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CVE-2025-21731
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.
This record: live connection— last retrieved: 24 September 2026 at 05:13.
Taken directly from NVD, CISA or the vendor — sometimes in English, unchanged from the source.
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.
CVSS:3.1/AV:L/AC:L/PR:L/UI:N/S:U/C:H/I:H/A:H
Attack vector
LOCAL
Privileges required
LOW
User interaction
NONE
Confidentiality
High
Integrity
High
Availability
High
Probability of exploitation within 30 days
0.2%
Percentile
14e
Source: FIRST.org, updated on 23 September 2026.
Limit access to the interactive shell of the additional GNU/Linux subssytem to trusted personnel only.
Our own interpretation and context for the source data above.
IACS Radar assessment
Our own interpretation and context for this vulnerability — not an official source.
IACS Radar priority score
Based on CVSS 7.8, EPSS 0.2%, industrial relevance 55/100.
Combines CVSS, EPSS, KEV status, industrial relevance and exposure relevance — a complement to, not a replacement for, the individual scores below and above.
Conditions for exploitation
Operational impact & energy relevance
Possible loss of visibility of or control over the process upon successful exploitation.
Assessed as relevant to the energy sector based on: Vermeld in een officiële CISA ICS Advisory, wat directe relevantie voor industriële besturingssystemen bevestigt. Vendor "Siemens" is a known supplier of equipment for the energy sector.
Recommended defensive measures
Industrial relevance score
Classification is provisional; manual verification by an OT security analyst is recommended.
Classified by IACS Radar-analysepijplijn (geautomatiseerd) on 24 September 2026.
IEC 62443 mapping
Automatic IACS Radar assessment based on the reported CWE weakness classification; not an official certification statement.