GHSA-4746-9QHC-MC6F
Vulnerability from github – Published: 2026-09-25 12:31 – Updated: 2026-10-21 15:41In the Linux kernel, the following vulnerability has been resolved:
bpf: Preserve inner map identity in callback frames
Callback frame constructors initialize map-typed argument registers with __mark_reg_known_zero() and then restore map_ptr. This clears map_uid, which is the only field distinguishing inner maps that share an inner_map_meta template.
When a timer callback invokes bpf_for_each_map_elem() on a second inner map, both the saved first map and the second map value can reach the nested callback as the same template with map_uid zero. bpf_timer_init() then accepts pairing the timer from the second map with the first map.
The runtime records the first map in the timer without taking a reference. Freeing that map does not find the timer stored in the second map, so a later timer callback dereferences the freed map.
Copy map_uid from the same caller register as map_ptr when constructing for-each, timer/workqueue, and task-work callback arguments. The existing identity check can then reject mismatched inner maps while allowing a callback value to be paired with its actual map.
{
"affected": [],
"aliases": [
"CVE-2026-98033"
],
"database_specific": {
"cwe_ids": [],
"github_reviewed": false,
"github_reviewed_at": null,
"nvd_published_at": "2026-09-25T11:17:32Z",
"severity": null
},
"details": "In the Linux kernel, the following vulnerability has been resolved:\n\nbpf: Preserve inner map identity in callback frames\n\nCallback frame constructors initialize map-typed argument registers with\n__mark_reg_known_zero() and then restore map_ptr. This clears map_uid,\nwhich is the only field distinguishing inner maps that share an\ninner_map_meta template.\n\nWhen a timer callback invokes bpf_for_each_map_elem() on a second inner\nmap, both the saved first map and the second map value can reach the nested\ncallback as the same template with map_uid zero. bpf_timer_init() then\naccepts pairing the timer from the second map with the first map.\n\nThe runtime records the first map in the timer without taking a reference.\nFreeing that map does not find the timer stored in the second map, so a\nlater timer callback dereferences the freed map.\n\nCopy map_uid from the same caller register as map_ptr when constructing\nfor-each, timer/workqueue, and task-work callback arguments. The existing\nidentity check can then reject mismatched inner maps while allowing a\ncallback value to be paired with its actual map.",
"id": "GHSA-4746-9qhc-mc6f",
"modified": "2026-10-21T15:41:39Z",
"published": "2026-09-25T12:31:33Z",
"references": [
{
"type": "ADVISORY",
"url": "https://nvd.nist.gov/vuln/detail/CVE-2026-98033"
},
{
"type": "WEB",
"url": "https://git.kernel.org/stable/c/08b534bafdd9de65b6374474a8fe719c90eb3b01"
},
{
"type": "WEB",
"url": "https://git.kernel.org/stable/c/166221c52d3ca332f8699a854efca8e2704bb137"
},
{
"type": "WEB",
"url": "https://git.kernel.org/stable/c/66ff2eff093d2a0838f39c713eeb590bc0946c2a"
},
{
"type": "WEB",
"url": "https://git.kernel.org/stable/c/b90c5d770dad910fb89e6c1b15052a8a1e8db752"
},
{
"type": "WEB",
"url": "https://git.kernel.org/stable/c/cf85e4f94d7feef8b3c4c90dbe2468595a48393b"
}
],
"schema_version": "1.4.0",
"severity": []
}
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