Vulnerability in Kernel (CVE-2025-38338)

Summary

Vulnerability in Kernel (CVE-2025-38338). Risk of unauthorized operations or information disclosure. Exploitable via PG_locked. Mitigation: upgrade to 6.6.95, 6.12.35, 6.15.4 or later.

Original description

The description as published by the source.

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

fs/nfs/read: fix double-unlock bug in nfs_return_empty_folio()

Sometimes, when a file was read while it was being truncated by
another NFS client, the kernel could deadlock because folio_unlock()
was called twice, and the second call would XOR back the PG_locked
flag.

Most of the time (depending on the timing of the truncation), nobody
notices the problem because folio_unlock() gets called three times,
which flips PG_locked back off:

vfs_read, nfs_read_folio, ... nfs_read_add_folio,
nfs_return_empty_folio
vfs_read, nfs_read_folio, ... netfs_read_collection,
netfs_unlock_abandoned_read_pages
vfs_read, ... nfs_do_read_folio, nfs_read_add_folio,
nfs_return_empty_folio

The problem is that nfs_read_add_folio() is not supposed to unlock the
folio if fscache is enabled, and a nfs_netfs_folio_unlock() check is
missing in nfs_return_empty_folio().

Rarely this leads to a warning in netfs_read_collection():

------------[ cut here ]------------
R=0000031c: folio 10 is not locked
WARNING: CPU: 0 PID: 29 at fs/netfs/read_collect.c:133 netfs_read_collection+0x7c0/0xf00
[...]
Workqueue: events_unbound netfs_read_collection_worker
RIP: 0010:netfs_read_collection+0x7c0/0xf00
[...]
Call Trace:

netfs_read_collection_worker+0x67/0x80
process_one_work+0x12e/0x2c0
worker_thread+0x295/0x3a0

Most of the time, however, processes just get stuck forever in
folio_wait_bit_common(), wai…

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-2025-38338 has been found in Kernel.
Attackers can target a specific entry point like PG_locked over the network to misuse the product.
Risk of unauthorized operations or information disclosure.
What to do: upgrade Kernel to 6.6.95, 6.12.35, 6.15.4 or later.
If unsure, ask your IT team or search "Kernel CVE-2025-38338" on the vendor's site.

CVE-2025-38338 (Kernel)
Attack surface: PG_locked
Patched: 6.6.95, 6.12.35, 6.15.4 — 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 PG_locked.

📍 Affected scope

Check the vendor advisory for the affected versions of Kernel. Attack surface: PG_locked.

🔥 Severity

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

🔧 How to fix

Update to 6.6.95, 6.12.35, 6.15.4.

🛡️ 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 6.6.95, 6.12.35, 6.15.4
```
ステージング環境で 6.6.95, 6.12.35, 6.15.4 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":"6.4.0"},{"fixed":"6.6.95"}]},{"type":"ECOSYSTEM","events":[{"introduced":"6.7.0"},{"fixed":"6.12.35"}]},{"type":"ECOSYSTEM","events":[{"introduced":"6.13.0"},{"fixed":"6.15.4"}]}]

Fix status by distribution

Fixed packages published by each distribution for this CVE

BellSoft Alpaquita BELL-CVE-2025-38338 linux-lts Fixed in: 6.12.41-r0
Debian DEBIAN-CVE-2025-38338 linux Fixed in: 6.12.35-1
Ubuntu UBUNTU-CVE-2025-38338 linux-hwe-edge