# CVE-2026-53402: fbdev: fbcon: fix out-of-bounds read in err_out of fbcon_do_set_font()

> A local attacker can trigger an out-of-bounds read in the Linux kernel's fbcon driver to disclose kernel memory.

- **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:** 19 Jul 2026
- **Updated:** 19 Oct 2026
- **Also known as:** AZL-92525, BELL-CVE-2026-53402, DEBIAN-CVE-2026-53402, GHSA-jxr7-x2hm-5g42, ROOT-OS-DEBIAN-11-CVE-2026-53402, ROOT-OS-DEBIAN-12-CVE-2026-53402, ROOT-OS-UBUNTU-2204-CVE-2026-53402, UBUNTU-CVE-2026-53402

## What is CVE-2026-53402?

CVE-2026-53402 is a high-severity vulnerability in Linux kernel, published on 19 Jul 2026. 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: fbcon: fix out-of-bounds read in err_out of fbcon_do_set_font()

When fbcon_do_set_font() fails (e.g., due to a memory allocation failure
inside vc_resize() under heavy memory pressure), it jumps to the `err_out`
label to roll back the console state. However, the current rollback logic
forgets to restore the `hi_font` state, leading to a severe state machine
corruption.

Earlier in the function, `set_vc_hi_font()` might be called to change
`vc->vc_hi_font_mask` and mutate the screen buffer. If `vc_resize()`
subsequently fails, the `err_out` path restores `vc_font.charcount`
but entirely skips rolling back the `vc_hi_font_mask` and the screen
buffer.

This mismatch leaves the terminal in a desynchronized state. Because
`vc_hi_font_mask` remains set, the VT subsystem will still accept
character indices greater than 255 from userspace and write them to the
screen buffer. Subsequent rendering calls (e.g., `fbcon_putcs()`) will
then use these inflated indices to access the reverted, 256-character
font array, leading to a deterministic out-of-bounds read and potential
kernel memory disclosure.

Fix this by adding the missing rollback logic for the `hi_font` mask
and screen buffer in the error path.

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

## Which versions are affected by CVE-2026-53402?

It affects 1 product.


Products: Linux kernel.

## How do I fix CVE-2026-53402?

Apply the vendor's patch.

## Is CVE-2026-53402 being exploited?

There is no known exploitation of CVE-2026-53402 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-2026-53402 and fix it if it is affected.

What it is: CVE-2026-53402 is a high-severity vulnerability in Linux kernel, published on 19 Jul 2026. 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-2026-53402 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-2026-53402/ (Markdown: https://insights.sbomify.com/CVE-2026-53402/index.md)
```

## Sources

- CVE record: https://www.cve.org/CVERecord?id=CVE-2026-53402
- NVD: https://nvd.nist.gov/vuln/detail/CVE-2026-53402
- OSV: https://osv.dev/vulnerability/CVE-2026-53402

---
From sbomify Insights: https://insights.sbomify.com/CVE-2026-53402/
Summaries are generated and may contain mistakes; the official description above is the record.