# CVE-2021-47633: ath5k: fix OOB in ath5k_eeprom_read_pcal_info_5111

> An out-of-bounds write in the ath5k wireless driver allows attackers to cause memory corruption, potentially leading to code execution or system crashes.

- **Severity:** High 7.1 (`CVSS:3.1/AV:L/AC:L/PR:L/UI:N/S:U/C:H/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:** 26 Feb 2025
- **Updated:** 11 May 2026
- **Also known as:** DEBIAN-CVE-2021-47633, GHSA-hh39-hp2x-qgp5, UBUNTU-CVE-2021-47633

## What is CVE-2021-47633?

CVE-2021-47633 is a high-severity memory corruption vulnerability in Linux kernel, published on 26 Feb 2025. 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:

ath5k: fix OOB in ath5k_eeprom_read_pcal_info_5111

The bug was found during fuzzing. Stacktrace locates it in
ath5k_eeprom_convert_pcal_info_5111.
When none of the curve is selected in the loop, idx can go
up to AR5K_EEPROM_N_PD_CURVES. The line makes pd out of bound.
pd = &chinfo[pier].pd_curves[idx];

There are many OOB writes using pd later in the code. So I
added a sanity check for idx. Checks for other loops involving
AR5K_EEPROM_N_PD_CURVES are not needed as the loop index is not
used outside the loops.

The patch is NOT tested with real device.

The following is the fuzzing report

BUG: KASAN: slab-out-of-bounds in ath5k_eeprom_read_pcal_info_5111+0x126a/0x1390 [ath5k]
Write of size 1 at addr ffff8880174a4d60 by task modprobe/214

CPU: 0 PID: 214 Comm: modprobe Not tainted 5.6.0 #1
Call Trace:
 dump_stack+0x76/0xa0
 print_address_description.constprop.0+0x16/0x200
 ? ath5k_eeprom_read_pcal_info_5111+0x126a/0x1390 [ath5k]
 ? ath5k_eeprom_read_pcal_info_5111+0x126a/0x1390 [ath5k]
 __kasan_report.cold+0x37/0x7c
 ? ath5k_eeprom_read_pcal_info_5111+0x126a/0x1390 [ath5k]
 kasan_report+0xe/0x20
 ath5k_eeprom_read_pcal_info_5111+0x126a/0x1390 [ath5k]
 ? apic_timer_interrupt+0xa/0x20
 ? ath5k_eeprom_init_11a_pcal_freq+0xbc0/0xbc0 [ath5k]
 ? ath5k_pci_eeprom_read+0x228/0x3c0 [ath5k]
 ath5k_eeprom_init+0x2513/0x6290 [ath5k]
 ? ath5k_eeprom_init_11a_pcal_freq+0xbc0/0xbc0 [ath5k]
 ? usleep_range+0xb8/0x100
 ? apic_timer_interrupt+0xa/0x20
 ? ath5k_eeprom_read_pcal_info_2413+0x2f20/0x2f20 [ath5k]
 ath5k_hw_init+0xb60/0x1970 [ath5k]
 ath5k_init_ah+0x6fe/0x2530 [ath5k]
 ? kasprintf+0xa6/0xe0
 ? ath5k_stop+0x140/0x140 [ath5k]
 ? _dev_notice+0xf6/0xf6
 ? apic_timer_interrupt+0xa/0x20
 ath5k_pci_probe.cold+0x29a/0x3d6 [ath5k]
 ? ath5k_pci_eeprom_read+0x3c0/0x3c0 [ath5k]
 ? mutex_lock+0x89/0xd0
 ? ath5k_pci_eeprom_read+0x3c0/0x3c0 [ath5k]
 local_pci_probe+0xd3/0x160
 pci_device_probe+0x23f/0x3e0
 ? pci_device_remove+0x280/0x280
 ? pci_device_remove+0x280/0x280
 really_probe+0x209/0x5d0

Weakness: CWE-125 (Out-of-bounds Read)

## Which versions are affected by CVE-2021-47633?

It affects 1 product.


Products: Linux kernel.

## How do I fix CVE-2021-47633?

Apply the vendor's patch.

## Is CVE-2021-47633 being exploited?

There is no known exploitation of CVE-2021-47633 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-2021-47633 and fix it if it is affected.

What it is: CVE-2021-47633 is a high-severity memory corruption vulnerability in Linux kernel, published on 26 Feb 2025. 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-2021-47633 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-2021-47633/ (Markdown: https://insights.sbomify.com/CVE-2021-47633/index.md)
```

## Sources

- CVE record: https://www.cve.org/CVERecord?id=CVE-2021-47633
- NVD: https://nvd.nist.gov/vuln/detail/CVE-2021-47633
- OSV: https://osv.dev/vulnerability/CVE-2021-47633

---
From sbomify Insights: https://insights.sbomify.com/CVE-2021-47633/
Summaries are generated and may contain mistakes; the official description above is the record.