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CVE-2026-89571 (GCVE-0-2026-89571)

Vulnerability from cvelistv5 – Published: 2026-09-11 19:44 – Updated: 2026-09-13 06:31
VLAI
Title
cxl/features: bound fwctl command payload to the input buffer
Summary
In the Linux kernel, the following vulnerability has been resolved: cxl/features: bound fwctl command payload to the input buffer fwctl_cmd_rpc() copies cmd->in_len bytes into inbuf = kvzalloc(cmd->in_len) and passes inbuf and in_len to ->fw_rpc(). The CXL callback cxlctl_fw_rpc() ignores in_len and never checks the user-controlled op_size against it. cxlctl_set_feature() bounds op_size only from below (op_size <= sizeof(feat_in->hdr)) and then reads op_size - sizeof(hdr) bytes from feat_in->feat_data via cxl_set_feature(). With a small in_len and a large op_size the first memcpy() already reads past the kvzalloc(in_len) buffer; the out-of-bounds bytes are placed in the mailbox payload and sent to the device, and a large enough op_size can walk into unmapped memory and oops the kernel. The Get paths pin op_size to a fixed size but likewise read the input struct without checking in_len. Reject, at the single dispatch point, any request whose fixed header plus op_size does not fit in the copied-in buffer. The lower-bound test guards the subtraction and ensures op_size was copied in before it is read.
Severity
7.1 (High)
CVSS:3.1/AV:L/AC:L/PR:L/UI:N/S:U/C:H/I:N/A:H
Assigner
References
Impacted products
Vendor Product Version CPE status
Linux Linux Affected: eb5dfcb9e36d0e46089fec777d911313c1876fa3 , < 14d52c15d5d99477b20a2d61fe36f347080da6cd (git)
Affected: eb5dfcb9e36d0e46089fec777d911313c1876fa3 , < d8957545fe96f7905791c937758ebfc1ae1e5b17 (git)
Affected: eb5dfcb9e36d0e46089fec777d911313c1876fa3 , < f687394af983df5660b6afae7e0d06969f3af206 (git)
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Linux Linux Affected: 6.15
Unaffected: 0 , < 6.15 (semver)
Unaffected: 6.18.50 , ≤ 6.18.* (semver)
Unaffected: 7.2.4 , ≤ 7.2.* (semver)
Unaffected: 7.3-rc1 , ≤ * (original_commit_for_fix)
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{
  "containers": {
    "cna": {
      "affected": [
        {
          "defaultStatus": "unaffected",
          "product": "Linux",
          "programFiles": [
            "drivers/cxl/core/features.c"
          ],
          "repo": "https://git.kernel.org/pub/scm/linux/kernel/git/stable/linux.git",
          "vendor": "Linux",
          "versions": [
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          "vendor": "Linux",
          "versions": [
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              "version": "7.2.4",
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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\ncxl/features: bound fwctl command payload to the input buffer\n\nfwctl_cmd_rpc() copies cmd-\u003ein_len bytes into inbuf = kvzalloc(cmd-\u003ein_len)\nand passes inbuf and in_len to -\u003efw_rpc(). The CXL callback cxlctl_fw_rpc()\nignores in_len and never checks the user-controlled op_size against it.\n\ncxlctl_set_feature() bounds op_size only from below\n(op_size \u003c= sizeof(feat_in-\u003ehdr)) and then reads op_size - sizeof(hdr)\nbytes from feat_in-\u003efeat_data via cxl_set_feature(). With a small in_len\nand a large op_size the first memcpy() already reads past the\nkvzalloc(in_len) buffer; the out-of-bounds bytes are placed in the mailbox\npayload and sent to the device, and a large enough op_size can walk into\nunmapped memory and oops the kernel. The Get paths pin op_size to a fixed\nsize but likewise read the input struct without checking in_len.\n\nReject, at the single dispatch point, any request whose fixed header plus\nop_size does not fit in the copied-in buffer. The lower-bound test guards\nthe subtraction and ensures op_size was copied in before it is read."
        }
      ],
      "metrics": [
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            "baseSeverity": "HIGH",
            "vectorString": "CVSS:3.1/AV:L/AC:L/PR:L/UI:N/S:U/C:H/I:N/A:H",
            "version": "3.1"
          },
          "scenarios": [
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              "lang": "en",
              "value": "AV:L - The bug is reached only via local ioctl(FWCTL_RPC) on /dev/fwctl/fwctlN through fwctl_fops_ioctl()-\u003efwctl_cmd_rpc()-\u003ecxlctl_fw_rpc(); CXL features/fwctl has no network, adjacent-radio, or physical-bus entry point.\nAC:L - The attacker fully controls fwctl_rpc.in_len and fwctl_rpc_cxl.op_size; a short in_len with a large op_size, or in_len=0, deterministically over-reads the kvzalloc buffer or dereferences ZERO_SIZE_PTR. No race or attacker-uncontrollable layout is required.\nPR:L - GET commands run at FWCTL_RPC_CONFIGURATION with no capability check, and SET_FEATURE for reset-effect features needs only FWCTL_RPC_DEBUG_WRITE (no CAP_SYS_RAWIO). Per CNA fwctl precedent, /dev/fwctl access is routinely granted to management/VMM users without init-namespace root.\nUI:N - The attacker opens the fwctl device and issues the RPC ioctl themselves; no victim action such as mounting a filesystem or opening a file is required.\nS:U - The heap over-read, mailbox copy, and any oops stay inside the host kernel CXL/fwctl code. This is ordinary same-host kernel impact, not a VM escape, IOMMU bypass, or other changed-scope boundary.\nC:H - cxl_set_feature() memcpy()s attacker-chosen op_size bytes from past the kvzalloc(in_len) buffer into the CXL mailbox and to the device; that unbounded kernel-heap over-read is C:H per kernel CNA guidance, and GET_FEATURE can return stored feature data including leaked heap.\nI:N - The defect is a read-only over-read into a newly allocated mailbox buffer sent to the device; there is no kernel out-of-bounds write, use-after-free, or control-flow hijack primitive.\nA:H - A large op_size walks from the short kvzalloc buffer into unmapped memory and oopses, and in_len=0 makes kvzalloc return ZERO_SIZE_PTR so reading opcode faults; either path panics the kernel and is repeatable at will."
            }
          ]
        }
      ],
      "providerMetadata": {
        "dateUpdated": "2026-09-13T06:31:09.007Z",
        "orgId": "416baaa9-dc9f-4396-8d5f-8c081fb06d67",
        "shortName": "Linux"
      },
      "references": [
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          "url": "https://git.kernel.org/stable/c/14d52c15d5d99477b20a2d61fe36f347080da6cd"
        },
        {
          "url": "https://git.kernel.org/stable/c/d8957545fe96f7905791c937758ebfc1ae1e5b17"
        },
        {
          "url": "https://git.kernel.org/stable/c/f687394af983df5660b6afae7e0d06969f3af206"
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      "title": "cxl/features: bound fwctl command payload to the input buffer",
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    "assignerShortName": "Linux",
    "cveId": "CVE-2026-89571",
    "datePublished": "2026-09-11T19:44:40.328Z",
    "dateReserved": "2026-09-11T19:38:34.726Z",
    "dateUpdated": "2026-09-13T06:31:09.007Z",
    "state": "PUBLISHED"
  },
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  "dataVersion": "5.2",
  "vulnerability-lookup:meta": {
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      "date": "2026-09-15",
      "epss": "0.00124",
      "percentile": "0.02416"
    },
    "nvd": "{\"cve\":{\"id\":\"CVE-2026-89571\",\"sourceIdentifier\":\"416baaa9-dc9f-4396-8d5f-8c081fb06d67\",\"published\":\"2026-09-11T20:19:41.160\",\"lastModified\":\"2026-09-13T07:17:23.097\",\"vulnStatus\":\"Received\",\"cveTags\":[],\"descriptions\":[{\"lang\":\"en\",\"value\":\"In the Linux kernel, the following vulnerability has been resolved:\\n\\ncxl/features: bound fwctl command payload to the input buffer\\n\\nfwctl_cmd_rpc() copies cmd-\u003ein_len bytes into inbuf = kvzalloc(cmd-\u003ein_len)\\nand passes inbuf and in_len to -\u003efw_rpc(). The CXL callback cxlctl_fw_rpc()\\nignores in_len and never checks the user-controlled op_size against it.\\n\\ncxlctl_set_feature() bounds op_size only from below\\n(op_size \u003c= sizeof(feat_in-\u003ehdr)) and then reads op_size - sizeof(hdr)\\nbytes from feat_in-\u003efeat_data via cxl_set_feature(). With a small in_len\\nand a large op_size the first memcpy() already reads past the\\nkvzalloc(in_len) buffer; the out-of-bounds bytes are placed in the mailbox\\npayload and sent to the device, and a large enough op_size can walk into\\nunmapped memory and oops the kernel. The Get paths pin op_size to a fixed\\nsize but likewise read the input struct without checking in_len.\\n\\nReject, at the single dispatch point, any request whose fixed header plus\\nop_size does not fit in the copied-in buffer. The lower-bound test guards\\nthe subtraction and ensures op_size was copied in before it is read.\"}],\"affected\":[{\"source\":\"416baaa9-dc9f-4396-8d5f-8c081fb06d67\",\"affectedData\":[{\"vendor\":\"Linux\",\"product\":\"Linux\",\"defaultStatus\":\"unaffected\",\"programFiles\":[\"drivers/cxl/core/features.c\"],\"repo\":\"https://git.kernel.org/pub/scm/linux/kernel/git/stable/linux.git\",\"versions\":[{\"version\":\"eb5dfcb9e36d0e46089fec777d911313c1876fa3\",\"lessThan\":\"14d52c15d5d99477b20a2d61fe36f347080da6cd\",\"versionType\":\"git\",\"status\":\"affected\"},{\"version\":\"eb5dfcb9e36d0e46089fec777d911313c1876fa3\",\"lessThan\":\"d8957545fe96f7905791c937758ebfc1ae1e5b17\",\"versionType\":\"git\",\"status\":\"affected\"},{\"version\":\"eb5dfcb9e36d0e46089fec777d911313c1876fa3\",\"lessThan\":\"f687394af983df5660b6afae7e0d06969f3af206\",\"versionType\":\"git\",\"status\":\"affected\"}]},{\"vendor\":\"Linux\",\"product\":\"Linux\",\"defaultStatus\":\"affected\",\"programFiles\":[\"drivers/cxl/core/features.c\"],\"repo\":\"https://git.kernel.org/pub/scm/linux/kernel/git/stable/linux.git\",\"versions\":[{\"version\":\"6.15\",\"status\":\"affected\"},{\"version\":\"0\",\"lessThan\":\"6.15\",\"versionType\":\"semver\",\"status\":\"unaffected\"},{\"version\":\"6.18.50\",\"lessThanOrEqual\":\"6.18.*\",\"versionType\":\"semver\",\"status\":\"unaffected\"},{\"version\":\"7.2.4\",\"lessThanOrEqual\":\"7.2.*\",\"versionType\":\"semver\",\"status\":\"unaffected\"},{\"version\":\"7.3-rc1\",\"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:N/A:H\",\"baseScore\":7.1,\"baseSeverity\":\"HIGH\",\"attackVector\":\"LOCAL\",\"attackComplexity\":\"LOW\",\"privilegesRequired\":\"LOW\",\"userInteraction\":\"NONE\",\"scope\":\"UNCHANGED\",\"confidentialityImpact\":\"HIGH\",\"integrityImpact\":\"NONE\",\"availabilityImpact\":\"HIGH\"},\"exploitabilityScore\":1.8,\"impactScore\":5.2}]},\"references\":[{\"url\":\"https://git.kernel.org/stable/c/14d52c15d5d99477b20a2d61fe36f347080da6cd\",\"source\":\"416baaa9-dc9f-4396-8d5f-8c081fb06d67\"},{\"url\":\"https://git.kernel.org/stable/c/d8957545fe96f7905791c937758ebfc1ae1e5b17\",\"source\":\"416baaa9-dc9f-4396-8d5f-8c081fb06d67\"},{\"url\":\"https://git.kernel.org/stable/c/f687394af983df5660b6afae7e0d06969f3af206\",\"source\":\"416baaa9-dc9f-4396-8d5f-8c081fb06d67\"}]}}",
    "redhat_vex": {
      "aggregate_severity": "Moderate",
      "current_release_date": "2026-09-13T06:58:06+00:00",
      "cve": "CVE-2026-89571",
      "id": "CVE-2026-89571",
      "initial_release_date": "2026-09-11T19:44:40.328000+00:00",
      "product_status:known_affected": "2",
      "source": "Red Hat CSAF VEX",
      "status": "final",
      "title": "kernel: Linux kernel: Out-of-bounds read in CXL features leads to denial of service",
      "url": "https://security.access.redhat.com/data/csaf/v2/vex/2026/cve-2026-89571.json",
      "version": "3"
    },
    "suse_vex": {
      "aggregate_severity": "moderate",
      "current_release_date": "2026-09-16T00:01:59Z",
      "cve": "CVE-2026-89571",
      "id": "CVE-2026-89571",
      "initial_release_date": "2026-09-12T16:25:53Z",
      "product_status:known_not_affected": "353",
      "source": "SUSE CSAF VEX",
      "status": "interim",
      "title": "SUSE CVE CVE-2026-89571",
      "url": "https://ftp.suse.com/pub/projects/security/csaf-vex/cve-2026-89571.json",
      "version": "4"
    }
  }
}



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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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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.
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  • 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.


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