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CVE-2025-21731— nbd: don't allow reconnect after disconnect

Quick assessment

Affected
Linux Linux
Exploitation
No confirmed in-the-wild exploitation; assess based on exposure
Recommended action
Check the vendor advisory and references for a fixed version. If immediate upgrade is impossible, restrict exposure and increase monitoring.

Linux kernel是美国Linux基金会的开源操作系统Linux所使用的内核。 Linux kernel存在资源管理错误漏洞，该漏洞源于nbd在断开连接后允许重新连接，可能导致释放后重用。

AI Predicted 7.8 Difficulty: Hard EPSS 0.24% · P14

Possible ATT&CK Techniques 1 AI

T1190 · Exploit Public-Facing Application

Affected Version Matrix 18

VendorProduct Version RangeStatus
Linux Linux b7aa3d39385dc2d95899f9e379623fef446a2acd< e70a578487a47d7cf058904141e586684d1c3381 affected
b7aa3d39385dc2d95899f9e379623fef446a2acd< 6bef6222a3f6c7adb6396f77f25a3579d821b09a affected
b7aa3d39385dc2d95899f9e379623fef446a2acd< e3be8862d73cac833e0fb7602636c19c6cb94b11 affected
b7aa3d39385dc2d95899f9e379623fef446a2acd< e7343fa33751cb07c1c56b666bf37cfca357130e affected
b7aa3d39385dc2d95899f9e379623fef446a2acd< d208d2c52b652913b5eefc8ca434b0d6b757f68f affected
b7aa3d39385dc2d95899f9e379623fef446a2acd< a8ee6ecde2b7bfb58c8a3afe8a9d2b848f580739 affected
b7aa3d39385dc2d95899f9e379623fef446a2acd< 9793bd5ae4bdbdb2dde401a3cab94a6bfd05e302 affected
b7aa3d39385dc2d95899f9e379623fef446a2acd< 844b8cdc681612ff24df62cdefddeab5772fadf1 affected
… +10 more rows
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I. Basic Information for CVE-2025-21731

Vulnerability Information
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Vulnerability Title
nbd: don't allow reconnect after disconnect
Source: CVE Program / CVE List V5
Vulnerability 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.
Source: CVE Program / CVE List V5
CVSS Information
N/A
Source: CVE Program / CVE List V5
Vulnerability Type
N/A
Source: CVE Program / CVE List V5
Vulnerability Title
Linux kernel 资源管理错误漏洞
Source: CNNVD (China National Vulnerability Database)
Vulnerability Description
Linux kernel是美国Linux基金会的开源操作系统Linux所使用的内核。 Linux kernel存在资源管理错误漏洞，该漏洞源于nbd在断开连接后允许重新连接，可能导致释放后重用。
Source: CNNVD (China National Vulnerability Database)
CVSS Information
N/A
Source: CNNVD (China National Vulnerability Database)
Vulnerability Type
N/A
Source: CNNVD (China National Vulnerability Database)

Affected Products

Vendor Product Affected Versions CPE Subscribe
Linux Linux b7aa3d39385dc2d95899f9e379623fef446a2acd ~ e70a578487a47d7cf058904141e586684d1c3381 -
Linux Linux 4.12 -

II. Public POCs for CVE-2025-21731

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III. Intelligence Information for CVE-2025-21731

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Patches & Fixes for CVE-2025-21731 (5)

Other References for CVE-2025-21731 (3)

Same Patch Batch · Linux · 2025-02-27 · 177 CVEs total

CVE-2025-21796 9.8 CRITICAL nfsd: clear acl_access/acl_default after releasing them
CVE-2025-21805 9.8 CRITICAL RDMA/rtrs: Add missing deinit() call
CVE-2025-21707 9.8 CRITICAL mptcp: consolidate suboption status
CVE-2025-21748 9.8 CRITICAL ksmbd: fix integer overflows on 32 bit systems
CVE-2024-58006 9.6 CRITICAL PCI: dwc: ep: Prevent changing BAR size/flags in pci_epc_set_bar()
CVE-2025-21735 8.8 HIGH NFC: nci: Add bounds checking in nci_hci_create_pipe()
CVE-2024-57999 8.8 HIGH powerpc/pseries/iommu: IOMMU incorrectly marks MMIO range in DDW
CVE-2024-57997 8.8 HIGH wifi: wcn36xx: fix channel survey memory allocation size
CVE-2024-57995 8.8 HIGH wifi: ath12k: fix read pointer after free in ath12k_mac_assign_vif_to_vdev()
CVE-2025-21710 8.2 HIGH tcp: correct handling of extreme memory squeeze
CVE-2024-57973 8.1 HIGH rdma/cxgb4: Prevent potential integer overflow on 32bit
CVE-2025-21760 8.1 HIGH ndisc: extend RCU protection in ndisc_send_skb()
CVE-2025-21766 8.1 HIGH ipv4: use RCU protection in __ip_rt_update_pmtu()
CVE-2025-21765 8.1 HIGH ipv6: use RCU protection in ip6_default_advmss()
CVE-2025-21762 8.1 HIGH arp: use RCU protection in arp_xmit()
CVE-2025-21730 7.8 HIGH wifi: rtw89: avoid to init mgnt_entry list twice when WoWLAN failed
CVE-2025-21729 7.8 HIGH wifi: rtw89: fix race between cancel_hw_scan and hw_scan completion
CVE-2025-21772 7.8 HIGH partitions: mac: fix handling of bogus partition table
CVE-2024-58002 7.8 HIGH media: uvcvideo: Remove dangling pointers
CVE-2024-52560 7.8 HIGH fs/ntfs3: Mark inode as bad as soon as error detected in mi_enum_attr()

Showing top 20 of 177 CVEs. View all on vendor page &rarr; →

IV. Related Vulnerabilities

Same product: Linux
Same vendor: Linux