GCVE Workshop - 22 September 2026 (14:00-18:00), Luxembourg Before The Vulnopticon Conference - Registration

GHSA-2QFV-5W3V-JVFV

Vulnerability from github – Published: 2025-02-27 03:34 – Updated: 2026-07-14 15:31
VLAI
Details

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
Show details on source website
To clipboard 

{
  "affected": [],
  "aliases": [
    "CVE-2025-21731"
  ],
  "database_specific": {
    "cwe_ids": [
      "CWE-416"
    ],
    "github_reviewed": false,
    "github_reviewed_at": null,
    "nvd_published_at": "2025-02-27T02:15:16Z",
    "severity": "HIGH"
  },
  "details": "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.",
  "id": "GHSA-2qfv-5w3v-jvfv",
  "modified": "2026-07-14T15:31:16Z",
  "published": "2025-02-27T03:34:02Z",
  "references": [
    {
      "type": "ADVISORY",
      "url": "https://nvd.nist.gov/vuln/detail/CVE-2025-21731"
    },
    {
      "type": "WEB",
      "url": "https://cert-portal.siemens.com/productcert/html/ssa-019113.html"
    },
    {
      "type": "WEB",
      "url": "https://git.kernel.org/stable/c/6bef6222a3f6c7adb6396f77f25a3579d821b09a"
    },
    {
      "type": "WEB",
      "url": "https://git.kernel.org/stable/c/844b8cdc681612ff24df62cdefddeab5772fadf1"
    },
    {
      "type": "WEB",
      "url": "https://git.kernel.org/stable/c/9793bd5ae4bdbdb2dde401a3cab94a6bfd05e302"
    },
    {
      "type": "WEB",
      "url": "https://git.kernel.org/stable/c/a8ee6ecde2b7bfb58c8a3afe8a9d2b848f580739"
    },
    {
      "type": "WEB",
      "url": "https://git.kernel.org/stable/c/d208d2c52b652913b5eefc8ca434b0d6b757f68f"
    },
    {
      "type": "WEB",
      "url": "https://git.kernel.org/stable/c/e3be8862d73cac833e0fb7602636c19c6cb94b11"
    },
    {
      "type": "WEB",
      "url": "https://git.kernel.org/stable/c/e70a578487a47d7cf058904141e586684d1c3381"
    },
    {
      "type": "WEB",
      "url": "https://git.kernel.org/stable/c/e7343fa33751cb07c1c56b666bf37cfca357130e"
    },
    {
      "type": "WEB",
      "url": "https://lists.debian.org/debian-lts-announce/2025/03/msg00028.html"
    },
    {
      "type": "WEB",
      "url": "https://lists.debian.org/debian-lts-announce/2025/05/msg00030.html"
    }
  ],
  "schema_version": "1.4.0",
  "severity": [
    {
      "score": "CVSS:3.1/AV:L/AC:L/PR:L/UI:N/S:U/C:H/I:H/A:H",
      "type": "CVSS_V3"
    }
  ]
}



Log in or create an account to share your comment.




Tags
Taxonomy of the tags.





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

Author Source Type Date Other

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.


Related by attack behaviour

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.