CVE-2025-21731 (GCVE-0-2025-21731)

Vulnerability from cvelistv5 – Published: 2025-02-27 02:07 – Updated: 2026-10-15 01:03
VLAI
Title
nbd: don't allow reconnect after disconnect
Summary
In the Linux kernel, the following vulnerability has been resolved: nbd: don't allow reconnect after disconnect Following process can cause nbd_config UAF: 1) grab nbd_config temporarily; 2) nbd_genl_disconnect() flush all recv_work() and release the initial reference: nbd_genl_disconnect nbd_disconnect_and_put nbd_disconnect flush_workqueue(nbd->recv_workq) if (test_and_clear_bit(NBD_RT_HAS_CONFIG_REF, ...)) nbd_config_put -> due to step 1), reference is still not zero 3) nbd_genl_reconfigure() queue recv_work() again; nbd_genl_reconfigure config = nbd_get_config_unlocked(nbd) if (!config) -> succeed if (!test_bit(NBD_RT_BOUND, ...)) -> succeed nbd_reconnect_socket queue_work(nbd->recv_workq, &args->work) 4) step 1) release the reference; 5) Finially, recv_work() will trigger UAF: recv_work nbd_config_put(nbd) -> nbd_config is freed atomic_dec(&config->recv_threads) -> UAF Fix the problem by clearing NBD_RT_BOUND in nbd_genl_disconnect(), so that nbd_genl_reconfigure() will fail.
Severity
7.8 (High)
CVSS:3.1/AV:L/AC:L/PR:L/UI:N/S:U/C:H/I:H/A:H
SSVC
Exploitation: none Automatable: no Technical Impact: total
CISA Coordinator · CISA-ADP (v2.0.3)
Decision recorded 2025-02-27 17:58 UTC
CWE
Assigner
Linux CNA under the mitre root
CNA scorecard D 53/100 over 6653 records in the last 180 days details
References
Impacted products
Vendor Product Version CPE status
Linux Linux Affected: b7aa3d39385dc2d95899f9e379623fef446a2acd , < e70a578487a47d7cf058904141e586684d1c3381 (git)
Affected: b7aa3d39385dc2d95899f9e379623fef446a2acd , < 6bef6222a3f6c7adb6396f77f25a3579d821b09a (git)
Affected: b7aa3d39385dc2d95899f9e379623fef446a2acd , < e3be8862d73cac833e0fb7602636c19c6cb94b11 (git)
Affected: b7aa3d39385dc2d95899f9e379623fef446a2acd , < e7343fa33751cb07c1c56b666bf37cfca357130e (git)
Affected: b7aa3d39385dc2d95899f9e379623fef446a2acd , < d208d2c52b652913b5eefc8ca434b0d6b757f68f (git)
Affected: b7aa3d39385dc2d95899f9e379623fef446a2acd , < a8ee6ecde2b7bfb58c8a3afe8a9d2b848f580739 (git)
Affected: b7aa3d39385dc2d95899f9e379623fef446a2acd , < 9793bd5ae4bdbdb2dde401a3cab94a6bfd05e302 (git)
Affected: b7aa3d39385dc2d95899f9e379623fef446a2acd , < 844b8cdc681612ff24df62cdefddeab5772fadf1 (git)
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Linux Linux Affected: 4.12
Unaffected: 0 , < 4.12 (semver)
Unaffected: 5.4.291 , ≤ 5.4.* (semver)
Unaffected: 5.10.235 , ≤ 5.10.* (semver)
Unaffected: 5.15.179 , ≤ 5.15.* (semver)
Unaffected: 6.1.129 , ≤ 6.1.* (semver)
Unaffected: 6.6.76 , ≤ 6.6.* (semver)
Unaffected: 6.12.13 , ≤ 6.12.* (semver)
Unaffected: 6.13.2 , ≤ 6.13.* (semver)
Unaffected: 6.14 , ≤ * (original_commit_for_fix)
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Siemens SIMATIC S7-1500 CPU 1518-4 PN/DP MFP Affected: V3.1.6 , < * (custom)
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Siemens SIMATIC S7-1500 CPU 1518-4 PN/DP MFP Affected: V3.1.7 , < * (custom)
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Siemens SIMATIC S7-1500 CPU 1518F-4 PN/DP MFP Affected: V3.1.6 , < * (custom)
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Siemens SIMATIC S7-1500 CPU 1518F-4 PN/DP MFP Affected: V3.1.7 , < * (custom)
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Siemens SIMATIC S7-1500 TM MFP - GNU/Linux subsystem Affected: 0 , < * (custom)
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Siemens SIPLUS S7-1500 CPU 1518-4 PN/DP MFP Affected: V3.1.6 , < * (custom)
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Siemens SIPLUS S7-1500 CPU 1518-4 PN/DP MFP Affected: V3.1.7 , < * (custom)
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            "value": "In the Linux kernel, the following vulnerability has been resolved:\n\nnbd: don\u0027t allow reconnect after disconnect\n\nFollowing process can cause nbd_config UAF:\n\n1) grab nbd_config temporarily;\n\n2) nbd_genl_disconnect() flush all recv_work() and release the\ninitial reference:\n\n  nbd_genl_disconnect\n   nbd_disconnect_and_put\n    nbd_disconnect\n     flush_workqueue(nbd-\u003erecv_workq)\n    if (test_and_clear_bit(NBD_RT_HAS_CONFIG_REF, ...))\n     nbd_config_put\n     -\u003e due to step 1), reference is still not zero\n\n3) nbd_genl_reconfigure() queue recv_work() again;\n\n  nbd_genl_reconfigure\n   config = nbd_get_config_unlocked(nbd)\n   if (!config)\n   -\u003e succeed\n   if (!test_bit(NBD_RT_BOUND, ...))\n   -\u003e succeed\n   nbd_reconnect_socket\n    queue_work(nbd-\u003erecv_workq, \u0026args-\u003ework)\n\n4) step 1) release the reference;\n\n5) Finially, recv_work() will trigger UAF:\n\n  recv_work\n   nbd_config_put(nbd)\n   -\u003e nbd_config is freed\n   atomic_dec(\u0026config-\u003erecv_threads)\n   -\u003e UAF\n\nFix the problem by clearing NBD_RT_BOUND in nbd_genl_disconnect(), so\nthat nbd_genl_reconfigure() will fail."
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            "value": "En el kernel de Linux, se ha resuelto la siguiente vulnerabilidad: nbd: no permitir la reconexi\u00f3n despu\u00e9s de la desconexi\u00f3n El siguiente proceso puede causar el nbd_config UAF: 1) grab nbd_config temporarily; 2) nbd_genl_disconnect() flush all recv_work() and release the initial reference: nbd_genl_disconnect nbd_disconnect_and_put nbd_disconnect flush_workqueue(nbd-\u0026gt;recv_workq) if (test_and_clear_bit(NBD_RT_HAS_CONFIG_REF, ...)) nbd_config_put -\u0026gt; due to step 1), reference is still not zero 3) nbd_genl_reconfigure() queue recv_work() again; nbd_genl_reconfigure config = nbd_get_config_unlocked(nbd) if (!config) -\u0026gt; succeed if (!test_bit(NBD_RT_BOUND, ...)) -\u0026gt; succeed nbd_reconnect_socket queue_work(nbd-\u0026gt;recv_workq, \u0026amp;args-\u0026gt;work) 4) step 1) release the reference; 5) Finially, recv_work() will trigger UAF: recv_work nbd_config_put(nbd) -\u0026gt; nbd_config is freed atomic_dec(\u0026amp;config-\u0026gt;recv_threads) -\u0026gt; UAF Fix the problem by clearing NBD_RT_BOUND in nbd_genl_disconnect(), so that nbd_genl_reconfigure() will fail. "
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                  "lessThan": "6bef6222a3f6c7adb6396f77f25a3579d821b09a",
                  "status": "affected",
                  "version": "b7aa3d39385dc2d95899f9e379623fef446a2acd",
                  "versionType": "git"
                },
                {
                  "lessThan": "e3be8862d73cac833e0fb7602636c19c6cb94b11",
                  "status": "affected",
                  "version": "b7aa3d39385dc2d95899f9e379623fef446a2acd",
                  "versionType": "git"
                },
                {
                  "lessThan": "e7343fa33751cb07c1c56b666bf37cfca357130e",
                  "status": "affected",
                  "version": "b7aa3d39385dc2d95899f9e379623fef446a2acd",
                  "versionType": "git"
                },
                {
                  "lessThan": "d208d2c52b652913b5eefc8ca434b0d6b757f68f",
                  "status": "affected",
                  "version": "b7aa3d39385dc2d95899f9e379623fef446a2acd",
                  "versionType": "git"
                },
                {
                  "lessThan": "a8ee6ecde2b7bfb58c8a3afe8a9d2b848f580739",
                  "status": "affected",
                  "version": "b7aa3d39385dc2d95899f9e379623fef446a2acd",
                  "versionType": "git"
                },
                {
                  "lessThan": "9793bd5ae4bdbdb2dde401a3cab94a6bfd05e302",
                  "status": "affected",
                  "version": "b7aa3d39385dc2d95899f9e379623fef446a2acd",
                  "versionType": "git"
                },
                {
                  "lessThan": "844b8cdc681612ff24df62cdefddeab5772fadf1",
                  "status": "affected",
                  "version": "b7aa3d39385dc2d95899f9e379623fef446a2acd",
                  "versionType": "git"
                }
              ]
            },
            {
              "defaultStatus": "affected",
              "product": "Linux",
              "programFiles": [
                "drivers/block/nbd.c"
              ],
              "repo": "https://git.kernel.org/pub/scm/linux/kernel/git/stable/linux.git",
              "vendor": "Linux",
              "versions": [
                {
                  "status": "affected",
                  "version": "4.12"
                },
                {
                  "lessThan": "4.12",
                  "status": "unaffected",
                  "version": "0",
                  "versionType": "semver"
                },
                {
                  "lessThanOrEqual": "5.4.*",
                  "status": "unaffected",
                  "version": "5.4.291",
                  "versionType": "semver"
                },
                {
                  "lessThanOrEqual": "5.10.*",
                  "status": "unaffected",
                  "version": "5.10.235",
                  "versionType": "semver"
                },
                {
                  "lessThanOrEqual": "5.15.*",
                  "status": "unaffected",
                  "version": "5.15.179",
                  "versionType": "semver"
                },
                {
                  "lessThanOrEqual": "6.1.*",
                  "status": "unaffected",
                  "version": "6.1.129",
                  "versionType": "semver"
                },
                {
                  "lessThanOrEqual": "6.6.*",
                  "status": "unaffected",
                  "version": "6.6.76",
                  "versionType": "semver"
                },
                {
                  "lessThanOrEqual": "6.12.*",
                  "status": "unaffected",
                  "version": "6.12.13",
                  "versionType": "semver"
                },
                {
                  "lessThanOrEqual": "6.13.*",
                  "status": "unaffected",
                  "version": "6.13.2",
                  "versionType": "semver"
                },
                {
                  "lessThanOrEqual": "*",
                  "status": "unaffected",
                  "version": "6.14",
                  "versionType": "original_commit_for_fix"
                }
              ]
            }
          ],
          "cpeApplicability": [
            {
              "nodes": [
                {
                  "cpeMatch": [
                    {
                      "criteria": "cpe:2.3:o:linux:linux_kernel:*:*:*:*:*:*:*:*",
                      "versionEndExcluding": "5.4.291",
                      "versionStartIncluding": "4.12",
                      "vulnerable": true
                    },
                    {
                      "criteria": "cpe:2.3:o:linux:linux_kernel:*:*:*:*:*:*:*:*",
                      "versionEndExcluding": "5.10.235",
                      "versionStartIncluding": "4.12",
                      "vulnerable": true
                    },
                    {
                      "criteria": "cpe:2.3:o:linux:linux_kernel:*:*:*:*:*:*:*:*",
                      "versionEndExcluding": "5.15.179",
                      "versionStartIncluding": "4.12",
                      "vulnerable": true
                    },
                    {
                      "criteria": "cpe:2.3:o:linux:linux_kernel:*:*:*:*:*:*:*:*",
                      "versionEndExcluding": "6.1.129",
                      "versionStartIncluding": "4.12",
                      "vulnerable": true
                    },
                    {
                      "criteria": "cpe:2.3:o:linux:linux_kernel:*:*:*:*:*:*:*:*",
                      "versionEndExcluding": "6.6.76",
                      "versionStartIncluding": "4.12",
                      "vulnerable": true
                    },
                    {
                      "criteria": "cpe:2.3:o:linux:linux_kernel:*:*:*:*:*:*:*:*",
                      "versionEndExcluding": "6.12.13",
                      "versionStartIncluding": "4.12",
                      "vulnerable": true
                    },
                    {
                      "criteria": "cpe:2.3:o:linux:linux_kernel:*:*:*:*:*:*:*:*",
                      "versionEndExcluding": "6.13.2",
                      "versionStartIncluding": "4.12",
                      "vulnerable": true
                    },
                    {
                      "criteria": "cpe:2.3:o:linux:linux_kernel:*:*:*:*:*:*:*:*",
                      "versionEndExcluding": "6.14",
                      "versionStartIncluding": "4.12",
                      "vulnerable": true
                    }
                  ],
                  "negate": false,
                  "operator": "OR"
                }
              ]
            }
          ],
          "descriptions": [
            {
              "lang": "en",
              "value": "In the Linux kernel, the following vulnerability has been resolved:\n\nnbd: don\u0027t allow reconnect after disconnect\n\nFollowing process can cause nbd_config UAF:\n\n1) grab nbd_config temporarily;\n\n2) nbd_genl_disconnect() flush all recv_work() and release the\ninitial reference:\n\n  nbd_genl_disconnect\n   nbd_disconnect_and_put\n    nbd_disconnect\n     flush_workqueue(nbd-\u003erecv_workq)\n    if (test_and_clear_bit(NBD_RT_HAS_CONFIG_REF, ...))\n     nbd_config_put\n     -\u003e due to step 1), reference is still not zero\n\n3) nbd_genl_reconfigure() queue recv_work() again;\n\n  nbd_genl_reconfigure\n   config = nbd_get_config_unlocked(nbd)\n   if (!config)\n   -\u003e succeed\n   if (!test_bit(NBD_RT_BOUND, ...))\n   -\u003e succeed\n   nbd_reconnect_socket\n    queue_work(nbd-\u003erecv_workq, \u0026args-\u003ework)\n\n4) step 1) release the reference;\n\n5) Finially, recv_work() will trigger UAF:\n\n  recv_work\n   nbd_config_put(nbd)\n   -\u003e nbd_config is freed\n   atomic_dec(\u0026config-\u003erecv_threads)\n   -\u003e UAF\n\nFix the problem by clearing NBD_RT_BOUND in nbd_genl_disconnect(), so\nthat nbd_genl_reconfigure() will fail."
            }
          ],
          "providerMetadata": {
            "dateUpdated": "2026-05-11T21:05:20.600Z",
            "orgId": "416baaa9-dc9f-4396-8d5f-8c081fb06d67",
            "shortName": "Linux"
          },
          "references": [
            {
              "url": "https://git.kernel.org/stable/c/e70a578487a47d7cf058904141e586684d1c3381"
            },
            {
              "url": "https://git.kernel.org/stable/c/6bef6222a3f6c7adb6396f77f25a3579d821b09a"
            },
            {
              "url": "https://git.kernel.org/stable/c/e3be8862d73cac833e0fb7602636c19c6cb94b11"
            },
            {
              "url": "https://git.kernel.org/stable/c/e7343fa33751cb07c1c56b666bf37cfca357130e"
            },
            {
              "url": "https://git.kernel.org/stable/c/d208d2c52b652913b5eefc8ca434b0d6b757f68f"
            },
            {
              "url": "https://git.kernel.org/stable/c/a8ee6ecde2b7bfb58c8a3afe8a9d2b848f580739"
            },
            {
              "url": "https://git.kernel.org/stable/c/9793bd5ae4bdbdb2dde401a3cab94a6bfd05e302"
            },
            {
              "url": "https://git.kernel.org/stable/c/844b8cdc681612ff24df62cdefddeab5772fadf1"
            }
          ],
          "title": "nbd: don\u0027t allow reconnect after disconnect",
          "x_generator": {
            "engine": "bippy-1.2.0"
          }
        }
      },
      "cveMetadata": {
        "assignerOrgId": "416baaa9-dc9f-4396-8d5f-8c081fb06d67",
        "assignerShortName": "Linux",
        "cveId": "CVE-2025-21731",
        "datePublished": "2025-02-27T02:07:35.927Z",
        "dateReserved": "2024-12-29T08:45:45.755Z",
        "dateUpdated": "2026-09-08T08:40:26.587Z",
        "state": "PUBLISHED"
      },
      "dataType": "CVE_RECORD",
      "dataVersion": "5.2"
    }
  }
}



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Sightings

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Nomenclature

  • Seen: The vulnerability was mentioned, discussed, or observed by the user.
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  • Published Proof of Concept: A public proof of concept is available for this vulnerability.
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Vulnerability timeline

Sightings and recorded dates, grouped by day · UTC

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Following the VTEM framework (Black Hat USA 2015), time to patch starts when the vendor or a coordinator was informed, total time to patch at discovery, and disclosure to patch at public disclosure; vendor response time runs from the report to its acknowledgement. Time to exploit and time unpatched start at the earliest discovery or report, falling back to public disclosure. Unpatched time ends at the first recorded patch, or the calculation time when no patch is recorded. Exploitation to patch shows the interval between those two events; a published proof of concept is a public exploit, not exploitation.

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    Vulnerabilities whose description is nearest to this one in the vector space of the CIRCL/vulnerability-attack-technique-biencoder model. This is a similarity search over the bi-encoder space (plain cosine), not a classification, and it has no measured accuracy.