Vulnerability-Lookup

CVE-2026-64525 (GCVE-0-2026-64525)

Vulnerability from cvelistv5 – Published: 2026-07-25 09:20 – Updated: 2026-07-25 09:20

Title

xfrm: move policy_bydst RCU sync from per-netns .exit to .pre_exit

Summary

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: 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. 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). 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.

Severity

No CVSS data available.

Assigner

Linux

References

4 references

URL	Tags
https://git.kernel.org/stable/c/bca6386dc08750fc7…
https://git.kernel.org/stable/c/91cc13978ab0bc6f6…
https://git.kernel.org/stable/c/d14ae8ef88c2c6590…
https://git.kernel.org/stable/c/3e524173184737820…

Impacted products

2 products

Vendor	Product	Version
Linux	Linux	Affected: 438b1f668ad58f46ce699bb48e4698a7839e3f9e , < bca6386dc08750fc7cdcbc7683473748ba3114b9 (git) Affected: 3733fce2871c9bca9dd18a1a23b1432ea215a094 , < 91cc13978ab0bc6f669139f53e7e613a860d10e0 (git) Affected: 069daad4f2ae9c5c108131995529d5f02392c446 , < d14ae8ef88c2c6590e107db61b6adce148cec7b3 (git) Affected: 069daad4f2ae9c5c108131995529d5f02392c446 , < 3e52417318473782012b236d0325bf7d2266a597 (git) Affected: b66920a3348c0f63ba18365248fa21fbf0b3a937 (git) Affected: 33a3149dd81a1e2f52b80ee1e0fc380b39f3d028 (git) Affected: 6.12.83 , < 6.12.93 (semver) Affected: 6.18.24 , < 6.18.35 (semver) Affected: 6.6.136 , < 6.7 (semver) Affected: 6.19.14 , < 6.20 (semver)
Linux	Linux	Affected: 7.0 Unaffected: 0 , < 7.0 (semver) Unaffected: 6.12.93 , ≤ 6.12.* (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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      "cpeApplicability": [
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          "nodes": [
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        }
      ],
      "providerMetadata": {
        "dateUpdated": "2026-07-25T09:20:49.256Z",
        "orgId": "416baaa9-dc9f-4396-8d5f-8c081fb06d67",
        "shortName": "Linux"
      },
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        },
        {
          "url": "https://git.kernel.org/stable/c/3e52417318473782012b236d0325bf7d2266a597"
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      "title": "xfrm: move policy_bydst RCU sync from per-netns .exit to .pre_exit",
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    "cveId": "CVE-2026-64525",
    "datePublished": "2026-07-25T09:20:49.256Z",
    "dateReserved": "2026-07-19T15:36:31.794Z",
    "dateUpdated": "2026-07-25T09:20:49.256Z",
    "state": "PUBLISHED"
  },
  "dataType": "CVE_RECORD",
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  "vulnerability-lookup:meta": {
    "epss": {
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      "date": "2026-07-25",
      "epss": "0.00209",
      "percentile": "0.11176"
    },
    "nvd": "{\"cve\":{\"id\":\"CVE-2026-64525\",\"sourceIdentifier\":\"416baaa9-dc9f-4396-8d5f-8c081fb06d67\",\"published\":\"2026-07-25T10:17:38.830\",\"lastModified\":\"2026-07-25T10:17:38.830\",\"vulnStatus\":\"Received\",\"cveTags\":[],\"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\u0027s 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()\u0027s synchronize_rcu(), \u003e300k 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.\"}],\"affected\":[{\"source\":\"416baaa9-dc9f-4396-8d5f-8c081fb06d67\",\"affectedData\":[{\"vendor\":\"Linux\",\"product\":\"Linux\",\"defaultStatus\":\"unaffected\",\"programFiles\":[\"net/xfrm/xfrm_policy.c\"],\"repo\":\"https://git.kernel.org/pub/scm/linux/kernel/git/stable/linux.git\",\"versions\":[{\"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\",\"status\":\"affected\"}]},{\"vendor\":\"Linux\",\"product\":\"Linux\",\"defaultStatus\":\"affected\",\"programFiles\":[\"net/xfrm/xfrm_policy.c\"],\"repo\":\"https://git.kernel.org/pub/scm/linux/kernel/git/stable/linux.git\",\"versions\":[{\"version\":\"7.0\",\"status\":\"affected\"},{\"version\":\"0\",\"lessThan\":\"7.0\",\"versionType\":\"semver\",\"status\":\"unaffected\"},{\"version\":\"6.12.93\",\"lessThanOrEqual\":\"6.12.*\",\"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/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\"}]}}"
  }
}

GHSA-PHMC-55J6-972R

Vulnerability from github – Published: 2026-07-25 12:31 – Updated: 2026-07-25 12:31

Details

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:

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.

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).

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.

Show details on source website

JSON

To clipboard

{
  "affected": [],
  "aliases": [
    "CVE-2026-64525"
  ],
  "database_specific": {
    "cwe_ids": [],
    "github_reviewed": false,
    "github_reviewed_at": null,
    "nvd_published_at": "2026-07-25T10:17:38Z",
    "severity": null
  },
  "details": "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\u0027s 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()\u0027s synchronize_rcu(), \u003e300k 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.",
  "id": "GHSA-phmc-55j6-972r",
  "modified": "2026-07-25T12:31:39Z",
  "published": "2026-07-25T12:31:39Z",
  "references": [
    {
      "type": "ADVISORY",
      "url": "https://nvd.nist.gov/vuln/detail/CVE-2026-64525"
    },
    {
      "type": "WEB",
      "url": "https://git.kernel.org/stable/c/3e52417318473782012b236d0325bf7d2266a597"
    },
    {
      "type": "WEB",
      "url": "https://git.kernel.org/stable/c/91cc13978ab0bc6f669139f53e7e613a860d10e0"
    },
    {
      "type": "WEB",
      "url": "https://git.kernel.org/stable/c/bca6386dc08750fc7cdcbc7683473748ba3114b9"
    },
    {
      "type": "WEB",
      "url": "https://git.kernel.org/stable/c/d14ae8ef88c2c6590e107db61b6adce148cec7b3"
    }
  ],
  "schema_version": "1.4.0",
  "severity": []
}

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.

Detection rules are retrieved from Rulezet.

The MITRE ATT&CK techniques below are AI-generated suggestions, inferred from the description of the vulnerability by the CIRCL/vulnerability-attack-technique-classification-roberta-base model, served locally by ML-Gateway. They have not been verified by an analyst and are provided for guidance only.

Action not permitted

CVE-2026-64525 (GCVE-0-2026-64525)

GHSA-PHMC-55J6-972R

Tags

Sightings

Nomenclature