CVE-2026-64027 (GCVE-0-2026-64027)

Vulnerability from cvelistv5 – Published: 2026-07-19 15:39 – Updated: 2026-08-05 12:38
VLAI
Title
net: shaper: rework the VALID marking (again)
Summary
In the Linux kernel, the following vulnerability has been resolved: net: shaper: rework the VALID marking (again) Recent commit changed the semantics from NOT_VALID to VALID. I didn't realize that the flags are not stored atomically with the entry in XArray. There's still a race of reader observing a VALID mark for a slot, getting interrupted, writer replacing the entry with a different one, reader continuing, fetching the entry which is now a different pointer than the pointer for which VALID was meant. The biggest consequence of this is that we may see a UAF since net_shaper_rollback() assumed that entries without VALID can be freed without observing RCU. Looks like the XArray marks are buying us nothing at this point. Let's convert the code to an explicit valid field. The smp_load_acquire() / smp_store_release() barriers are marginally cleaner.
Severity
7.8 (High)
CVSS:3.1/AV:L/AC:L/PR:L/UI:N/S:U/C:H/I:H/A:H
Assigner
Linux CNA under the mitre root
CNA scorecard D 54/100 over 6618 records in the last 180 days details
References
Impacted products
Vendor Product Version CPE status
Linux Linux Affected: 93954b40f6a4fc43226c01a15b02732f884500f1 , < 2417df5e7bb4184b9d3a2988036bf2c46e594545 (git)
Affected: 93954b40f6a4fc43226c01a15b02732f884500f1 , < 96ea960dd40fd55302e0fd755176f26a95e6a50c (git)
Affected: 93954b40f6a4fc43226c01a15b02732f884500f1 , < b8d7519352ba8c6df83259295d4a3bad093cae90 (git)
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Linux Linux Affected: 6.13
Unaffected: 0 , < 6.13 (semver)
Unaffected: 6.18.34 , ≤ 6.18.* (semver)
Unaffected: 7.0.11 , ≤ 7.0.* (semver)
Unaffected: 7.1 , ≤ * (original_commit_for_fix)
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{
  "containers": {
    "cna": {
      "affected": [
        {
          "defaultStatus": "unaffected",
          "product": "Linux",
          "programFiles": [
            "include/net/net_shaper.h",
            "net/shaper/shaper.c"
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          "value": "In the Linux kernel, the following vulnerability has been resolved:\n\nnet: shaper: rework the VALID marking (again)\n\nRecent commit changed the semantics from NOT_VALID to VALID.\nI didn\u0027t realize that the flags are not stored atomically\nwith the entry in XArray. There\u0027s still a race of reader\nobserving a VALID mark for a slot, getting interrupted,\nwriter replacing the entry with a different one, reader\ncontinuing, fetching the entry which is now a different\npointer than the pointer for which VALID was meant.\n\nThe biggest consequence of this is that we may see a UAF\nsince net_shaper_rollback() assumed that entries without\nVALID can be freed without observing RCU.\n\nLooks like the XArray marks are buying us nothing at this\npoint. Let\u0027s convert the code to an explicit valid field.\nThe smp_load_acquire() / smp_store_release() barriers are\nmarginally cleaner."
        }
      ],
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            "baseSeverity": "HIGH",
            "vectorString": "CVSS:3.1/AV:L/AC:L/PR:L/UI:N/S:U/C:H/I:H/A:H",
            "version": "3.1"
          },
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              "value": "AV:L - The vulnerability is reached only through the net-shaper generic netlink API (socket syscall), not via remote packet handling. This matches the kernel guidance for tc/netlink-style configuration subsystems.\nAC:L - The family sets parallel_ops, so an attacker can run concurrent SET/GROUP/DELETE and GET/dump requests to control both sides of the TOCTOU race. No attacker-uncontrollable memory layout or rare timing is required beyond issuing concurrent netlink operations.\nPR:L - Exploitation requires triggering net_shaper_rollback() via SET, GROUP, or DELETE, which are gated by GENL_ADMIN_PERM (CAP_NET_ADMIN). That capability is available to an unprivileged user inside a user network namespace, not only to init-namespace root.\nUI:N - Exploitation is fully programmatic through netlink messages and requires no victim interaction such as mounting a filesystem or opening a file.\nS:U - Impact is kernel heap corruption and privilege escalation within the same kernel; it does not cross a VM, container runtime, or IOMMU security boundary by itself.\nC:H - The commit explicitly identifies a use-after-free; concurrent RCU readers can dereference freed net_shaper objects, enabling arbitrary kernel memory disclosure via UAF exploitation.\nI:H - UAF on heap-allocated net_shaper structures can be leveraged for heap grooming and arbitrary write or control-flow hijack, consistent with standard kernel UAF impact.\nA:H - The UAF can cause kernel oops or panic on freed-object access during lookup, dump, or rollback, and matches kernel guidance that any UAF warrants High availability impact."
            }
          ]
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        "dateUpdated": "2026-08-05T12:38:22.063Z",
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        "shortName": "Linux"
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          "url": "https://git.kernel.org/stable/c/2417df5e7bb4184b9d3a2988036bf2c46e594545"
        },
        {
          "url": "https://git.kernel.org/stable/c/96ea960dd40fd55302e0fd755176f26a95e6a50c"
        },
        {
          "url": "https://git.kernel.org/stable/c/b8d7519352ba8c6df83259295d4a3bad093cae90"
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      "title": "net: shaper: rework the VALID marking (again)",
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    "assignerShortName": "Linux",
    "cveId": "CVE-2026-64027",
    "datePublished": "2026-07-19T15:39:18.470Z",
    "dateReserved": "2026-07-19T07:54:57.028Z",
    "dateUpdated": "2026-08-05T12:38:22.063Z",
    "state": "PUBLISHED"
  },
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  "vulnerability-lookup:meta": {
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      "date": "2026-10-11",
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      "percentile": "0.062"
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            "value": "In the Linux kernel, the following vulnerability has been resolved:\n\nnet: shaper: rework the VALID marking (again)\n\nRecent commit changed the semantics from NOT_VALID to VALID.\nI didn\u0027t realize that the flags are not stored atomically\nwith the entry in XArray. There\u0027s still a race of reader\nobserving a VALID mark for a slot, getting interrupted,\nwriter replacing the entry with a different one, reader\ncontinuing, fetching the entry which is now a different\npointer than the pointer for which VALID was meant.\n\nThe biggest consequence of this is that we may see a UAF\nsince net_shaper_rollback() assumed that entries without\nVALID can be freed without observing RCU.\n\nLooks like the XArray marks are buying us nothing at this\npoint. Let\u0027s convert the code to an explicit valid field.\nThe smp_load_acquire() / smp_store_release() barriers are\nmarginally cleaner."
          }
        ],
        "id": "CVE-2026-64027",
        "lastModified": "2026-07-30T14:59:47.950",
        "metrics": {
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                "attackVector": "LOCAL",
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                "baseSeverity": "HIGH",
                "confidentialityImpact": "HIGH",
                "integrityImpact": "HIGH",
                "privilegesRequired": "LOW",
                "scope": "UNCHANGED",
                "userInteraction": "NONE",
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              "source": "416baaa9-dc9f-4396-8d5f-8c081fb06d67",
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      "current_release_date": "2026-08-05T14:20:31+00:00",
      "cve": "CVE-2026-64027",
      "id": "CVE-2026-64027",
      "initial_release_date": "2026-07-19T00:00:00+00:00",
      "product_status:known_affected": "184",
      "product_status:known_not_affected": "91",
      "source": "Red Hat CSAF VEX",
      "status": "final",
      "title": "kernel: net: shaper: rework the VALID marking (again)",
      "url": "https://security.access.redhat.com/data/csaf/v2/vex/2026/cve-2026-64027.json",
      "version": "3"
    },
    "suse_vex": {
      "aggregate_severity": "important",
      "current_release_date": "2026-09-15T01:57:06Z",
      "cve": "CVE-2026-64027",
      "id": "CVE-2026-64027",
      "initial_release_date": "2026-07-21T13:01:14Z",
      "product_status:known_affected": "29",
      "product_status:known_not_affected": "345",
      "source": "SUSE CSAF VEX",
      "status": "interim",
      "title": "SUSE CVE CVE-2026-64027",
      "url": "https://ftp.suse.com/pub/projects/security/csaf-vex/cve-2026-64027.json",
      "version": "5"
    }
  }
}



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