# CVE-2026-64359: linux: In the Linux kernel, the following vulnerability has been resolved:  nilfs2: reject CLEAN_SEGMENTS ioctl with out-of-...

CVE-2026-64359 is fixed in 2 products on 1 platform, first by DEBIAN-CVE-2026-64359, released July 26, 2026. It is not reported as exploited. Patch Radar priority: Routine.

- Web page: https://patchblox.com/security/cve/CVE-2026-64359
- Priority: Routine
- CVSS: 5.5 (medium)
- EPSS: 0.0012
- CISA KEV: not listed
- Exploited (vendor report): no
- Publicly disclosed: no
- Published: Jul 25, 2026

## Description

In the Linux kernel, the following vulnerability has been resolved:  nilfs2: reject CLEAN_SEGMENTS ioctl with out-of-range segment numbers  Syzbot reported a hung task in nilfs_transaction_begin() where multiple tasks performing chmod() on a nilfs2 mount blocked for over 143 seconds waiting to acquire ns_segctor_sem for read:    INFO: task syz.0.17:5918 blocked for more than 143 seconds.   Call Trace:    schedule+0x164/0x360    rwsem_down_read_slowpath+0x6d9/0x940    down_read+0x99/0x2e0    nilfs_transaction_begin+0x364/0x710 fs/nilfs2/segment.c:221    nilfs_setattr+0x124/0x2c0 fs/nilfs2/inode.c:921    notify_change+0xc1a/0xf40    chmod_common+0x273/0x4a0    do_fchmodat+0x12d/0x230  The writer holding ns_segctor_sem was a concurrent NILFS_IOCTL_CLEAN_SEGMENTS caller, stuck inside printk while emitting per-element warnings from nilfs_sufile_updatev():     __nilfs_msg+0x373/0x450 fs/nilfs2/super.c:78    nilfs_sufile_updatev+0x21c/0x6d0 fs/nilfs2/sufile.c:186    nilfs_sufile_freev fs/nilfs2/sufile.h:93 [inline]    nilfs_free_segments fs/nilfs2/segment.c:1140 [inline]    nilfs_segctor_collect_blocks fs/nilfs2/segment.c:1261 [inline]    nilfs_segctor_do_construct+0x1f55/0x76c0    nilfs_clean_segments+0x3bd/0xa50    nilfs_ioctl_clean_segments fs/nilfs2/ioctl.c:922 [inline]    nilfs_ioctl+0x261f/0x2780  The root cause is that user-supplied segment numbers are not validated before nilfs_clean_segments() begins doing work; the range check on each segnum is performed deep inside the call chain by nilfs_sufile_updatev(), which emits a nilfs_warn() per invalid entry while still holding the segctor lock and the sufile mi_sem.  Under load (repeated invocations across multiple mounts saturating the global printk path), the cumulative printk latency keeps ns_segctor_sem held long enough to trip the hung_task watchdog, blocking concurrent operations such as chmod() that need ns_segctor_sem for read.  Fix by validating the contents of kbufs[4] in nilfs_clean_segments() immediately after acquiring ns_segctor_sem via nilfs_transaction_lock(). Holding ns_segctor_sem serializes the check against nilfs_ioctl_resize(), which can modify ns_nsegments, so the validation uses a consistent value.  Out-of-range segment numbers are rejected with -EINVAL before any segment-cleaning work begins, so the bad entries never reach the per-element diagnostic path inside nilfs_sufile_updatev().

## Where it's fixed

| Platform | Product | Fixed in | Fix | Released |
|---|---|---|---|---|
| Linux | linux Debian 12.15 (bookworm) | 6.1.180-1 | [DEBIAN-CVE-2026-64359](https://patchblox.com/security/data/fix/linux/debian-cve-2026-64359.md) | Jul 26, 2026 |
| Linux | linux Debian 13.5 (trixie) | 6.12.96-1 | [DEBIAN-CVE-2026-64359](https://patchblox.com/security/data/fix/linux/debian-cve-2026-64359.md) | Jul 26, 2026 |
| Linux | linux Debian 14 | 7.1.4-1 | [DEBIAN-CVE-2026-64359](https://patchblox.com/security/data/fix/linux/debian-cve-2026-64359.md) | Jul 26, 2026 |
| Linux | linux-6.12 Debian 12.15 (bookworm) | 6.12.100-1~deb12u1 | [DEBIAN-CVE-2026-64359](https://patchblox.com/security/data/fix/linux/debian-cve-2026-64359.md) | Jul 26, 2026 |

---

Data as of 2026-11-08T06:59:42Z 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

Free to use with attribution: show "Data: Patchblox Patch Radar" with a link to https://patchblox.com/security/patch-radar. Terms, including what needs a written agreement: https://patchblox.com/security/patch-radar/use-the-data

Product names, logos and trademarks shown on Patch Radar belong to their respective owners. They are used only to identify the software each security fix applies to and to help readers find their platform. Their use does not imply any affiliation with, or endorsement by, those owners, and Patchblox is not affiliated with any of them.