CVE-2026-52996
ksmbd: fix durable fd leak on ClientGUID mismatch in durable v2 open
Description
In the Linux kernel, the following vulnerability has been resolved: ksmbd: fix durable fd leak on ClientGUID mismatch in durable v2 open ksmbd_lookup_fd_cguid() returns a ksmbd_file with its refcount incremented via ksmbd_fp_get(). parse_durable_handle_context() in the DURABLE_REQ_V2 case properly releases this reference on every path inside the ClientGUID-match branch, either by calling ksmbd_put_durable_fd() or by transferring ownership to dh_info->fp for a successful reconnect. However, when an entry exists in the global file table with the same CreateGuid but a different ClientGUID, the code simply falls through to the new-open path without dropping the reference obtained from ksmbd_lookup_fd_cguid(). Per MS-SMB2 section 3.3.5.9.10 ("Handling the SMB2_CREATE_DURABLE_HANDLE_REQUEST_V2 Create Context"), the server MUST locate an Open whose Open.CreateGuid matches the request's CreateGuid AND whose Open.ClientGuid matches the ClientGuid of the connection that received the request. If no such Open is found, the server MUST continue with the normal open execution phase. A CreateGuid hit with a ClientGUID mismatch is therefore the "Open not found" case: proceeding with a new open is correct, but the reference obtained purely as a side effect of the lookup must not be leaked. Repeated requests that hit this mismatch pin global_ft entries, prevent __ksmbd_close_fd() from ever running for the corresponding files, and defeat the durable scavenger, leading to long-lived resource leaks. Release the reference in the mismatch path and clear dh_info->fp so subsequent logic does not mistake a non-matching lookup result for a reconnect target.
INFO
Published Date :
June 24, 2026, 5:17 p.m.
Last Modified :
July 15, 2026, 1:04 p.m.
Remotely Exploit :
No
Source :
416baaa9-dc9f-4396-8d5f-8c081fb06d67
CVSS Scores
| Score | Version | Severity | Vector | Exploitability Score | Impact Score | Source |
|---|---|---|---|---|---|---|
| CVSS 3.1 | MEDIUM | [email protected] |
Solution
- Update the Linux kernel to include the ksmbd fix.
- Ensure the fix addresses the durable fd leak.
- Verify ClientGUID matching logic in ksmbd.
- Monitor for resource leaks after applying the update.
References to Advisories, Solutions, and Tools
Here, you will find a curated list of external links that provide in-depth
information, practical solutions, and valuable tools related to
CVE-2026-52996.
CWE - Common Weakness Enumeration
While CVE identifies
specific instances of vulnerabilities, CWE categorizes the common flaws or
weaknesses that can lead to vulnerabilities. CVE-2026-52996 is
associated with the following CWEs:
Common Attack Pattern Enumeration and Classification (CAPEC)
Common Attack Pattern Enumeration and Classification
(CAPEC)
stores attack patterns, which are descriptions of the common attributes and
approaches employed by adversaries to exploit the CVE-2026-52996
weaknesses.
We scan GitHub repositories to detect new proof-of-concept exploits. Following list is a collection of public exploits and proof-of-concepts, which have been published on GitHub (sorted by the most recently updated).
Results are limited to the first 15 repositories due to potential performance issues.
The following list is the news that have been mention
CVE-2026-52996 vulnerability anywhere in the article.
The following table lists the changes that have been made to the
CVE-2026-52996 vulnerability over time.
Vulnerability history details can be useful for understanding the evolution of a vulnerability, and for identifying the most recent changes that may impact the vulnerability's severity, exploitability, or other characteristics.
-
Initial Analysis by [email protected]
Jul. 15, 2026
Action Type Old Value New Value Added CVSS V3.1 AV:L/AC:L/PR:L/UI:N/S:U/C:N/I:N/A:H Added CWE CWE-401 Added CPE Configuration OR *cpe:2.3:o:linux:linux_kernel:*:*:*:*:*:*:*:* versions from (including) 6.13 up to (excluding) 6.18.33 *cpe:2.3:o:linux:linux_kernel:*:*:*:*:*:*:*:* versions from (including) 6.19 up to (excluding) 7.0.10 *cpe:2.3:o:linux:linux_kernel:*:*:*:*:*:*:*:* versions from (including) 6.6.32 up to (excluding) 6.6.141 *cpe:2.3:o:linux:linux_kernel:*:*:*:*:*:*:*:* versions from (including) 6.9 up to (excluding) 6.12.91 Added Reference Type kernel.org: https://git.kernel.org/stable/c/06f709d0e531f3e54d88665dd426be3998a774e6 Types: Patch Added Reference Type kernel.org: https://git.kernel.org/stable/c/407b6e699ba8b45b72cc265eed8a1bc8a7191609 Types: Patch Added Reference Type kernel.org: https://git.kernel.org/stable/c/804054d19886ac6628883d82410f6ee42a818664 Types: Patch Added Reference Type kernel.org: https://git.kernel.org/stable/c/8c4a0ef19c8264c150833131af34541495832cd0 Types: Patch Added Reference Type kernel.org: https://git.kernel.org/stable/c/f31beef633fbf2b5af7805fa187a10bcff1d4b49 Types: Patch -
New CVE Received by 416baaa9-dc9f-4396-8d5f-8c081fb06d67
Jun. 24, 2026
Action Type Old Value New Value Added Affected [{'repo': 'https://git.kernel.org/pub/scm/linux/kernel/git/stable/linux.git', 'vendor': 'Linux', 'product': 'Linux', 'versions': [{'status': 'affected', 'version': '8df4bcdb0a4232192b2445256c39b787d58ef14d', 'lessThan': '407b6e699ba8b45b72cc265eed8a1bc8a7191609', 'versionType': 'git'}, {'status': 'affected', 'version': 'c8efcc786146a951091588e5fa7e3c754850cb3c', 'lessThan': 'f31beef633fbf2b5af7805fa187a10bcff1d4b49', 'versionType': 'git'}, {'status': 'affected', 'version': 'c8efcc786146a951091588e5fa7e3c754850cb3c', 'lessThan': '06f709d0e531f3e54d88665dd426be3998a774e6', 'versionType': 'git'}, {'status': 'affected', 'version': 'c8efcc786146a951091588e5fa7e3c754850cb3c', 'lessThan': '8c4a0ef19c8264c150833131af34541495832cd0', 'versionType': 'git'}, {'status': 'affected', 'version': 'c8efcc786146a951091588e5fa7e3c754850cb3c', 'lessThan': '804054d19886ac6628883d82410f6ee42a818664', 'versionType': 'git'}, {'status': 'affected', 'version': '6.6.32', 'lessThan': '6.6.141', 'versionType': 'semver'}], 'programFiles': ['fs/smb/server/smb2pdu.c'], 'defaultStatus': 'unaffected'}, {'repo': 'https://git.kernel.org/pub/scm/linux/kernel/git/stable/linux.git', 'vendor': 'Linux', 'product': 'Linux', 'versions': [{'status': 'affected', 'version': '6.9'}, {'status': 'unaffected', 'version': '0', 'lessThan': '6.9', 'versionType': 'semver'}, {'status': 'unaffected', 'version': '6.6.141', 'versionType': 'semver', 'lessThanOrEqual': '6.6.*'}, {'status': 'unaffected', 'version': '6.12.91', 'versionType': 'semver', 'lessThanOrEqual': '6.12.*'}, {'status': 'unaffected', 'version': '6.18.33', 'versionType': 'semver', 'lessThanOrEqual': '6.18.*'}, {'status': 'unaffected', 'version': '7.0.10', 'versionType': 'semver', 'lessThanOrEqual': '7.0.*'}, {'status': 'unaffected', 'version': '7.1', 'versionType': 'original_commit_for_fix', 'lessThanOrEqual': '*'}], 'programFiles': ['fs/smb/server/smb2pdu.c'], 'defaultStatus': 'affected'}] Added Description In the Linux kernel, the following vulnerability has been resolved: ksmbd: fix durable fd leak on ClientGUID mismatch in durable v2 open ksmbd_lookup_fd_cguid() returns a ksmbd_file with its refcount incremented via ksmbd_fp_get(). parse_durable_handle_context() in the DURABLE_REQ_V2 case properly releases this reference on every path inside the ClientGUID-match branch, either by calling ksmbd_put_durable_fd() or by transferring ownership to dh_info->fp for a successful reconnect. However, when an entry exists in the global file table with the same CreateGuid but a different ClientGUID, the code simply falls through to the new-open path without dropping the reference obtained from ksmbd_lookup_fd_cguid(). Per MS-SMB2 section 3.3.5.9.10 ("Handling the SMB2_CREATE_DURABLE_HANDLE_REQUEST_V2 Create Context"), the server MUST locate an Open whose Open.CreateGuid matches the request's CreateGuid AND whose Open.ClientGuid matches the ClientGuid of the connection that received the request. If no such Open is found, the server MUST continue with the normal open execution phase. A CreateGuid hit with a ClientGUID mismatch is therefore the "Open not found" case: proceeding with a new open is correct, but the reference obtained purely as a side effect of the lookup must not be leaked. Repeated requests that hit this mismatch pin global_ft entries, prevent __ksmbd_close_fd() from ever running for the corresponding files, and defeat the durable scavenger, leading to long-lived resource leaks. Release the reference in the mismatch path and clear dh_info->fp so subsequent logic does not mistake a non-matching lookup result for a reconnect target. Added Reference https://git.kernel.org/stable/c/06f709d0e531f3e54d88665dd426be3998a774e6 Added Reference https://git.kernel.org/stable/c/407b6e699ba8b45b72cc265eed8a1bc8a7191609 Added Reference https://git.kernel.org/stable/c/804054d19886ac6628883d82410f6ee42a818664 Added Reference https://git.kernel.org/stable/c/8c4a0ef19c8264c150833131af34541495832cd0 Added Reference https://git.kernel.org/stable/c/f31beef633fbf2b5af7805fa187a10bcff1d4b49