CVE-2026-53259 (GCVE-0-2026-53259)

Vulnerability from cvelistv5 – Published: 2026-06-25 08:39 – Updated: 2026-06-25 08:39
VLAI
Title
ipv6: anycast: insert aca into global hash under idev->lock
Summary
In the Linux kernel, the following vulnerability has been resolved: ipv6: anycast: insert aca into global hash under idev->lock syzbot reported a splat [1]: a slab-use-after-free in ipv6_chk_acast_addr(), which walks the global inet6_acaddr_lst[] hash under RCU and dereferences a struct ifacaddr6 that has already been freed while still linked in the hash, so a later reader walks into a dangling node. In __ipv6_dev_ac_inc() the aca is allocated with refcount 1, then aca_get() bumps it to 2 to keep it alive across the unlocked region. It is published to idev->ac_list under idev->lock, but ipv6_add_acaddr_hash() runs after write_unlock_bh(). A concurrent teardown (ipv6_ac_destroy_dev() from addrconf_ifdown(), under RTNL) can slip into that window: CPU0 __ipv6_dev_ac_inc CPU1 ipv6_ac_destroy_dev (RTNL) ------------------------------ ------------------------------------ aca_alloc() refcnt 1 aca_get() refcnt 2 write_lock_bh(idev->lock) add aca to ac_list write_unlock_bh(idev->lock) write_lock_bh(idev->lock) pull aca off ac_list write_unlock_bh(idev->lock) ipv6_del_acaddr_hash(aca) hlist_del_init_rcu() is a no-op, aca is not in the hash yet aca_put() refcnt 2->1 ipv6_add_acaddr_hash(aca) aca now inserted into the hash aca_put() refcnt 1->0 call_rcu(aca_free_rcu) -> kfree(aca) The hash removal becomes a no-op because the insertion has not happened yet, so once CPU0 inserts and drops the last reference, the aca is freed while still linked in inet6_acaddr_lst[], and readers dereference freed memory after the slab slot is reused. This window opened once RTNL stopped serializing the join path against device teardown. Move ipv6_add_acaddr_hash() inside the idev->lock section so the ac_list and hash insertions are atomic with respect to teardown: a racing remover now either misses the aca entirely or finds it in both lists. acaddr_hash_lock is now nested under idev->lock, which is acquired in softirq context, so switch all acaddr_hash_lock sites to spin_lock_bh() to avoid the irq lock inversion reported in [2]. [1] https://syzkaller.appspot.com/bug?extid=a01df04303c131efbf3a [2] https://lore.kernel.org/netdev/6a194ef7.ba3b1513.1890b4.0000.GAE@google.com/
Severity
No CVSS data available.
Assigner
References
Impacted products
Vendor Product Version
Linux Linux Affected: eb1ac9ff6c4a5720b1a1476233be374c5dc44bff , < 15be7e9fdbff831fb3e89b83cc337a4f85ad3310 (git)
Affected: eb1ac9ff6c4a5720b1a1476233be374c5dc44bff , < 3a967c498baa976b11d4800dda224c507416e97c (git)
Affected: eb1ac9ff6c4a5720b1a1476233be374c5dc44bff , < f723ccaff2fb72b71ae8a9fd283f0dee4d9ae7a3 (git)
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Linux Linux Affected: 6.17
Unaffected: 0 , < 6.17 (semver)
Unaffected: 6.18.36 , ≤ 6.18.* (semver)
Unaffected: 7.0.13 , ≤ 7.0.* (semver)
Unaffected: 7.1 , ≤ * (original_commit_for_fix)
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{
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      "affected": [
        {
          "defaultStatus": "unaffected",
          "product": "Linux",
          "programFiles": [
            "net/ipv6/anycast.c"
          ],
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          "vendor": "Linux",
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              "versionType": "semver"
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              "versionType": "semver"
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                  "criteria": "cpe:2.3:o:linux:linux_kernel:*:*:*:*:*:*:*:*",
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                  "versionStartIncluding": "6.17",
                  "vulnerable": true
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              "operator": "OR"
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      "descriptions": [
        {
          "lang": "en",
          "value": "In the Linux kernel, the following vulnerability has been resolved:\n\nipv6: anycast: insert aca into global hash under idev-\u003elock\n\nsyzbot reported a splat [1]: a slab-use-after-free in\nipv6_chk_acast_addr(), which walks the global inet6_acaddr_lst[] hash\nunder RCU and dereferences a struct ifacaddr6 that has already been\nfreed while still linked in the hash, so a later reader walks into a\ndangling node.\n\nIn __ipv6_dev_ac_inc() the aca is allocated with refcount 1, then\naca_get() bumps it to 2 to keep it alive across the unlocked region.\nIt is published to idev-\u003eac_list under idev-\u003elock, but\nipv6_add_acaddr_hash() runs after write_unlock_bh(). A concurrent\nteardown (ipv6_ac_destroy_dev() from addrconf_ifdown(), under RTNL)\ncan slip into that window:\n\n  CPU0 __ipv6_dev_ac_inc           CPU1 ipv6_ac_destroy_dev (RTNL)\n  ------------------------------   ------------------------------------\n  aca_alloc()              refcnt 1\n  aca_get()               refcnt 2\n  write_lock_bh(idev-\u003elock)\n    add aca to ac_list\n  write_unlock_bh(idev-\u003elock)\n                                   write_lock_bh(idev-\u003elock)\n                                     pull aca off ac_list\n                                   write_unlock_bh(idev-\u003elock)\n                                   ipv6_del_acaddr_hash(aca)\n                                     hlist_del_init_rcu() is a no-op,\n                                     aca is not in the hash yet\n                                   aca_put()           refcnt 2-\u003e1\n  ipv6_add_acaddr_hash(aca)\n    aca now inserted into the hash\n  aca_put()                refcnt 1-\u003e0\n    call_rcu(aca_free_rcu) -\u003e kfree(aca)\n\nThe hash removal becomes a no-op because the insertion has not\nhappened yet, so once CPU0 inserts and drops the last reference, the\naca is freed while still linked in inet6_acaddr_lst[], and readers\ndereference freed memory after the slab slot is reused.\n\nThis window opened once RTNL stopped serializing the join path against\ndevice teardown. Move ipv6_add_acaddr_hash() inside the idev-\u003elock\nsection so the ac_list and hash insertions are atomic with respect to\nteardown: a racing remover now either misses the aca entirely or finds\nit in both lists.\n\nacaddr_hash_lock is now nested under idev-\u003elock, which is acquired in\nsoftirq context, so switch all acaddr_hash_lock sites to spin_lock_bh()\nto avoid the irq lock inversion reported in [2].\n\n[1] https://syzkaller.appspot.com/bug?extid=a01df04303c131efbf3a\n[2] https://lore.kernel.org/netdev/6a194ef7.ba3b1513.1890b4.0000.GAE@google.com/"
        }
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      "providerMetadata": {
        "dateUpdated": "2026-06-25T08:39:48.571Z",
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        "shortName": "Linux"
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          "url": "https://git.kernel.org/stable/c/15be7e9fdbff831fb3e89b83cc337a4f85ad3310"
        },
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          "url": "https://git.kernel.org/stable/c/3a967c498baa976b11d4800dda224c507416e97c"
        },
        {
          "url": "https://git.kernel.org/stable/c/f723ccaff2fb72b71ae8a9fd283f0dee4d9ae7a3"
        }
      ],
      "title": "ipv6: anycast: insert aca into global hash under idev-\u003elock",
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    "assignerShortName": "Linux",
    "cveId": "CVE-2026-53259",
    "datePublished": "2026-06-25T08:39:48.571Z",
    "dateReserved": "2026-06-09T07:44:35.394Z",
    "dateUpdated": "2026-06-25T08:39:48.571Z",
    "state": "PUBLISHED"
  },
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      "cve": "CVE-2026-53259",
      "date": "2026-06-26",
      "epss": "0.00161",
      "percentile": "0.057"
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}


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Forecast uses a logistic model when the trend is rising, or an exponential decay model when the trend is falling. Fitted via linearized least squares.

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  • Seen: The vulnerability was mentioned, discussed, or observed by the user.
  • Confirmed: The vulnerability has been validated from an analyst's perspective.
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