# CVE-2026-89642: cifs: call pagecache_isize_extended() in cifs_setsize() when extending

CVE-2026-89642 is fixed in linux on 1 platform, first by DEBIAN-CVE-2026-89642, released September 23, 2026. It is not reported as exploited. Patch Radar priority: Routine.

- Web page: https://patchblox.com/security/cve/CVE-2026-89642
- Priority: Routine
- CVSS: 4.7 (Moderate)
- EPSS: 0.0017
- CISA KEV: not listed
- Exploited (vendor report): no
- Publicly disclosed: no
- Published: Sep 11, 2026
- Vendor advisory: https://msrc.microsoft.com/update-guide/vulnerability/CVE-2026-89642

## Description

In the Linux kernel, the following vulnerability has been resolved:  cifs: call pagecache_isize_extended() in cifs_setsize() when extending  cifs_setsize() calls truncate_pagecache() but skips pagecache_isize_extended() on extension.  truncate_setsize() shows the correct pattern:    i_size_write(inode, newsize);   if (newsize > oldsize)       pagecache_isize_extended(inode, oldsize, newsize);   truncate_pagecache(inode, newsize);  pagecache_isize_extended() zeroes the tail of the page straddling old EOF.  Without it, dirty bytes in that region can be written back to the server, exposing stale data in the newly extended range.

## Where it's fixed

| Platform | Product | Fixed in | Fix | Released |
|---|---|---|---|---|
| Linux | linux Debian 13.5 (trixie) | 6.12.115-2 | [DEBIAN-CVE-2026-89642](https://patchblox.com/security/data/fix/linux/debian-cve-2026-89642.md) | Sep 23, 2026 |
| Linux | linux Debian 14 | 7.2.6-1 | [DEBIAN-CVE-2026-89642](https://patchblox.com/security/data/fix/linux/debian-cve-2026-89642.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 Patchblox finds out-of-date software on Windows, macOS and Linux and updates it through release rings: https://patchblox.com/demo

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