---
cve: "CVE-2026-31617"
severity: "MEDIUM"
cvss: 5.5
epss: "13%"
vendor: "Linux"
kev: false
exploited: false
published: "2026-04-24 15:16:40"
tags: [cve, security, medium]
source: tsecurity.de CVE-Dossier
exported: "2026-09-08T22:18:14+02:00"
---

# CVE-2026-31617

> 5.5 MEDIUM

## Beschreibung

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

usb: gadget: f_ncm: validate minimum block_len in ncm_unwrap_ntb()

The block_len read from the host-supplied NTB header is checked against
ntb_max but has no lower bound. When block_len is smaller than
opts->ndp_size, the bounds check of:
	ndp_index > (block_len - opts->ndp_size)
will underflow producing a huge unsigned value that ndp_index can never
exceed, defeating the check entirely.

The same underflow occurs in the datagram index checks against block_len
- opts->dpe_size.  With those checks neutered, a malicious USB host can
choose ndp_index and datagram offsets that point past the actual
transfer, and the skb_put_data() copies adjacent kernel memory into the
network skb.

Fix this by rejecting block lengths that cannot hold at least the NTB
header plus one NDP.  This will make block_len - opts->ndp_size and
block_len - opts->dpe_size both well-defined.

Commit 8d2b1a1ec9f5 ("CDC-NCM: avoid overflow in sanity checking") fixed
a related class of issues on the host side of NCM.

## CVSS-Vektor

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

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

## Patch verfügbar (OSV)

- Kernel ≥ 5.10.258
- Kernel ≥ 5.15.209
- Kernel ≥ 6.1.175
- Kernel ≥ 6.6.136
- Kernel ≥ 6.12.83
- Kernel ≥ 6.18.24
- Kernel ≥ 6.19.14
- Kernel ≥ 7.0.1

## Referenzen

- <https://git.kernel.org/stable/c/068a7f2749fff6462a0a908ec415b885fe430f50>
- <https://git.kernel.org/stable/c/1425655c2870054c3ab4712e2b6dbdd331597ada>
- <https://git.kernel.org/stable/c/8b3b7bd3c02f98634baaf36c7fc7ac915f6517ca>
- <https://git.kernel.org/stable/c/0f156bb5334e588034ca68ac2ee92b23f66e56e7>
- <https://git.kernel.org/stable/c/8757a2593631443648218244b9788e193ae0fdc1>
- <https://git.kernel.org/stable/c/6762f8a95772265dd0c2ffe7f400493f3115b135>
- <https://git.kernel.org/stable/c/d58ba8f6546232f8414f396c189297dbee03f1a7>
- <https://git.kernel.org/stable/c/74908b0318d1df1188457040b8714ff4d4b68126>
- <https://git.kernel.org/stable/c/8f993d30b95dc9557a8a96ceca11abed674c8acb>
- <https://access.redhat.com/security/cve/CVE-2026-31617>
- <https://bugzilla.redhat.com/show_bug.cgi?id=2461448>
- <https://security.access.redhat.com/data/csaf/v2/vex/2026/cve-2026-31617.json>

---
_Exportiert aus dem [tsecurity.de CVE-Dossier](https://tsecurity.de/cve?cve=CVE-2026-31617) · Datenquellen: EUVD (ENISA), NVD, OSV, CISA KEV, FIRST EPSS, Exploit-DB, BSI BITS_