Kernel-memory disclosure via unchecked SMB2 command offset
Published Aug 16, 2025 · Updated Aug 15, 2026
Out-of-bounds read in Linux ksmbd allows remote authenticated users to disclose kernel memory through a crafted SMB2 write request. ksmbd_smb2_check_message trusts hdr->NextCommand without checking that the compound-command offset remains within the received message, so smb2_write copies bytes beyond the request buffer into an attacker-readable share file. A valid SMB session, a writable share, and an open file handle are required for the 64 KiB disclosure; an oversized read can also panic the kernel.
Summary
What happened
Out-of-bounds read in Linux ksmbd allows remote authenticated users to disclose kernel memory through a crafted SMB2 write request. ksmbd_smb2_check_message trusts hdr->NextCommand without checking that the compound-command offset remains within the received message, so smb2_write copies bytes beyond the request buffer into an attacker-readable share file. A valid SMB session, a writable share, and an open file handle are required for the 64 KiB disclosure; an oversized read can also panic the kernel.
The record
- CVE
- CVE-2023-3865
- Published
- Aug 16, 2025
- Updated
- Aug 15, 2026
- Vendor
- The Linux Kernel Organization
- Product
- Linux
- Classifications
- T1190
- Attack vector
- network
- Privileges
- authenticated
Timeline
How it unfolded
- Aug 16, 2025CVE publishedPublication date reported by the CVE source.
- Aug 15, 2026Record updatedLatest update available in the CVE record.
Exploitability
Present is not the same as exploitable
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Is a vulnerable build present?
Compare these published version ranges with your installed build and any vendor patches.
- Affected versionversion=5.15
- Affected versionversion=e2f34481b24db2fd634b5edb0a5bd0e4d38cc6e9 <3813eee5154d6a4c5875cb4444cb2b63bac8947f
- Affected versionversion=e2f34481b24db2fd634b5edb0a5bd0e4d38cc6e9 <58a9c41064df27632e780c5a3ae3e0e4284957d1
- Affected versionversion=e2f34481b24db2fd634b5edb0a5bd0e4d38cc6e9 <5fe7f7b78290638806211046a99f031ff26164e1
- Affected versionversion=e2f34481b24db2fd634b5edb0a5bd0e4d38cc6e9 <c86211159bc3178b891e0d60e586a32c7b6a231b
What conditions does exploitation require?
What is affected?
Published CVSS scores
CVSS describes severity. EPSS estimates exploitation probability.
Attacks
What attackers are doing with it
Daily unique IPs observed by Shadowserver honeypots for known exploited vulnerabilities (KEVs). Missing observations do not establish an absence of attacks.
Weakness, pattern, technique
Public exploit references
- ZDI-23-980 SMB2 WRITE information-disclosure proof of conceptfunctional · demonstrated
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Technologies
Your stack
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Your stack
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