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.
Advisories
Source ID Title
Debian DLA Debian DLA DLA-4102-1 linux-6.1 security update
Debian DLA Debian DLA DLA-4178-1 linux security update
EUVD EUVD EUVD-2025-5235 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.
Ubuntu USN Ubuntu USN USN-7510-1 Linux kernel vulnerabilities
Ubuntu USN Ubuntu USN USN-7510-2 Linux kernel (FIPS) vulnerabilities
Ubuntu USN Ubuntu USN USN-7510-3 Linux kernel vulnerabilities
Ubuntu USN Ubuntu USN USN-7510-4 Linux kernel (Real-time) vulnerabilities
Ubuntu USN Ubuntu USN USN-7510-5 Linux kernel (Azure FIPS) vulnerabilities
Ubuntu USN Ubuntu USN USN-7510-6 Linux kernel (AWS FIPS) vulnerabilities
Ubuntu USN Ubuntu USN USN-7510-7 Linux kernel vulnerabilities
Ubuntu USN Ubuntu USN USN-7510-8 Linux kernel (AWS) vulnerabilities
Ubuntu USN Ubuntu USN USN-7511-1 Linux kernel (GCP) vulnerabilities
Ubuntu USN Ubuntu USN USN-7511-2 Linux kernel (GCP FIPS) vulnerabilities
Ubuntu USN Ubuntu USN USN-7511-3 Linux kernel (GKE) vulnerabilities
Ubuntu USN Ubuntu USN USN-7512-1 Linux kernel (GCP) vulnerabilities
Ubuntu USN Ubuntu USN USN-7516-1 Linux kernel vulnerabilities
Ubuntu USN Ubuntu USN USN-7516-2 Linux kernel (GCP FIPS) vulnerabilities
Ubuntu USN Ubuntu USN USN-7516-3 Linux kernel vulnerabilities
Ubuntu USN Ubuntu USN USN-7516-4 Linux kernel (Oracle) vulnerabilities
Ubuntu USN Ubuntu USN USN-7516-5 Linux kernel (HWE) vulnerabilities
Ubuntu USN Ubuntu USN USN-7516-6 Linux kernel (IBM) vulnerabilities
Ubuntu USN Ubuntu USN USN-7516-7 Linux kernel (AWS) vulnerabilities
Ubuntu USN Ubuntu USN USN-7516-8 Linux kernel (FIPS) vulnerabilities
Ubuntu USN Ubuntu USN USN-7516-9 Linux kernel (AWS) vulnerabilities
Ubuntu USN Ubuntu USN USN-7517-1 Linux kernel (Xilinx ZynqMP) vulnerabilities
Ubuntu USN Ubuntu USN USN-7517-2 Linux kernel (IBM) vulnerabilities
Ubuntu USN Ubuntu USN USN-7517-3 Linux kernel (BlueField) vulnerabilities
Ubuntu USN Ubuntu USN USN-7518-1 Linux kernel (Azure FIPS) vulnerabilities
Ubuntu USN Ubuntu USN USN-7521-1 Linux kernel vulnerabilities
Ubuntu USN Ubuntu USN USN-7521-2 Linux kernel (AWS) vulnerabilities
Ubuntu USN Ubuntu USN USN-7521-3 Linux kernel vulnerabilities
Ubuntu USN Ubuntu USN USN-7539-1 Linux kernel (Raspberry Pi) vulnerabilities
Ubuntu USN Ubuntu USN USN-7540-1 Linux kernel (Raspberry Pi) vulnerabilities
Ubuntu USN Ubuntu USN USN-7593-1 Linux kernel (HWE) vulnerabilities
Ubuntu USN Ubuntu USN USN-7602-1 Linux kernel (Xilinx ZynqMP) vulnerabilities
Ubuntu USN Ubuntu USN USN-7640-1 Linux kernel (IoT) vulnerabilities
Ubuntu USN Ubuntu USN USN-7651-1 Linux kernel vulnerabilities
Ubuntu USN Ubuntu USN USN-7651-2 Linux kernel vulnerabilities
Ubuntu USN Ubuntu USN USN-7651-3 Linux kernel vulnerabilities
Ubuntu USN Ubuntu USN USN-7651-4 Linux kernel (GCP) vulnerabilities
Ubuntu USN Ubuntu USN USN-7651-5 Linux kernel (Raspberry Pi Real-time) vulnerabilities
Ubuntu USN Ubuntu USN USN-7651-6 Linux kernel (Raspberry Pi) vulnerabilities
Ubuntu USN Ubuntu USN USN-7652-1 Linux kernel (Real-time) vulnerabilities
Ubuntu USN Ubuntu USN USN-7653-1 Linux kernel (HWE) vulnerabilities
Ubuntu USN Ubuntu USN USN-7737-1 Linux kernel (Azure) vulnerabilities
Fixes

Solution

No solution given by the vendor.


Workaround

No workaround given by the vendor.

History

Mon, 03 Nov 2025 20:30:00 +0000


Mon, 24 Mar 2025 19:15:00 +0000

Type Values Removed Values Added
First Time appeared Linux
Linux linux Kernel
CPEs cpe:2.3:o:linux:linux_kernel:*:*:*:*:*:*:*:*
Vendors & Products Linux
Linux linux Kernel

Thu, 13 Mar 2025 12:30:00 +0000


Tue, 04 Mar 2025 03:45:00 +0000

Type Values Removed Values Added
Metrics ssvc

{'options': {'Automatable': 'no', 'Exploitation': 'none', 'Technical Impact': 'total'}, 'version': '2.0.3'}


Fri, 28 Feb 2025 02:00:00 +0000


Thu, 27 Feb 2025 18:45:00 +0000

Type Values Removed Values Added
Weaknesses CWE-416
Metrics cvssV3_1

{'score': 7.8, 'vector': 'CVSS:3.1/AV:L/AC:L/PR:L/UI:N/S:U/C:H/I:H/A:H'}


Thu, 27 Feb 2025 02:15:00 +0000

Type Values Removed Values Added
Description 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.
Title nbd: don't allow reconnect after disconnect
References

cve-icon MITRE

Status: PUBLISHED

Assigner: Linux

Published:

Updated: 2025-11-03T19:36:36.130Z

Reserved: 2024-12-29T08:45:45.755Z

Link: CVE-2025-21731

cve-icon Vulnrichment

Updated: 2025-02-27T17:58:02.900Z

cve-icon NVD

Status : Modified

Published: 2025-02-27T02:15:16.833

Modified: 2025-11-03T20:17:13.173

Link: CVE-2025-21731

cve-icon Redhat

Severity : Moderate

Publid Date: 2025-02-27T00:00:00Z

Links: CVE-2025-21731 - Bugzilla

cve-icon OpenCVE Enrichment

No data.