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CVE-2025-21955— ksmbd: prevent connection release during oplock break notification

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存在安全漏洞，该漏洞源于ksmbd在oplock中断通知期间可能释放连接。

CVSS 8.8 · High EPSS 0.50% · P42

Possible ATT&CK Techniques 1 AI

T1068 · Exploitation for Privilege Escalation

Affected Version Matrix 10

VendorProduct Version RangeStatus
Linux Linux 0626e6641f6b467447c81dd7678a69c66f7746cf< 09aeab68033161cb54f194da93e51a11aee6144b affected
0626e6641f6b467447c81dd7678a69c66f7746cf< a4261bbc33fbf99b99c80aa3a2c5097611802980 affected
0626e6641f6b467447c81dd7678a69c66f7746cf< f17d1c63a76b0fe8e9c78023a86507a3a6d62cfa affected
0626e6641f6b467447c81dd7678a69c66f7746cf< 3aa660c059240e0c795217182cf7df32909dd917 affected
5.15 affected
< 5.15 unaffected
6.6.84≤ 6.6.* unaffected
6.12.20≤ 6.12.* unaffected
… +2 more rows
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I. Basic Information for CVE-2025-21955

Vulnerability Information
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Vulnerability Title
ksmbd: prevent connection release during oplock break notification
Source: CVE Program / CVE List V5
Vulnerability Description
In the Linux kernel, the following vulnerability has been resolved: ksmbd: prevent connection release during oplock break notification ksmbd_work could be freed when after connection release. Increment r_count of ksmbd_conn to indicate that requests are not finished yet and to not release the connection.
Source: CVE Program / CVE List V5
CVSS Information
CVSS:3.1/AV:N/AC:L/PR:L/UI:N/S:U/C:H/I:H/A:H
Source: CVE Program / CVE List V5
Vulnerability Type
N/A
Source: CVE Program / CVE List V5
Vulnerability Title
Linux kernel 安全漏洞
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存在安全漏洞，该漏洞源于ksmbd在oplock中断通知期间可能释放连接。
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 0626e6641f6b467447c81dd7678a69c66f7746cf ~ 09aeab68033161cb54f194da93e51a11aee6144b -
Linux Linux 5.15 -

II. Public POCs for CVE-2025-21955

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III. Intelligence Information for CVE-2025-21955

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Patches & Fixes for CVE-2025-21955 (1)

Same Patch Batch · Linux · 2025-04-01 · 93 CVEs total

CVE-2025-21954 9.8 CRITICAL netmem: prevent TX of unreadable skbs
CVE-2025-21927 9.8 CRITICAL nvme-tcp: fix potential memory corruption in nvme_tcp_recv_pdu()
CVE-2025-21946 8.8 HIGH ksmbd: fix out-of-bounds in parse_sec_desc()
CVE-2025-21945 8.8 HIGH ksmbd: fix use-after-free in smb2_lock
CVE-2025-21967 8.8 HIGH ksmbd: fix use-after-free in ksmbd_free_work_struct
CVE-2025-21972 8.8 HIGH net: mctp: unshare packets when reassembling
CVE-2025-21969 8.8 HIGH Bluetooth: L2CAP: Fix slab-use-after-free Read in l2cap_send_cmd
CVE-2025-21947 8.1 HIGH ksmbd: fix type confusion via race condition when using ipc_msg_send_request
CVE-2025-21971 7.8 HIGH net_sched: Prevent creation of classes with TC_H_ROOT
CVE-2025-21949 7.8 HIGH LoongArch: Set hugetlb mmap base address aligned with pmd size
CVE-2025-21899 7.8 HIGH tracing: Fix bad hist from corrupting named_triggers list
CVE-2025-21979 7.8 HIGH wifi: cfg80211: cancel wiphy_work before freeing wiphy
CVE-2025-21901 7.8 HIGH RDMA/bnxt_re: Add sanity checks on rdev validity
CVE-2025-21926 7.8 HIGH net: gso: fix ownership in __udp_gso_segment
CVE-2025-21966 7.8 HIGH dm-flakey: Fix memory corruption in optional corrupt_bio_byte feature
CVE-2025-21970 7.8 HIGH net/mlx5: Bridge, fix the crash caused by LAG state check
CVE-2025-21965 7.8 HIGH sched_ext: Validate prev_cpu in scx_bpf_select_cpu_dfl()
CVE-2025-21934 7.8 HIGH rapidio: fix an API misues when rio_add_net() fails
CVE-2025-21939 7.8 HIGH drm/xe/hmm: Don't dereference struct page pointers without notifier lock
CVE-2025-21958 7.8 HIGH Revert "openvswitch: switch to per-action label counting in conntrack"

Showing top 20 of 93 CVEs. View all on vendor page &rarr; →

IV. Related Vulnerabilities

Same product: Linux
Same vendor: Linux

V. Comments for CVE-2025-21955

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