# CVE-2025-40322: fbdev: bitblit: bound-check glyph index in bit_putcs*

> An out-of-bounds read in the Linux kernel framebuffer driver allows attackers to read memory beyond the font array boundaries.

- **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:** 8 Dec 2025
- **Updated:** 5 Aug 2026
- **Also known as:** BELL-CVE-2025-40322, DEBIAN-CVE-2025-40322, GHSA-hcc6-6437-vwm2, ROOT-OS-DEBIAN-12-CVE-2025-40322, ROOT-OS-DEBIAN-13-CVE-2025-40322, ROOT-OS-UBUNTU-2204-CVE-2025-40322, ROOT-OS-UBUNTU-2404-CVE-2025-40322, UBUNTU-CVE-2025-40322

## What is CVE-2025-40322?

CVE-2025-40322 is a high-severity vulnerability in Linux, published on 8 Dec 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:

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.

## Which versions are affected by CVE-2025-40322?


## How do I fix CVE-2025-40322?

Apply the vendor's patch.

## Is CVE-2025-40322 being exploited?

There is no known exploitation of CVE-2025-40322 in the wild and no public exploit code.

## Fix prompt for AI coding agents

```text
Check this codebase for CVE-2025-40322 and fix it if it is affected.

What it is: CVE-2025-40322 is a high-severity vulnerability in Linux, published on 8 Dec 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-2025-40322 in the wild and no public exploit code.

Affected product: Linux. 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-2025-40322/ (Markdown: https://insights.sbomify.com/CVE-2025-40322/index.md)
```

## Sources

- CVE record: https://www.cve.org/CVERecord?id=CVE-2025-40322
- NVD: https://nvd.nist.gov/vuln/detail/CVE-2025-40322
- OSV: https://osv.dev/vulnerability/CVE-2025-40322

---
From sbomify Insights: https://insights.sbomify.com/CVE-2025-40322/
Summaries are generated and may contain mistakes; the official description above is the record.