS_V3"
}
]
}
Sightings
| Author | Source | Type | Date | Other |
|---|
Nomenclature
- Seen: The vulnerability was mentioned, discussed, or observed by the user.
- Confirmed: The vulnerability has been validated from an analyst's perspective.
- Published Proof of Concept: A public proof of concept is available for this vulnerability.
- Exploited: The vulnerability was observed as exploited by the user who reported the sighting.
- Patched: The vulnerability was observed as successfully patched by the user who reported the sighting.
- Not exploited: The vulnerability was not observed as exploited by the user who reported the sighting.
- Not confirmed: The user expressed doubt about the validity of the vulnerability.
- Not patched: The vulnerability was not observed as successfully patched by the user who reported the sighting.
The approach is described in our paper Mapping CVEs to MITRE ATT&CK Techniques: A Curated Gold-Set Classifier and the Limits of LLM-Assisted Label Expansion.