Vulnerability in Kernel (CVE-2025-38433)

Summary

Vulnerability in Kernel (CVE-2025-38433). Risk of unauthorized operations or information disclosure. Exploitable via __runtime_fixup_32. Mitigation: upgrade to 6.15.5 or later.

Original description

The description as published by the source.

In the Linux kernel, the following vulnerability has been resolved:

riscv: fix runtime constant support for nommu kernels

the __runtime_fixup_32 function does not handle the case where val is
zero correctly (as might occur when patching a nommu kernel and referring
to a physical address below the 4GiB boundary whose upper 32 bits are all
zero) because nothing in the existing logic prevents the code from taking
the else branch of both nop-checks and emitting two nop instructions.

This leaves random garbage in the register that is supposed to receive the
upper 32 bits of the pointer instead of zero that when combined with the
value for the lower 32 bits yields an invalid pointer and causes a kernel
panic when that pointer is eventually accessed.

The author clearly considered the fact that if the lui is converted into
a nop that the second instruction needs to be adjusted to become an li
instead of an addi, hence introducing the addi_insn_mask variable, but
didn't follow that logic through fully to the case where the else branch
executes. To fix it just adjust the logic to ensure that the second else
branch is not taken if the first instruction will be patched to a nop.

Source: OSV.dev (Open Source Vulnerabilities) NVD OSV

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-2025-38433 has been found in Kernel.
Attackers can target a specific entry point like __runtime_fixup_32 over the network to misuse the product.
Risk of unauthorized operations or information disclosure.
What to do: upgrade Kernel to 6.15.5 or later.
If unsure, ask your IT team or search "Kernel CVE-2025-38433" on the vendor's site.

CVE-2025-38433 (Kernel)
Attack surface: __runtime_fixup_32 / val / else / nop
Patched: 6.15.5 — apply immediately
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

A vulnerability (unclassified) exists in Kernel. Attackers reach the vulnerable code path via __runtime_fixup_32.

📍 Affected scope

Check the vendor advisory for the affected versions of Kernel. Attack surface: __runtime_fixup_32 / val / else / nop.

🔥 Severity

Severity: ?. Risk of unauthorized operations or information disclosure.

🔧 How to fix

Update to 6.15.5.

🛡️ 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. Run grep -r 'Kernel' . against your dependency files (package-lock.json, requirements.txt, go.sum) to find affected services.

Response actions

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

1
Identify exposure identify
```
grep -r 'Kernel' . | grep -v node_modules
```
リポジトリと本番環境の依存ファイル (package-lock.json / requirements.txt / go.sum / Gemfile.lock 等) で Kernel を grep し、稼働しているサービス・バージョンを把握する。
2
Apply patch patch
```
Upgrade Kernel to 6.15.5
```
ステージング環境で 6.15.5 に上げて回帰テスト → 本番反映。回帰テストはアプリの主要ハッピーパスを含めること。
3
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":"6.15.0"},{"fixed":"6.15.5"}]}]

Fix status by distribution

Fixed packages published by each distribution for this CVE

BellSoft Alpaquita BELL-CVE-2025-38433 linux-lts Fixed in: 6.18.35-r1