CVE-2026-64538 (GCVE-0-2026-64538)

Vulnerability from cvelistv5 – Published: 2026-07-27 20:10 – Updated: 2026-07-27 20:10
VLAI
Title
ipv6: Fix null-ptr-deref in fib6_nh_mtu_change().
Summary
In the Linux kernel, the following vulnerability has been resolved: ipv6: Fix null-ptr-deref in fib6_nh_mtu_change(). fib6_nh_mtu_change() re-fetches idev via __in6_dev_get(arg->dev) and dereferences idev->cnf.mtu6 without a NULL check. addrconf_ifdown() clears dev->ip6_ptr with RCU_INIT_POINTER() after rt6_disable_ip() has released tb6_lock, so the RA-driven MTU walk can observe a NULL idev and oops. The caller rt6_mtu_change_route() guards its own __in6_dev_get(), but this re-fetch is unguarded; nexthop-backed routes survive addrconf_ifdown()'s flush, so the walk still reaches it after ip6_ptr is nulled. Return 0 when idev is NULL, matching rt6_mtu_change_route() and the fib6_mtu() fix in commit 5ad509c1fdad ("ipv6: Fix null-ptr-deref in fib6_mtu()."). Oops: general protection fault, ... KASAN: null-ptr-deref in range [0x00000000000002a8-0x00000000000002af] RIP: 0010:fib6_nh_mtu_change+0x203/0x990 rt6_mtu_change_route+0x141/0x1d0 __fib6_clean_all+0xd0/0x160 rt6_mtu_change+0xb4/0x100 ndisc_router_discovery+0x24b5/0x2cb0 icmpv6_rcv+0x12e9/0x1710 ipv6_rcv+0x39b/0x410
Severity
No CVSS data available.
Assigner
References
Impacted products
Vendor Product Version
Linux Linux Affected: c0b220cf7d80eb8a36ae9f12cae6df4577a6814e , < d08d019f2f43a6f9a71e81868bbc326b3afaf37b (git)
Affected: c0b220cf7d80eb8a36ae9f12cae6df4577a6814e , < 1451deca9896957159f0666520a792c1b861af4f (git)
Affected: c0b220cf7d80eb8a36ae9f12cae6df4577a6814e , < b2c70dd3326809429b709a9c7e9220d29923051a (git)
Affected: c0b220cf7d80eb8a36ae9f12cae6df4577a6814e , < 302d57ed7872838b40e56a868fb4c7da7da606e9 (git)
Affected: c0b220cf7d80eb8a36ae9f12cae6df4577a6814e , < 80600b5d0f3ecb9324120dc95b5e915130f516c5 (git)
Affected: c0b220cf7d80eb8a36ae9f12cae6df4577a6814e , < b0d0eb13a0441a8ebf4f227843deaf494f1e2c33 (git)
Affected: c0b220cf7d80eb8a36ae9f12cae6df4577a6814e , < 6428634f7a0b7878144b4925c37856bef3224967 (git)
Affected: c0b220cf7d80eb8a36ae9f12cae6df4577a6814e , < 46c3b8191aad3d032776bf3bebf03efdf5f4b905 (git)
Create a notification for this product.
Linux Linux Affected: 5.3
Unaffected: 0 , < 5.3 (semver)
Unaffected: 5.10.261 , ≤ 5.10.* (semver)
Unaffected: 5.15.212 , ≤ 5.15.* (semver)
Unaffected: 6.1.178 , ≤ 6.1.* (semver)
Unaffected: 6.6.145 , ≤ 6.6.* (semver)
Unaffected: 6.12.97 , ≤ 6.12.* (semver)
Unaffected: 6.18.40 , ≤ 6.18.* (semver)
Unaffected: 7.1.5 , ≤ 7.1.* (semver)
Unaffected: 7.2-rc1 , ≤ * (original_commit_for_fix)
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        {
          "lang": "en",
          "value": "In the Linux kernel, the following vulnerability has been resolved:\n\nipv6: Fix null-ptr-deref in fib6_nh_mtu_change().\n\nfib6_nh_mtu_change() re-fetches idev via __in6_dev_get(arg-\u003edev) and\ndereferences idev-\u003ecnf.mtu6 without a NULL check. addrconf_ifdown()\nclears dev-\u003eip6_ptr with RCU_INIT_POINTER() after rt6_disable_ip() has\nreleased tb6_lock, so the RA-driven MTU walk can observe a NULL idev and\noops. The caller rt6_mtu_change_route() guards its own __in6_dev_get(),\nbut this re-fetch is unguarded; nexthop-backed routes survive\naddrconf_ifdown()\u0027s flush, so the walk still reaches it after ip6_ptr is\nnulled.\n\nReturn 0 when idev is NULL, matching rt6_mtu_change_route() and the\nfib6_mtu() fix in commit 5ad509c1fdad (\"ipv6: Fix null-ptr-deref in\nfib6_mtu().\").\n\n  Oops: general protection fault, ... KASAN: null-ptr-deref in range\n        [0x00000000000002a8-0x00000000000002af]\n  RIP: 0010:fib6_nh_mtu_change+0x203/0x990\n   rt6_mtu_change_route+0x141/0x1d0\n   __fib6_clean_all+0xd0/0x160\n   rt6_mtu_change+0xb4/0x100\n   ndisc_router_discovery+0x24b5/0x2cb0\n   icmpv6_rcv+0x12e9/0x1710\n   ipv6_rcv+0x39b/0x410"
        }
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      "providerMetadata": {
        "dateUpdated": "2026-07-27T20:10:32.779Z",
        "orgId": "416baaa9-dc9f-4396-8d5f-8c081fb06d67",
        "shortName": "Linux"
      },
      "references": [
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          "url": "https://git.kernel.org/stable/c/d08d019f2f43a6f9a71e81868bbc326b3afaf37b"
        },
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          "url": "https://git.kernel.org/stable/c/1451deca9896957159f0666520a792c1b861af4f"
        },
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          "url": "https://git.kernel.org/stable/c/80600b5d0f3ecb9324120dc95b5e915130f516c5"
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          "url": "https://git.kernel.org/stable/c/b0d0eb13a0441a8ebf4f227843deaf494f1e2c33"
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        {
          "url": "https://git.kernel.org/stable/c/6428634f7a0b7878144b4925c37856bef3224967"
        },
        {
          "url": "https://git.kernel.org/stable/c/46c3b8191aad3d032776bf3bebf03efdf5f4b905"
        }
      ],
      "title": "ipv6: Fix null-ptr-deref in fib6_nh_mtu_change().",
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    "assignerShortName": "Linux",
    "cveId": "CVE-2026-64538",
    "datePublished": "2026-07-27T20:10:32.779Z",
    "dateReserved": "2026-07-19T15:36:31.795Z",
    "dateUpdated": "2026-07-27T20:10:32.779Z",
    "state": "PUBLISHED"
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The caller rt6_mtu_change_route() guards its own __in6_dev_get(),\\nbut this re-fetch is unguarded; nexthop-backed routes survive\\naddrconf_ifdown()\u0027s flush, so the walk still reaches it after ip6_ptr is\\nnulled.\\n\\nReturn 0 when idev is NULL, matching rt6_mtu_change_route() and the\\nfib6_mtu() fix in commit 5ad509c1fdad (\\\"ipv6: Fix null-ptr-deref in\\nfib6_mtu().\\\").\\n\\n  Oops: general protection fault, ... KASAN: null-ptr-deref in range\\n        [0x00000000000002a8-0x00000000000002af]\\n  RIP: 0010:fib6_nh_mtu_change+0x203/0x990\\n   rt6_mtu_change_route+0x141/0x1d0\\n   __fib6_clean_all+0xd0/0x160\\n   rt6_mtu_change+0xb4/0x100\\n   ndisc_router_discovery+0x24b5/0x2cb0\\n   icmpv6_rcv+0x12e9/0x1710\\n   ipv6_rcv+0x39b/0x410\"}],\"affected\":[{\"source\":\"416baaa9-dc9f-4396-8d5f-8c081fb06d67\",\"affectedData\":[{\"vendor\":\"Linux\",\"product\":\"Linux\",\"defaultStatus\":\"unaffected\",\"programFiles\":[\"net/ipv6/route.c\"],\"repo\":\"https://git.kernel.org/pub/scm/linux/kernel/git/stable/linux.git\",\"versions\":[{\"version\":\"c0b220cf7d80eb8a36ae9f12cae6df4577a6814e\",\"lessThan\":\"d08d019f2f43a6f9a71e81868bbc326b3afaf37b\",\"versionType\":\"git\",\"status\":\"affected\"},{\"version\":\"c0b220cf7d80eb8a36ae9f12cae6df4577a6814e\",\"lessThan\":\"1451deca9896957159f0666520a792c1b861af4f\",\"versionType\":\"git\",\"status\":\"affected\"},{\"version\":\"c0b220cf7d80eb8a36ae9f12cae6df4577a6814e\",\"lessThan\":\"b2c70dd3326809429b709a9c7e9220d29923051a\",\"versionType\":\"git\",\"status\":\"affected\"},{\"version\":\"c0b220cf7d80eb8a36ae9f12cae6df4577a6814e\",\"lessThan\":\"302d57ed7872838b40e56a868fb4c7da7da606e9\",\"versionType\":\"git\",\"status\":\"affected\"},{\"version\":\"c0b220cf7d80eb8a36ae9f12cae6df4577a6814e\",\"lessThan\":\"80600b5d0f3ecb9324120dc95b5e915130f516c5\",\"versionType\":\"git\",\"status\":\"affected\"},{\"version\":\"c0b220cf7d80eb8a36ae9f12cae6df4577a6814e\",\"lessThan\":\"b0d0eb13a0441a8ebf4f227843deaf494f1e2c33\",\"versionType\":\"git\",\"status\":\"affected\"},{\"version\":\"c0b220cf7d80eb8a36ae9f12cae6df4577a6814e\",\"lessThan\":\"6428634f7a0b7878144b4925c37856bef3224967\",\"versionType\":\"git\",\"status\":\"affected\"},{\"version\":\"c0b220cf7d80eb8a36ae9f12cae6df4577a6814e\",\"lessThan\":\"46c3b8191aad3d032776bf3bebf03efdf5f4b905\",\"versionType\":\"git\",\"status\":\"affected\"}]},{\"vendor\":\"Linux\",\"product\":\"Linux\",\"defaultStatus\":\"affected\",\"programFiles\":[\"net/ipv6/route.c\"],\"repo\":\"https://git.kernel.org/pub/scm/linux/kernel/git/stable/linux.git\",\"versions\":[{\"version\":\"5.3\",\"status\":\"affected\"},{\"version\":\"0\",\"lessThan\":\"5.3\",\"versionType\":\"semver\",\"status\":\"unaffected\"},{\"version\":\"5.10.261\",\"lessThanOrEqual\":\"5.10.*\",\"versionType\":\"semver\",\"status\":\"unaffected\"},{\"version\":\"5.15.212\",\"lessThanOrEqual\":\"5.15.*\",\"versionType\":\"semver\",\"status\":\"unaffected\"},{\"version\":\"6.1.178\",\"lessThanOrEqual\":\"6.1.*\",\"versionType\":\"semver\",\"status\":\"unaffected\"},{\"version\":\"6.6.145\",\"lessThanOrEqual\":\"6.6.*\",\"versionType\":\"semver\",\"status\":\"unaffected\"},{\"version\":\"6.12.97\",\"lessThanOrEqual\":\"6.12.*\",\"versionType\":\"semver\",\"status\":\"unaffected\"},{\"version\":\"6.18.40\",\"lessThanOrEqual\":\"6.18.*\",\"versionType\":\"semver\",\"status\":\"unaffected\"},{\"version\":\"7.1.5\",\"lessThanOrEqual\":\"7.1.*\",\"versionType\":\"semver\",\"status\":\"unaffected\"},{\"version\":\"7.2-rc1\",\"lessThanOrEqual\":\"*\",\"versionType\":\"original_commit_for_fix\",\"status\":\"unaffected\"}]}]}],\"metrics\":{},\"references\":[{\"url\":\"https://git.kernel.org/stable/c/1451deca9896957159f0666520a792c1b861af4f\",\"source\":\"416baaa9-dc9f-4396-8d5f-8c081fb06d67\"},{\"url\":\"https://git.kernel.org/stable/c/302d57ed7872838b40e56a868fb4c7da7da606e9\",\"source\":\"416baaa9-dc9f-4396-8d5f-8c081fb06d67\"},{\"url\":\"https://git.kernel.org/stable/c/46c3b8191aad3d032776bf3bebf03efdf5f4b905\",\"source\":\"416baaa9-dc9f-4396-8d5f-8c081fb06d67\"},{\"url\":\"https://git.kernel.org/stable/c/6428634f7a0b7878144b4925c37856bef3224967\",\"source\":\"416baaa9-dc9f-4396-8d5f-8c081fb06d67\"},{\"url\":\"https://git.kernel.org/stable/c/80600b5d0f3ecb9324120dc95b5e915130f516c5\",\"source\":\"416baaa9-dc9f-4396-8d5f-8c081fb06d67\"},{\"url\":\"https://git.kernel.org/stable/c/b0d0eb13a0441a8ebf4f227843deaf494f1e2c33\",\"source\":\"416baaa9-dc9f-4396-8d5f-8c081fb06d67\"},{\"url\":\"https://git.kernel.org/stable/c/b2c70dd3326809429b709a9c7e9220d29923051a\",\"source\":\"416baaa9-dc9f-4396-8d5f-8c081fb06d67\"},{\"url\":\"https://git.kernel.org/stable/c/d08d019f2f43a6f9a71e81868bbc326b3afaf37b\",\"source\":\"416baaa9-dc9f-4396-8d5f-8c081fb06d67\"}]}}"
  }
}



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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.

Sightings

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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.
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  • 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.
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Detection rules are retrieved from Rulezet.