---
cve: "CVE-2021-47013"
severity: "CRITICAL"
cvss: 9.8
epss: "78%"
vendor: "Linux"
kev: false
exploited: false
published: "2024-02-28 09:15:38"
tags: [cve, security, critical]
source: tsecurity.de CVE-Dossier
exported: "2026-09-10T18:58:09+02:00"
---

# CVE-2021-47013

> 9.8 CRITICAL

## Beschreibung

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

net:emac/emac-mac: Fix a use after free in emac_mac_tx_buf_send

In emac_mac_tx_buf_send, it calls emac_tx_fill_tpd(..,skb,..).
If some error happens in emac_tx_fill_tpd(), the skb will be freed via
dev_kfree_skb(skb) in error branch of emac_tx_fill_tpd().
But the freed skb is still used via skb->len by netdev_sent_queue(,skb->len).

As i observed that emac_tx_fill_tpd() haven't modified the value of skb->len,
thus my patch assigns skb->len to 'len' before the possible free and
use 'len' instead of skb->len later.

## CVSS-Vektor

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

## Referenzen

- <https://git.kernel.org/stable/c/c7f75d11fe72913d2619f97b2334b083cd7bb955>
- <https://git.kernel.org/stable/c/dc1b438a35773d030be0ee80d9c635c3e558a322>
- <https://git.kernel.org/stable/c/16d8c44be52e3650917736d45f5904384a9da834>
- <https://git.kernel.org/stable/c/55fcdd1258faaecca74b91b88cc0921f9edd775d>
- <https://git.kernel.org/stable/c/9dc373f74097edd0e35f3393d6248eda8d1ba99d>
- <https://git.kernel.org/stable/c/8c06f34785068b87e2b560534c77c163d6c6dca7>
- <https://git.kernel.org/stable/c/e407495ba6788a67d1bd41714158c079e340879b>
- <https://git.kernel.org/stable/c/6d72e7c767acbbdd44ebc7d89c6690b405b32b57>

---
_Exportiert aus dem [tsecurity.de CVE-Dossier](https://tsecurity.de/cve?cve=CVE-2021-47013) · Datenquellen: EUVD (ENISA), NVD, OSV, CISA KEV, FIRST EPSS, Exploit-DB, BSI BITS_