Kernel payload misinterpretation via truncated idmap length
Published Sep 24, 2026 · Updated Sep 24, 2026
Integer truncation in the Linux CIFS client causes inconsistent key-payload bounds when an oversized idmap response is accepted. In cifs_idmap_key_instantiate(), prep->datalen can exceed U16_MAX but is assigned to the narrower key->datalen after the full payload is allocated or copied, truncating the recorded length. The condition requires a preparsed cifs.idmap payload larger than 65,535 bytes; later kernel users can interpret the stored payload with bounds that do not match its allocation.
Summary
What happened
Integer truncation in the Linux CIFS client causes inconsistent key-payload bounds when an oversized idmap response is accepted. In cifs_idmap_key_instantiate(), prep->datalen can exceed U16_MAX but is assigned to the narrower key->datalen after the full payload is allocated or copied, truncating the recorded length. The condition requires a preparsed cifs.idmap payload larger than 65,535 bytes; later kernel users can interpret the stored payload with bounds that do not match its allocation.
The record
- CVE
- CVE-2026-93785
- Published
- Sep 24, 2026
- Updated
- Sep 24, 2026
- Vendor
- The Linux Kernel Organization
- Product
- Linux
- Classifications
- Unavailable
- Attack vector
- local
- Privileges
- Unavailable
Timeline
How it unfolded
- Sep 24, 2026CVE publishedPublication date reported by the CVE source.
- Sep 24, 2026Record updatedLatest update available in the CVE record.
Exploitability
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Is a vulnerable build present?
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- Affected versionversion=0 <6.12.111
- Affected versionversion=0 <6.18.53
- Affected versionversion=1da177e4c3f41524e886b7f1b8a0c1fc7321cac2 <455488cd5054bcc59db40fa1cc2c004031a5b2a5
- Affected versionversion=1da177e4c3f41524e886b7f1b8a0c1fc7321cac2 <6cfeef221ac00d63c07f6122f58e6159bde69ca0
- Affected versionversion=1da177e4c3f41524e886b7f1b8a0c1fc7321cac2 <8b12f65d7caf16d124098cb4895a203367d35b57
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What is affected?
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Attacks
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Activity data is delayed. The latest report is Sep 28, 2026.
Weakness, pattern, technique
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Public exploit references
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Technologies
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