# CVE-2021-47395: mac80211: limit injected vht mcs/nss in ieee80211_parse_tx_radiotap

> A missing input validation in the Linux kernel mac80211 module allows attackers to trigger a kernel warning and potential denial of service via crafted radiotap headers.

- **Severity:** Medium 5.5 (`CVSS:3.1/AV:L/AC:L/PR:L/UI:N/S:U/C:N/I:N/A:H`)
- **Exploited in the wild:** Not known
- **Login needed:** Any signed-in user
- **Attackable:** Local or same network only
- **Victim action needed:** Not needed
- **Fix available:** Yes
- **Published:** 21 May 2024
- **Updated:** 11 May 2026
- **Also known as:** DEBIAN-CVE-2021-47395, GHSA-2cf6-4ffg-wwcf, UBUNTU-CVE-2021-47395

## What is CVE-2021-47395?

CVE-2021-47395 is a medium-severity denial of service vulnerability in Linux kernel, published on 21 May 2024. It can only be exploited from the same machine or local network, with no action from the victim.

### Official description

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

mac80211: limit injected vht mcs/nss in ieee80211_parse_tx_radiotap

Limit max values for vht mcs and nss in ieee80211_parse_tx_radiotap
routine in order to fix the following warning reported by syzbot:

WARNING: CPU: 0 PID: 10717 at include/net/mac80211.h:989 ieee80211_rate_set_vht include/net/mac80211.h:989 [inline]
WARNING: CPU: 0 PID: 10717 at include/net/mac80211.h:989 ieee80211_parse_tx_radiotap+0x101e/0x12d0 net/mac80211/tx.c:2244
Modules linked in:
CPU: 0 PID: 10717 Comm: syz-executor.5 Not tainted 5.14.0-syzkaller #0
Hardware name: Google Google Compute Engine/Google Compute Engine, BIOS Google 01/01/2011
RIP: 0010:ieee80211_rate_set_vht include/net/mac80211.h:989 [inline]
RIP: 0010:ieee80211_parse_tx_radiotap+0x101e/0x12d0 net/mac80211/tx.c:2244
RSP: 0018:ffffc9000186f3e8 EFLAGS: 00010216
RAX: 0000000000000618 RBX: ffff88804ef76500 RCX: ffffc900143a5000
RDX: 0000000000040000 RSI: ffffffff888f478e RDI: 0000000000000003
RBP: 00000000ffffffff R08: 0000000000000000 R09: 0000000000000100
R10: ffffffff888f46f9 R11: 0000000000000000 R12: 00000000fffffff8
R13: ffff88804ef7653c R14: 0000000000000001 R15: 0000000000000004
FS:  00007fbf5718f700(0000) GS:ffff8880b9c00000(0000) knlGS:0000000000000000
CS:  0010 DS: 0000 ES: 0000 CR0: 0000000080050033
CR2: 0000001b2de23000 CR3: 000000006a671000 CR4: 00000000001506f0
DR0: 0000000000000000 DR1: 0000000000000000 DR2: 0000000000000000
DR3: 0000000000000000 DR6: 00000000fffe0ff0 DR7: 0000000000000600
Call Trace:
 ieee80211_monitor_select_queue+0xa6/0x250 net/mac80211/iface.c:740
 netdev_core_pick_tx+0x169/0x2e0 net/core/dev.c:4089
 __dev_queue_xmit+0x6f9/0x3710 net/core/dev.c:4165
 __bpf_tx_skb net/core/filter.c:2114 [inline]
 __bpf_redirect_no_mac net/core/filter.c:2139 [inline]
 __bpf_redirect+0x5ba/0xd20 net/core/filter.c:2162
 ____bpf_clone_redirect net/core/filter.c:2429 [inline]
 bpf_clone_redirect+0x2ae/0x420 net/core/filter.c:2401
 bpf_prog_eeb6f53a69e5c6a2+0x59/0x234
 bpf_dispatcher_nop_func include/linux/bpf.h:717 [inline]
 __bpf_prog_run include/linux/filter.h:624 [inline]
 bpf_prog_run include/linux/filter.h:631 [inline]
 bpf_test_run+0x381/0xa30 net/bpf/test_run.c:119
 bpf_prog_test_run_skb+0xb84/0x1ee0 net/bpf/test_run.c:663
 bpf_prog_test_run kernel/bpf/syscall.c:3307 [inline]
 __sys_bpf+0x2137/0x5df0 kernel/bpf/syscall.c:4605
 __do_sys_bpf kernel/bpf/syscall.c:4691 [inline]
 __se_sys_bpf kernel/bpf/syscall.c:4689 [inline]
 __x64_sys_bpf+0x75/0xb0 kernel/bpf/syscall.c:4689
 do_syscall_x64 arch/x86/entry/common.c:50 [inline]
 do_syscall_64+0x35/0xb0 arch/x86/entry/common.c:80
 entry_SYSCALL_64_after_hwframe+0x44/0xae
RIP: 0033:0x4665f9

## Which versions are affected by CVE-2021-47395?

It affects 1 product.


Products: Linux kernel.

## How do I fix CVE-2021-47395?

Apply the vendor's patch.

## Is CVE-2021-47395 being exploited?

There is no known exploitation of CVE-2021-47395 in the wild and no public exploit code.

## Other vulnerabilities in Linux kernel

- [CVE-2026-53266](https://insights.sbomify.com/CVE-2026-53266/): Linux Kernel Out-of-Bounds Write (high 8.8, exploited in the wild)
- [CVE-2013-6282](https://insights.sbomify.com/CVE-2013-6282/): Linux Kernel Improper Input Validation (high 8.8, exploited in the wild)
- [CVE-2022-0185](https://insights.sbomify.com/CVE-2022-0185/): Linux Kernel Heap-Based Buffer Overflow (high 8.4, exploited in the wild)
- [CVE-2013-2094](https://insights.sbomify.com/CVE-2013-2094/): Linux Kernel Privilege Escalation (high 8.4, exploited in the wild)
- [CVE-2026-53362](https://insights.sbomify.com/CVE-2026-53362/): Linux Kernel Unspecified (high 7.8, exploited in the wild)

## Fix prompt for AI coding agents

```text
Check this codebase for CVE-2021-47395 and fix it if it is affected.

What it is: CVE-2021-47395 is a medium-severity denial of service vulnerability in Linux kernel, published on 21 May 2024. It can only be exploited from the same machine or local network, with no action from the victim.
Exploitation: There is no known exploitation of CVE-2021-47395 in the wild and no public exploit code.

Affected product: Linux kernel. No package-level version data is available, so check the vendor advisory linked from the reference page.

Task:
1. Search the dependency manifests and lockfiles (for example package.json, package-lock.json, requirements.txt, poetry.lock, uv.lock, pom.xml, build.gradle, go.mod, Cargo.lock, Gemfile.lock) and any Dockerfiles for the affected packages, including transitive dependencies.
2. If an affected version is in use, upgrade it to the fixed version for its release line with the project's package manager, so the lockfile is regenerated. Prefer the smallest upgrade that fixes it.
3. If there is no fix, or the upgrade would break the build, do not guess: explain the risk and the safest workaround instead.
4. Run the tests and summarise what changed and why.
5. If nothing in the project is affected, say so and change nothing.

Reference: https://insights.sbomify.com/CVE-2021-47395/ (Markdown: https://insights.sbomify.com/CVE-2021-47395/index.md)
```

## Sources

- CVE record: https://www.cve.org/CVERecord?id=CVE-2021-47395
- NVD: https://nvd.nist.gov/vuln/detail/CVE-2021-47395
- OSV: https://osv.dev/vulnerability/CVE-2021-47395

---
From sbomify Insights: https://insights.sbomify.com/CVE-2021-47395/
Summaries are generated and may contain mistakes; the official description above is the record.