# CVE-2026-89678: linux: In the Linux kernel, the following vulnerability has been resolved:  nfsd: fix partial-write detection in nfsd_direct...

CVE-2026-89678 is fixed in linux on 1 platform by DEBIAN-CVE-2026-89678 (version 7.2.6-1), released September 23, 2026. It is not reported as exploited. Patch Radar priority: High.

- Web page: https://patchblox.com/security/cve/CVE-2026-89678
- Priority: High
- CVSS: 7.5 (high)
- EPSS: 0.0038
- 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:  nfsd: fix partial-write detection in nfsd_direct_write  nfsd_direct_write() walks a list of write segments and, after each vfs_iocb_iter_write(), tries to detect a short write so the loop can stop before placing the next segment at a wrong file offset:      host_err = vfs_iocb_iter_write(file, kiocb, &segments[i].iter);     if (host_err < 0)             return host_err;     *cnt += host_err;     if (host_err < segments[i].iter.count)             break;	/* partial write */  vfs_iocb_iter_write() runs the iter through ->write_iter(), which advances the iter by the number of bytes written. By the time the check runs, segments[i].iter.count is the residual, not the original request length:      before write_iter: iter.count == original_len     after  write_iter: iter.count == original_len - host_err  The condition then reduces to host_err < original_len - host_err, so the break fires only when less than half of the segment was written. Any short write completing between 50% and 99% of the segment slips through; the loop advances to the next segment with kiocb->ki_pos only bumped by the short amount, writing the next segment's payload at the wrong offset and over-reporting *cnt to the NFS client.  Snapshot the segment's byte count before the write and compare host_err against that snapshot so any short write breaks the loop.

## Where it's fixed

| Platform | Product | Fixed in | Fix | Released |
|---|---|---|---|---|
| Linux | linux Debian 14 | 7.2.6-1 | [DEBIAN-CVE-2026-89678](https://patchblox.com/security/data/fix/linux/debian-cve-2026-89678.md) | Sep 23, 2026 |

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Data as of 2026-11-08T13:06:02Z 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 Patchblox finds out-of-date software on Windows, macOS and Linux and updates it through release rings: https://patchblox.com/demo

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