CVE-2026-90067 (GCVE-0-2026-90067)
Vulnerability from cvelistv5
Published
2026-09-17 16:05
Modified
2026-10-19 08:57
Severity ?
7.5 (High) - CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:N/I:N/A:H
Summary
In the Linux kernel, the following vulnerability has been resolved: libceph: validate banner payload length When parsing the Ceph messenger v2 protocol banner, the `payload_len` field is decoded from the banner prefix. If a client sends a banner with a `payload_len` of 0, the kernel sets up a 0-length socket read. This violates an invariant in the state machine, triggering a warning in `populate_in_iter()`: ------------[ cut here ]------------ !iov_iter_count(&con->v2.in_iter) WARNING: net/ceph/messenger_v2.c:3129 at populate_in_iter net/ceph/messenger_v2.c:3129 [inline], CPU#1: kworker/1:3/5070 WARNING: net/ceph/messenger_v2.c:3129 at ceph_con_v2_try_read+0x6634/0x6810 net/ceph/messenger_v2.c:3159, CPU#1: kworker/1:3/5070 ... Call Trace: <TASK> ceph_con_workfn+0x1f5/0x14a0 net/ceph/messenger.c:1575 process_one_work kernel/workqueue.c:3322 [inline] process_scheduled_works+0xa8e/0x14e0 kernel/workqueue.c:3405 worker_thread+0xa47/0xfb0 kernel/workqueue.c:3486 kthread+0x388/0x470 kernel/kthread.c:436 ret_from_fork+0x514/0xb70 arch/x86/kernel/process.c:158 ret_from_fork_asm+0x1a/0x30 arch/x86/entry/entry_64.S:245 </TASK> According to the msgr2 protocol specification, the banner payload is expected to contain at least two 64-bit integers (`server_feat` and `server_req_feat`). Therefore, `payload_len` must be at least 16 bytes. Fix this by adding a check in `process_banner_prefix()` to reject a `payload_len` smaller than 16 bytes. This prevents the 0-length read and correctly aborts the connection with a protocol error.
References
Impacted products
Vendor Product Version
Linux Linux Version: cd1a677cad994021b19665ed476aea63f5d54f31
Version: cd1a677cad994021b19665ed476aea63f5d54f31
Version: cd1a677cad994021b19665ed476aea63f5d54f31
Version: cd1a677cad994021b19665ed476aea63f5d54f31
Version: cd1a677cad994021b19665ed476aea63f5d54f31
Version: cd1a677cad994021b19665ed476aea63f5d54f31
Version: cd1a677cad994021b19665ed476aea63f5d54f31
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{
  "containers": {
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          "product": "Linux",
          "programFiles": [
            "net/ceph/messenger_v2.c"
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      "cpeApplicability": [
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      "descriptions": [
        {
          "lang": "en",
          "value": "In the Linux kernel, the following vulnerability has been resolved:\n\nlibceph: validate banner payload length\n\nWhen parsing the Ceph messenger v2 protocol banner, the `payload_len` field\nis decoded from the banner prefix. If a client sends a banner with a\n`payload_len` of 0, the kernel sets up a 0-length socket read. This\nviolates an invariant in the state machine, triggering a warning in\n`populate_in_iter()`:\n\n------------[ cut here ]------------\n!iov_iter_count(\u0026con-\u003ev2.in_iter)\nWARNING: net/ceph/messenger_v2.c:3129 at populate_in_iter\nnet/ceph/messenger_v2.c:3129 [inline], CPU#1: kworker/1:3/5070\nWARNING: net/ceph/messenger_v2.c:3129 at ceph_con_v2_try_read+0x6634/0x6810\nnet/ceph/messenger_v2.c:3159, CPU#1: kworker/1:3/5070\n...\nCall Trace:\n \u003cTASK\u003e\n ceph_con_workfn+0x1f5/0x14a0 net/ceph/messenger.c:1575\n process_one_work kernel/workqueue.c:3322 [inline]\n process_scheduled_works+0xa8e/0x14e0 kernel/workqueue.c:3405\n worker_thread+0xa47/0xfb0 kernel/workqueue.c:3486\n kthread+0x388/0x470 kernel/kthread.c:436\n ret_from_fork+0x514/0xb70 arch/x86/kernel/process.c:158\n ret_from_fork_asm+0x1a/0x30 arch/x86/entry/entry_64.S:245\n \u003c/TASK\u003e\n\nAccording to the msgr2 protocol specification, the banner payload is\nexpected to contain at least two 64-bit integers (`server_feat` and\n`server_req_feat`). Therefore, `payload_len` must be at least 16 bytes.\n\nFix this by adding a check in `process_banner_prefix()` to reject a\n`payload_len` smaller than 16 bytes. This prevents the 0-length read and\ncorrectly aborts the connection with a protocol error."
        }
      ],
      "metrics": [
        {
          "cvssV3_1": {
            "baseScore": 7.5,
            "baseSeverity": "HIGH",
            "vectorString": "CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:N/I:N/A:H",
            "version": "3.1"
          },
          "scenarios": [
            {
              "lang": "en",
              "value": "AV:N - The attacker-controlled field is the 16-bit payload_len in the msgr2 banner prefix (\"ceph v2\\n\" plus le16) that process_banner_prefix() decodes from bytes received by ceph_con_v2_try_read() on the TCP socket opened by ceph_tcp_connect() in ceph_con_v2_try_write(); a remote MON/OSD/MDS peer sends that banner over routable IP.\nAC:L - The TCP peer fully controls the banner prefix and can set payload_len to 0, so prepare_read_banner_payload() installs a zero-length in_iter and populate_in_iter() hits WARN_ON(!iov_iter_count(\u0026con-\u003ev2.in_iter)) on every such handshake; no race or layout outside the attacker\u2019s control is required.\nPR:N - process_banner_prefix() runs in CEPH_CON_S_V2_BANNER_PREFIX, before prepare_hello() and before CEPH_CON_S_V2_AUTH, so the malformed payload_len is processed prior to Cephx or any other credential check; the attacker is the remote TCP peer and needs no account on the victim host.\nUI:N - Once a kernel CephFS or RBD client is running, __open_session(), reopen_osd(), and MDS ceph_con_open() automatically TCP-reconnect and ceph_con_workfn() reads the peer banner with no further victim action; a compromised cluster daemon triggers the bug on that reconnect.\nS:U - The WARN_ON in populate_in_iter() and the resulting connection fault remain inside the victim kernel\u2019s libceph messenger and do not cross a VM, IOMMU, or sandbox boundary.\nC:N - A zero payload_len only makes populate_in_iter() WARN and return -ENODATA after prepare_read_banner_payload() sets up an empty in_iter; the path does not perform an out-of-bounds read, UAF, or other kernel-memory disclosure.\nI:N - prepare_read_banner_payload() with payload_len 0 never writes past an allocated buffer, and the failure path only faults the connection; attacker input does not corrupt kernel memory or hijack control flow.\nA:H - WARN_ON(!iov_iter_count(\u0026con-\u003ev2.in_iter)) in populate_in_iter() after a zero-length banner payload is an attacker-triggerable kernel warning that panics the host when panic_on_warn is set, and the -ENODATA return through ceph_con_v2_try_read() into con_fault() aborts every msgr2 handshake."
            }
          ]
        }
      ],
      "providerMetadata": {
        "dateUpdated": "2026-10-19T08:57:24.503Z",
        "orgId": "416baaa9-dc9f-4396-8d5f-8c081fb06d67",
        "shortName": "Linux"
      },
      "references": [
        {
          "url": "https://git.kernel.org/stable/c/279c0852999fd2384f4a88155091a99e81f96873"
        },
        {
          "url": "https://git.kernel.org/stable/c/6cf666e47f2b51d5a887ec8a3226cde951757d27"
        },
        {
          "url": "https://git.kernel.org/stable/c/3b2e62a7655d347a845a91155610ddae11daffc6"
        },
        {
          "url": "https://git.kernel.org/stable/c/c1b937ff24b19e69aa7fb1b0f46a74d4c9668692"
        },
        {
          "url": "https://git.kernel.org/stable/c/6d1c6f228854aa89844fd0152d7ed7ac72a55e89"
        },
        {
          "url": "https://git.kernel.org/stable/c/c77633a9595658210a6e216a071e5a396a0835a7"
        },
        {
          "url": "https://git.kernel.org/stable/c/f374967fcdf04001c9b66df1c19106fa83cd91f7"
        }
      ],
      "title": "libceph: validate banner payload length",
      "x_generator": {
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      }
    }
  },
  "cveMetadata": {
    "assignerOrgId": "416baaa9-dc9f-4396-8d5f-8c081fb06d67",
    "assignerShortName": "Linux",
    "cveId": "CVE-2026-90067",
    "datePublished": "2026-09-17T16:05:49.600Z",
    "dateReserved": "2026-09-11T19:38:34.784Z",
    "dateUpdated": "2026-10-19T08:57:24.503Z",
    "state": "PUBLISHED"
  },
  "dataType": "CVE_RECORD",
  "dataVersion": "5.2"
}


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