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CVE-2026-53402 high CVSS 7.1

Out-of-Bounds Read in Linux kernel (CVE-2026-53402)

Summary

Vulnerability in Linux kernel (CVE-2026-53402). Confidential information can be exposed externally. Exploitable via err_out.

Original description

The description as published by the source.

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.

Source: GitHub Security Advisories (Global) NVD GitHub Advisory

Auto-generated summary

Assembled by SecPulse from the source data (CVSS, CWE, affected versions) using templates — no AI involved. Check the original description and references below for exact details.

A vulnerability tracked as CVE-2026-53402 has been found in Linux kernel.
Attackers can target a specific entry point like err_out over the network to misuse the product.
Confidential information can be exposed externally. CVSS score: 7.1/10.
What to do: apply the vendor's official patched release.
If unsure, ask your IT team or search "Linux kernel CVE-2026-53402" on the vendor's site.

CVE-2026-53402 (Linux kernel) — CWE-125 / CVSS v3 7.1
Attack vector: local / no user interaction
Attack surface: err_out / hi_font / vc_font.charcount / vc_hi_font_mask
Plan: 1) Audit SBOM/dependencies, 2) Stage→prod upgrade, 3) Add WAF/proxy monitoring on affected endpoints, 4) Hunt IOCs in logs.
Refs: see the GHSA / vendor advisory / patched release linked on this page.

❓ What is the problem

Out-of-bounds read (CWE-125) exists in Linux kernel. Attackers reach the vulnerable code path via err_out.

📍 Affected scope

Check the vendor advisory for the affected versions of Linux kernel. Attack surface: err_out / hi_font / vc_font.charcount / vc_hi_font_mask.

🔥 Severity

Severity: High (CVSS 7.1/10). Confidential information can be exposed externally.

🔧 How to fix

Update to the patched release per vendor advisory.

🛡️ Workaround

Until the patch is applied: disable the affected feature, apply WAF rules, or restrict access via network ACLs.

🔍 Detection

Search webserver/proxy logs for unusual request patterns matching this CVE's known IOCs. Audit SBOM/dependencies to find affected services.

Response actions

Concrete steps and command examples for SOC/SRE teams to execute in order

  1. 1
    Identify exposure identify 
    Audit SBOM/dependencies for affected components.

    資産台帳・SBOM・依存マニフェストで Linux kernel を使っているサービスとバージョンを洗い出す。

  2. 2
    Post-deployment verification verify 
    Confirm patched version is live in production

    パッチ適用後、ステージングで PoC または同等の悪用パターンを再現して脆弱性が閉じたことを確認。本番ではアクセスログ・WAF でアラート再発が無いか継続監視。

Affected packages

Linux Kernel
[{"type":"ECOSYSTEM","events":[{"introduced":"0"},{"fixed":"5.10.261"}]},{"type":"ECOSYSTEM","events":[{"introduced":"5.11.0"},{"fixed":"5.15.212"}]},{"type":"ECOSYSTEM","events":[{"introduced":"5.16.0"},{"fixed":"6.1.178"}]},{"type":"ECOSYSTEM","events":[{"introduced":"6.0.0"},{"fixed":"6.6.145"}]},{"type":"ECOSYSTEM","events":[{"introduced":"6.2.0"},{"fixed":"6.12.96"}]},{"type":"ECOSYSTEM","events":[{"introduced":"6.7.0"},{"fixed":"6.18.39"}]},{"type":"ECOSYSTEM","events":[{"introduced":"6.13.0"},{"fixed":"7.1.3"}]}]

Fix status by distribution

Fixed packages published by each distribution for this CVE

References

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