---
cve: "CVE-2026-80995"
severity: "HIGH"
cvss: 7.8
epss: "0.1%"
vendor: "Linux"
kev: false
exploited: false
published: "2026-09-11 19:42:50"
tags: [cve, security, high]
source: tsecurity.de CVE-Dossier
exported: "2026-09-21T06:06:28+02:00"
---

# CVE-2026-80995

> 7.8 HIGH

## Beschreibung

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

net: mctp: hold a reference to the route device in mctp_route_lookup()

mctp_route_lookup() uses rt->dev without holding a reference on it.
mctp_route_lookup_single() returns the route under RCU only, so the
route's device can be torn down concurrently: mctp_dev_put() drops the
last reference and synchronously kfree()s mdev->addrs.  mctp_dev_saddr()
then reads rt->dev->addrs[0], giving a use-after-free reachable by an
unprivileged local AF_MCTP user on the receive/forwarding path (no
CAP_NET_RAW required):

  BUG: KASAN: slab-use-after-free in mctp_route_lookup
  Read of size 1 at addr ... by task mctp_uaf/...
   mctp_route_lookup
   mctp_pkttype_receive
  Freed by task ...:
   kfree
   mctp_dev_put
   mctp_dev_notify

In the same window mctp_dst_from_route() -> mctp_dev_hold() also
increments a refcount that has already reached zero
("refcount_t: addition on 0 ... mctp_dev_hold").

This reintroduces the use-after-free class of CVE-2023-3439: the source
address lookup was moved ahead of the point where the destination takes
its device reference.

Take a reference with refcount_inc_not_zero() before touching rt->dev,
skip a device that is already dead, and drop the reference once the
destination has taken its own.

## CVSS-Vektor

```
CVSS:3.1/AV:L/AC:L/PR:L/UI:N/S:U/C:H/I:H/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 | Hoch | bad |
| I Integrität | Hoch | bad |
| A Verfügbarkeit | Hoch | bad |

## Patch verfügbar (OSV)

- Kernel ≥ 7.2.4

## Referenzen

- <https://git.kernel.org/stable/c/cc561f8af25586300c2f9d285babb163b866b293>
- <https://git.kernel.org/stable/c/408da1df18116c971c3392e21e50586688cd3fbf>

---
_Exportiert aus dem [tsecurity.de CVE-Dossier](https://tsecurity.de/cve?cve=CVE-2026-80995) · Datenquellen: EUVD (ENISA), NVD, OSV, CISA KEV, FIRST EPSS, Exploit-DB, BSI BITS_