CVE-2026-64525
In the Linux kernel, the following vulnerability has been resolved:
xfrm: move policy_bydst RCU sync from per-netns .exit to .pre_exit
The struct pernet_operations docstring in include/net/net_namespace.h explicitly warns against blocking RCU primitives in .exit handlers:
xfrm_policy_fini() violates this: it calls synchronize_rcu() before freeing the policy_bydst hash tables (so no RCU reader is mid- traversal at free time), but runs from xfrm_net_ops.exit -- once per namespace -- so a cleanup_net() of N namespaces pays N full RCU grace periods serially.
Use the documented pre_exit/exit split. Move the policy flush (and the workqueue drains it depends on) into a new .pre_exit handler; xfrm_policy_fini() then runs in .exit and frees the hash tables after the synchronize_rcu_expedited() that cleanup_net() guarantees between the two phases. Providing O(1) RCU grace periods per batch instead of O(N).
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Observed on Linux 6.18 with a workload doing unshare(CLONE_NEWNET) at ~13/sec sustained: cleanup_net() and the netns_wq rescuer kthread both stuck in xfrm_policy_fini()'s synchronize_rcu(), >300k struct net accumulated in the cleanup queue, Percpu in /proc/meminfo climbed to 130+ GB on 256-CPU hosts, and memcg OOMs followed. setup_net and __put_net counts were balanced, ruling out a refcount leak.
Detalles técnicos trazas, registros y código del informe original
Exit methods using blocking RCU primitives, such as
synchronize_rcu(), should be implemented via exit_batch.
[...]
Please, avoid synchronize_rcu() at all, where it's possible.
Note that a combination of pre_exit() and exit() can
be used, since a synchronize_rcu() is guaranteed between
the calls.CVSS
NVD no ha asignado puntuación CVSS a esta CVE (habitual desde el cambio de política de abril de 2026).
Probabilidad de explotación (EPSS)
- Probabilidad de explotación en los próximos 30 días: 0.21%
- Percentil entre todas las CVEs puntuadas: 10
- Fecha de la puntuación: 6/10/2026
EPSS (Exploit Prediction Scoring System, de FIRST) estima la probabilidad de que una vulnerabilidad sea explotada en 30 días. Complementa a CVSS (impacto) y a CISA KEV (explotación confirmada).
Tecnologías afectadas (1)
⚠ Inferidas por IA a partir de la descripción — NVD aún no ha analizado esta CVE; no son CPE verificados.
Referencias
JSON original (NVD)
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{
"id": "CVE-2026-64525",
"cveTags": [],
"metrics": {},
"affected": [
{
"source": "416baaa9-dc9f-4396-8d5f-8c081fb06d67",
"affectedData": [
{
"repo": "https://git.kernel.org/pub/scm/linux/kernel/git/stable/linux.git",
"vendor": "Linux",
"product": "Linux",
"versions": [
{
"status": "affected",
"version": "438b1f668ad58f46ce699bb48e4698a7839e3f9e",
"lessThan": "bca6386dc08750fc7cdcbc7683473748ba3114b9",
"versionType": "git"
},
{
"status": "affected",
"version": "3733fce2871c9bca9dd18a1a23b1432ea215a094",
"lessThan": "91cc13978ab0bc6f669139f53e7e613a860d10e0",
"versionType": "git"
},
{
"status": "affected",
"version": "069daad4f2ae9c5c108131995529d5f02392c446",
"lessThan": "d14ae8ef88c2c6590e107db61b6adce148cec7b3",
"versionType": "git"
},
{
"status": "affected",
"version": "069daad4f2ae9c5c108131995529d5f02392c446",
"lessThan": "3e52417318473782012b236d0325bf7d2266a597",
"versionType": "git"
},
{
"status": "affected",
"version": "b66920a3348c0f63ba18365248fa21fbf0b3a937",
"versionType": "git"
},
{
"status": "affected",
"version": "33a3149dd81a1e2f52b80ee1e0fc380b39f3d028",
"versionType": "git"
},
{
"status": "affected",
"version": "6.12.83",
"lessThan": "6.12.93",
"versionType": "semver"
},
{
"status": "affected",
"version": "6.18.24",
"lessThan": "6.18.35",
"versionType": "semver"
},
{
"status": "affected",
"version": "6.6.136",
"lessThan": "6.7",
"versionType": "semver"
},
{
"status": "affected",
"version": "6.19.14",
"lessThan": "6.20",
"versionType": "semver"
}
],
"programFiles": [
"net/xfrm/xfrm_policy.c"
],
"defaultStatus": "unaffected"
},
{
"repo": "https://git.kernel.org/pub/scm/linux/kernel/git/stable/linux.git",
"vendor": "Linux",
"product": "Linux",
"versions": [
{
"status": "affected",
"version": "7.0"
},
{
"status": "unaffected",
"version": "0",
"lessThan": "7.0",
"versionType": "semver"
},
{
"status": "unaffected",
"version": "6.12.93",
"versionType": "semver",
"lessThanOrEqual": "6.12.*"
},
{
"status": "unaffected",
"version": "6.18.35",
"versionType": "semver",
"lessThanOrEqual": "6.18.*"
},
{
"status": "unaffected",
"version": "7.0.12",
"versionType": "semver",
"lessThanOrEqual": "7.0.*"
},
{
"status": "unaffected",
"version": "7.1",
"versionType": "original_commit_for_fix",
"lessThanOrEqual": "*"
}
],
"programFiles": [
"net/xfrm/xfrm_policy.c"
],
"defaultStatus": "affected"
}
]
}
],
"published": "2026-07-25T10:17:38.830",
"references": [
{
"url": "https://git.kernel.org/stable/c/3e52417318473782012b236d0325bf7d2266a597",
"source": "416baaa9-dc9f-4396-8d5f-8c081fb06d67"
},
{
"url": "https://git.kernel.org/stable/c/91cc13978ab0bc6f669139f53e7e613a860d10e0",
"source": "416baaa9-dc9f-4396-8d5f-8c081fb06d67"
},
{
"url": "https://git.kernel.org/stable/c/bca6386dc08750fc7cdcbc7683473748ba3114b9",
"source": "416baaa9-dc9f-4396-8d5f-8c081fb06d67"
},
{
"url": "https://git.kernel.org/stable/c/d14ae8ef88c2c6590e107db61b6adce148cec7b3",
"source": "416baaa9-dc9f-4396-8d5f-8c081fb06d67"
}
],
"vulnStatus": "Received",
"descriptions": [
{
"lang": "en",
"value": "In the Linux kernel, the following vulnerability has been resolved:\n\nxfrm: move policy_bydst RCU sync from per-netns .exit to .pre_exit\n\nThe struct pernet_operations docstring in include/net/net_namespace.h\nexplicitly warns against blocking RCU primitives in .exit handlers:\n\n Exit methods using blocking RCU primitives, such as\n synchronize_rcu(), should be implemented via exit_batch.\n [...]\n Please, avoid synchronize_rcu() at all, where it's possible.\n\n Note that a combination of pre_exit() and exit() can\n be used, since a synchronize_rcu() is guaranteed between\n the calls.\n\nxfrm_policy_fini() violates this: it calls synchronize_rcu() before\nfreeing the policy_bydst hash tables (so no RCU reader is mid-\ntraversal at free time), but runs from xfrm_net_ops.exit -- once per\nnamespace -- so a cleanup_net() of N namespaces pays N full RCU\ngrace periods serially.\n\nUse the documented pre_exit/exit split. Move the policy flush (and\nthe workqueue drains it depends on) into a new .pre_exit handler;\nxfrm_policy_fini() then runs in .exit and frees the hash tables\nafter the synchronize_rcu_expedited() that cleanup_net() guarantees\nbetween the two phases. Providing O(1) RCU grace periods per batch\ninstead of O(N).\n\nObserved on Linux 6.18 with a workload doing unshare(CLONE_NEWNET)\nat ~13/sec sustained: cleanup_net() and the netns_wq rescuer kthread\nboth stuck in xfrm_policy_fini()'s synchronize_rcu(), >300k struct\nnet accumulated in the cleanup queue, Percpu in /proc/meminfo climbed\nto 130+ GB on 256-CPU hosts, and memcg OOMs followed. setup_net and\n__put_net counts were balanced, ruling out a refcount leak."
}
],
"lastModified": "2026-07-25T10:17:38.830",
"sourceIdentifier": "416baaa9-dc9f-4396-8d5f-8c081fb06d67"
}