# CVE-2026-90391: lib/test_hmm: fail dmirror_fault() when the mirrored mm is gone

CVE-2026-90391 is fixed in 2 products on 1 platform, first by DEBIAN-CVE-2026-90391, released September 23, 2026. It is not reported as exploited. Patch Radar priority: Routine.

- Web page: https://patchblox.com/security/cve/CVE-2026-90391
- Priority: Routine
- CVSS: 5.5 (Moderate)
- EPSS: 0.0021
- CISA KEV: not listed
- Exploited (vendor report): no
- Publicly disclosed: no
- Published: Sep 17, 2026
- Vendor advisory: https://msrc.microsoft.com/update-guide/vulnerability/CVE-2026-90391

## Description

In the Linux kernel, the following vulnerability has been resolved:  lib/test_hmm: fail dmirror_fault() when the mirrored mm is gone  dmirror_fault() is called from the dmirror_read() and dmirror_write() retry loops after dmirror_do_read() or dmirror_do_write() finds a missing device page table entry.  If the mirrored mm has already exited, mmget_not_zero() fails.  The current code returns 0 in that case, which tells the caller that faulting succeeded even though no page was faulted and no device page table entry was installed.  The caller then retries the same address, hits -ENOENT again, and can loop forever without making progress.  Return -EFAULT instead, so the ioctl fails when the mirrored mm is no longer faultable.

## Where it's fixed

| Platform | Product | Fixed in | Fix | Released |
|---|---|---|---|---|
| Linux | linux Debian 12.15 (bookworm) | 6.1.190-1 | [DEBIAN-CVE-2026-90391](https://patchblox.com/security/data/fix/linux/debian-cve-2026-90391.md) | Sep 23, 2026 |
| Linux | linux Debian 13.5 (trixie) | 6.12.111-1 | [DEBIAN-CVE-2026-90391](https://patchblox.com/security/data/fix/linux/debian-cve-2026-90391.md) | Sep 23, 2026 |
| Linux | linux Debian 14 | 7.2.6-1 | [DEBIAN-CVE-2026-90391](https://patchblox.com/security/data/fix/linux/debian-cve-2026-90391.md) | Sep 23, 2026 |
| Linux | linux-6.12 Debian 12.15 (bookworm) | 6.12.111-1~deb12u1 | [DEBIAN-CVE-2026-90391](https://patchblox.com/security/data/fix/linux/debian-cve-2026-90391.md) | Sep 23, 2026 |

---

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 Patchblox finds out-of-date software on Windows, macOS and Linux and updates it through release rings: https://patchblox.com/demo

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.