# CVE-2026-89630: linux: In the Linux kernel, the following vulnerability has been resolved:  smb: client: restore the data_offset bound in is...

CVE-2026-89630 is fixed in linux on 1 platform by DEBIAN-CVE-2026-89630 (version 7.2.6-1), released September 23, 2026. It is not reported as exploited. Patch Radar priority: Urgent.

- Web page: https://patchblox.com/security/cve/CVE-2026-89630
- Priority: Urgent
- CVSS: 9.1 (critical)
- EPSS: 0.0054
- CISA KEV: not listed
- Exploited (vendor report): no
- Publicly disclosed: no
- Published: Sep 11, 2026

## Description

In the Linux kernel, the following vulnerability has been resolved:  smb: client: restore the data_offset bound in is_valid_oplock_break()  Commit 83bfbd0bb902 ("cifs: Remove the RFC1002 header from smb_hdr") changed the quantity this bound is measured against.  It used to be srv->total_read minus the 4-byte RFC1002 preamble that total_read then included, so it was the SMB message length.  The same commit stopped counting the preamble, and the mechanical substitution to srv->total_read - srv->pdu_size left an expression that is identically zero: standard_receive3() reads MID_HEADER_SIZE() bytes and then exactly pdu_length - MID_HEADER_SIZE() more, adding both to total_read.  len is therefore 0, the subtraction below it wraps, and no __u32 DataOffset can exceed the result, so the check from commit 097f5863b1a0 ("cifs: read overflow in is_valid_oplock_break()") no longer rejects anything.  Use total_read, which is now the message length on its own.

## Where it's fixed

| Platform | Product | Fixed in | Fix | Released |
|---|---|---|---|---|
| Linux | linux Debian 14 | 7.2.6-1 | [DEBIAN-CVE-2026-89630](https://patchblox.com/security/data/fix/linux/debian-cve-2026-89630.md) | Sep 23, 2026 |

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Data as of 2026-11-09T01:18:40Z UTC. Source: Patchblox Patch Radar (https://patchblox.com/security/patch-radar). Patchblox finds out-of-date software on Windows, macOS and Linux and updates it through release rings: https://patchblox.com/demo

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