CVE-2026-74634 (GCVE-0-2026-74634)

Vulnerability from cvelistv5 – Published: 2026-08-22 15:32 – Updated: 2026-08-25 05:40
VLAI
Title
ring-buffer: Prevent subbuf order change when resizing is disabled
Summary
In the Linux kernel, the following vulnerability has been resolved: ring-buffer: Prevent subbuf order change when resizing is disabled Because ring_buffer_subbuf_order_set() frees buffer pages, we can't allow it when resizing is disabled. A non-consuming reader is at risk of use-after-free (rb_advance_iter()). Return -EBUSY on resize_disabled, matching ring_buffer_resize() behaviour.
Severity
7.8 (High)
CVSS:3.1/AV:L/AC:L/PR:L/UI:N/S:U/C:H/I:H/A:H
Assigner
References
Impacted products
Vendor Product Version CPE status
Linux Linux Affected: f9b94daa542a8d2532f0930f01cd9aec2d19621b , < b45b91db41379ee5fb36c187d6d7c37b725cbe8e (git)
Affected: f9b94daa542a8d2532f0930f01cd9aec2d19621b , < 62978cf6347972c04130e4e841ba404504d92b32 (git)
Affected: f9b94daa542a8d2532f0930f01cd9aec2d19621b , < 7568e9e717e7540bd05bcc007f5d76fcaff3cdff (git)
Affected: f9b94daa542a8d2532f0930f01cd9aec2d19621b , < bf98d7b0d5a99991e47e66cee4eb1d3fa514be97 (git)
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Linux Linux Affected: 6.8
Unaffected: 0 , < 6.8 (semver)
Unaffected: 6.12.104 , ≤ 6.12.* (semver)
Unaffected: 6.18.45 , ≤ 6.18.* (semver)
Unaffected: 7.1.9 , ≤ 7.1.* (semver)
Unaffected: 7.2 , ≤ * (original_commit_for_fix)
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{
  "containers": {
    "cna": {
      "affected": [
        {
          "defaultStatus": "unaffected",
          "product": "Linux",
          "programFiles": [
            "kernel/trace/ring_buffer.c"
          ],
          "repo": "https://git.kernel.org/pub/scm/linux/kernel/git/stable/linux.git",
          "vendor": "Linux",
          "versions": [
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              "status": "affected",
              "version": "f9b94daa542a8d2532f0930f01cd9aec2d19621b",
              "versionType": "git"
            },
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              "lessThan": "62978cf6347972c04130e4e841ba404504d92b32",
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              "versionType": "git"
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              "status": "unaffected",
              "version": "0",
              "versionType": "semver"
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              "versionType": "semver"
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              "versionType": "original_commit_for_fix"
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      ],
      "cpeApplicability": [
        {
          "nodes": [
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                  "criteria": "cpe:2.3:o:linux:linux_kernel:*:*:*:*:*:*:*:*",
                  "versionEndExcluding": "6.12.104",
                  "versionStartIncluding": "6.8",
                  "vulnerable": true
                },
                {
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                  "versionEndExcluding": "6.18.45",
                  "versionStartIncluding": "6.8",
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                  "vulnerable": true
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                  "versionEndExcluding": "7.2",
                  "versionStartIncluding": "6.8",
                  "vulnerable": true
                }
              ],
              "negate": false,
              "operator": "OR"
            }
          ]
        }
      ],
      "descriptions": [
        {
          "lang": "en",
          "value": "In the Linux kernel, the following vulnerability has been resolved:\n\nring-buffer: Prevent subbuf order change when resizing is disabled\n\nBecause ring_buffer_subbuf_order_set() frees buffer pages, we can\u0027t\nallow it when resizing is disabled. A non-consuming reader is at risk of\nuse-after-free (rb_advance_iter()).\n\nReturn -EBUSY on resize_disabled, matching ring_buffer_resize()\nbehaviour."
        }
      ],
      "metrics": [
        {
          "cvssV3_1": {
            "baseScore": 7.8,
            "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"
          },
          "scenarios": [
            {
              "lang": "en",
              "value": "AV:L - The bug is reached only via local tracefs operations: write() to buffer_subbuf_size_kb (buffer_subbuf_size_write) while a non-consuming ring_buffer_read_start() iterator is active from reading trace/per_cpu/cpuN/trace. No network, adjacent-radio, or physical-device path reaches ring_buffer_subbuf_order_set().\nAC:L - The attacker controls both sides: one thread holds trace open for read (sets resize_disabled via ring_buffer_read_start) while another writes buffer_subbuf_size_kb to free pages still referenced by iter-\u003ehead_page. rb_advance_iter()/rb_inc_iter then dereferences freed memory; the race is reliably retried.\nPR:L - tracing_check_open_get_tr() enforces only LOCKDOWN_TRACEFS and DAC with no capability check. tracefs buffer_subbuf_size_kb and trace are mode 0640 and are routinely delegated via gid=/mode= to tracing-group members on Android/Perfetto, ChromeOS, and developer systems, matching prior CNA tracefs UAF scores (CVE-2024-50207, CVE-2025-38101).\nUI:N - Exploitation uses the attacker\u0027s own tracefs file descriptors and threads (open trace for read, write buffer_subbuf_size_kb). No separate victim mount, click, or configuration action is required beyond the attacker holding tracefs access.\nS:U - The use-after-free corrupts kernel ring-buffer heap pages and metadata within the same OS security authority. It enables local privilege escalation but does not cross VM, IOMMU, container, or hardware trust boundaries.\nC:H - ring_buffer_subbuf_order_set() frees buffer_page data pages while iterators retain head_page pointers; rb_iter_head_event() memcpy() and rb_inc_iter() read iter-\u003ehead_page-\u003epage after free_pages(), leaking recycled kernel heap contents to userspace through trace reads.\nI:H - Freed sub-buffer pages and buffer_page structures can be reused while iterators and splice paths still perform stores and list operations on them. This UAF heap corruption is exploitable for arbitrary kernel writes and control-flow hijack, not merely a crash.\nA:H - Concurrent page frees with active iterators corrupt ring-buffer lists and cause use-after-free dereferences in rb_advance_iter(), producing kernel oopses/panics. syzbot reported this failure mode and the attacker can retrigger it at will."
            }
          ]
        }
      ],
      "providerMetadata": {
        "dateUpdated": "2026-08-25T05:40:58.185Z",
        "orgId": "416baaa9-dc9f-4396-8d5f-8c081fb06d67",
        "shortName": "Linux"
      },
      "references": [
        {
          "url": "https://git.kernel.org/stable/c/b45b91db41379ee5fb36c187d6d7c37b725cbe8e"
        },
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          "url": "https://git.kernel.org/stable/c/62978cf6347972c04130e4e841ba404504d92b32"
        },
        {
          "url": "https://git.kernel.org/stable/c/7568e9e717e7540bd05bcc007f5d76fcaff3cdff"
        },
        {
          "url": "https://git.kernel.org/stable/c/bf98d7b0d5a99991e47e66cee4eb1d3fa514be97"
        }
      ],
      "title": "ring-buffer: Prevent subbuf order change when resizing is disabled",
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  },
  "cveMetadata": {
    "assignerOrgId": "416baaa9-dc9f-4396-8d5f-8c081fb06d67",
    "assignerShortName": "Linux",
    "cveId": "CVE-2026-74634",
    "datePublished": "2026-08-22T15:32:14.547Z",
    "dateReserved": "2026-08-15T05:44:03.922Z",
    "dateUpdated": "2026-08-25T05:40:58.185Z",
    "state": "PUBLISHED"
  },
  "dataType": "CVE_RECORD",
  "dataVersion": "5.2",
  "vulnerability-lookup:meta": {
    "epss": {
      "cve": "CVE-2026-74634",
      "date": "2026-08-29",
      "epss": "0.00125",
      "percentile": "0.02486"
    },
    "nvd": "{\"cve\":{\"id\":\"CVE-2026-74634\",\"sourceIdentifier\":\"416baaa9-dc9f-4396-8d5f-8c081fb06d67\",\"published\":\"2026-08-22T16:16:36.487\",\"lastModified\":\"2026-08-25T06:18:42.647\",\"vulnStatus\":\"Received\",\"cveTags\":[],\"descriptions\":[{\"lang\":\"en\",\"value\":\"In the Linux kernel, the following vulnerability has been resolved:\\n\\nring-buffer: Prevent subbuf order change when resizing is disabled\\n\\nBecause ring_buffer_subbuf_order_set() frees buffer pages, we can\u0027t\\nallow it when resizing is disabled. A non-consuming reader is at risk of\\nuse-after-free (rb_advance_iter()).\\n\\nReturn -EBUSY on resize_disabled, matching ring_buffer_resize()\\nbehaviour.\"}],\"affected\":[{\"source\":\"416baaa9-dc9f-4396-8d5f-8c081fb06d67\",\"affectedData\":[{\"vendor\":\"Linux\",\"product\":\"Linux\",\"defaultStatus\":\"unaffected\",\"programFiles\":[\"kernel/trace/ring_buffer.c\"],\"repo\":\"https://git.kernel.org/pub/scm/linux/kernel/git/stable/linux.git\",\"versions\":[{\"version\":\"f9b94daa542a8d2532f0930f01cd9aec2d19621b\",\"lessThan\":\"b45b91db41379ee5fb36c187d6d7c37b725cbe8e\",\"versionType\":\"git\",\"status\":\"affected\"},{\"version\":\"f9b94daa542a8d2532f0930f01cd9aec2d19621b\",\"lessThan\":\"62978cf6347972c04130e4e841ba404504d92b32\",\"versionType\":\"git\",\"status\":\"affected\"},{\"version\":\"f9b94daa542a8d2532f0930f01cd9aec2d19621b\",\"lessThan\":\"7568e9e717e7540bd05bcc007f5d76fcaff3cdff\",\"versionType\":\"git\",\"status\":\"affected\"},{\"version\":\"f9b94daa542a8d2532f0930f01cd9aec2d19621b\",\"lessThan\":\"bf98d7b0d5a99991e47e66cee4eb1d3fa514be97\",\"versionType\":\"git\",\"status\":\"affected\"}]},{\"vendor\":\"Linux\",\"product\":\"Linux\",\"defaultStatus\":\"affected\",\"programFiles\":[\"kernel/trace/ring_buffer.c\"],\"repo\":\"https://git.kernel.org/pub/scm/linux/kernel/git/stable/linux.git\",\"versions\":[{\"version\":\"6.8\",\"status\":\"affected\"},{\"version\":\"0\",\"lessThan\":\"6.8\",\"versionType\":\"semver\",\"status\":\"unaffected\"},{\"version\":\"6.12.104\",\"lessThanOrEqual\":\"6.12.*\",\"versionType\":\"semver\",\"status\":\"unaffected\"},{\"version\":\"6.18.45\",\"lessThanOrEqual\":\"6.18.*\",\"versionType\":\"semver\",\"status\":\"unaffected\"},{\"version\":\"7.1.9\",\"lessThanOrEqual\":\"7.1.*\",\"versionType\":\"semver\",\"status\":\"unaffected\"},{\"version\":\"7.2\",\"lessThanOrEqual\":\"*\",\"versionType\":\"original_commit_for_fix\",\"status\":\"unaffected\"}]}]}],\"metrics\":{\"cvssMetricV31\":[{\"source\":\"416baaa9-dc9f-4396-8d5f-8c081fb06d67\",\"type\":\"Secondary\",\"cvssData\":{\"version\":\"3.1\",\"vectorString\":\"CVSS:3.1/AV:L/AC:L/PR:L/UI:N/S:U/C:H/I:H/A:H\",\"baseScore\":7.8,\"baseSeverity\":\"HIGH\",\"attackVector\":\"LOCAL\",\"attackComplexity\":\"LOW\",\"privilegesRequired\":\"LOW\",\"userInteraction\":\"NONE\",\"scope\":\"UNCHANGED\",\"confidentialityImpact\":\"HIGH\",\"integrityImpact\":\"HIGH\",\"availabilityImpact\":\"HIGH\"},\"exploitabilityScore\":1.8,\"impactScore\":5.9}]},\"references\":[{\"url\":\"https://git.kernel.org/stable/c/62978cf6347972c04130e4e841ba404504d92b32\",\"source\":\"416baaa9-dc9f-4396-8d5f-8c081fb06d67\"},{\"url\":\"https://git.kernel.org/stable/c/7568e9e717e7540bd05bcc007f5d76fcaff3cdff\",\"source\":\"416baaa9-dc9f-4396-8d5f-8c081fb06d67\"},{\"url\":\"https://git.kernel.org/stable/c/b45b91db41379ee5fb36c187d6d7c37b725cbe8e\",\"source\":\"416baaa9-dc9f-4396-8d5f-8c081fb06d67\"},{\"url\":\"https://git.kernel.org/stable/c/bf98d7b0d5a99991e47e66cee4eb1d3fa514be97\",\"source\":\"416baaa9-dc9f-4396-8d5f-8c081fb06d67\"}]}}",
    "redhat_vex": {
      "aggregate_severity": "Moderate",
      "current_release_date": "2026-08-25T08:52:31+00:00",
      "cve": "CVE-2026-74634",
      "id": "CVE-2026-74634",
      "initial_release_date": "2026-08-22T00:00:00+00:00",
      "product_status:known_affected": "76",
      "product_status:known_not_affected": "198",
      "source": "Red Hat CSAF VEX",
      "status": "final",
      "title": "kernel: ring-buffer: Prevent subbuf order change when resizing is disabled",
      "url": "https://security.access.redhat.com/data/csaf/v2/vex/2026/cve-2026-74634.json",
      "version": "3"
    }
  }
}



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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.
  • 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.