---
cve: "CVE-2026-31477"
severity: "HIGH"
cvss: 7.5
epss: "48%"
vendor: "Linux"
kev: false
exploited: false
published: "2026-04-22 14:16:44"
tags: [cve, security, high]
source: tsecurity.de CVE-Dossier
exported: "2026-09-12T22:33:27+02:00"
---

# CVE-2026-31477

> 7.5 HIGH

## Beschreibung

In the Linux kernel, the following vulnerability has been resolved:

ksmbd: fix memory leaks and NULL deref in smb2_lock()

smb2_lock() has three error handling issues after list_del() detaches
smb_lock from lock_list at no_check_cl:

1) If vfs_lock_file() returns an unexpected error in the non-UNLOCK
   path, goto out leaks smb_lock and its flock because the out:
   handler only iterates lock_list and rollback_list, neither of
   which contains the detached smb_lock.

2) If vfs_lock_file() returns -ENOENT in the UNLOCK path, goto out
   leaks smb_lock and flock for the same reason.  The error code
   returned to the dispatcher is also stale.

3) In the rollback path, smb_flock_init() can return NULL on
   allocation failure.  The result is dereferenced unconditionally,
   causing a kernel NULL pointer dereference.  Add a NULL check to
   prevent the crash and clean up the bookkeeping; the VFS lock
   itself cannot be rolled back without the allocation and will be
   released at file or connection teardown.

Fix cases 1 and 2 by hoisting the locks_free_lock()/kfree() to before
the if(!rc) check in the UNLOCK branch so all exit paths share one
free site, and by freeing smb_lock and flock before goto out in the
non-UNLOCK branch.  Propagate the correct error code in both cases.
Fix case 3 by wrapping the VFS unlock in an if(rlock) guard and adding
a NULL check for locks_free_lock(rlock) in the shared cleanup.

Found via call-graph analysis using sqry.

## CVSS-Vektor

```
CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:N/I:N/A:H
```

| Metrik | Wert | Bewertung |
|---|---|---|
| AV Angriffsvektor | Netzwerk | bad |
| AC Komplexität | Gering | bad |
| PR Privilegien | Keine | bad |
| UI Interaktion | Keine | bad |
| S Scope | Unverändert | good |
| C Vertraulichkeit | Keine | good |
| I Integrität | Keine | good |
| A Verfügbarkeit | Hoch | bad |

## Patch verfügbar (OSV)

- Kernel ≥ 6.1.168
- Kernel ≥ 6.6.131
- Kernel ≥ 6.12.80
- Kernel ≥ 6.18.21
- Kernel ≥ 6.19.11

## Referenzen

- <https://git.kernel.org/stable/c/cdac6f7e7e428dc70e3b5898ac6999a72ed13993>
- <https://git.kernel.org/stable/c/c9b95ef6f5039f19e46c3a521a4fe1752d91dfe9>
- <https://git.kernel.org/stable/c/91aeaa7256006d79a37298f5a1df23325db91599>
- <https://git.kernel.org/stable/c/3cdacd11b41569ce75b3162142240f2355e04900>
- <https://git.kernel.org/stable/c/aab42f0795620cf0d3955a520f571f697d0f9a2a>
- <https://git.kernel.org/stable/c/309b44ed684496ed3f9c5715d10b899338623512>

---
_Exportiert aus dem [tsecurity.de CVE-Dossier](https://tsecurity.de/cve?cve=CVE-2026-31477) · Datenquellen: EUVD (ENISA), NVD, OSV, CISA KEV, FIRST EPSS, Exploit-DB, BSI BITS_