Vulnerability in Kernel (CVE-2025-39879)

Summary

Vulnerability in Kernel (CVE-2025-39879). Risk of unauthorized operations or information disclosure. Exploitable via processed_in_fbatch. Mitigation: upgrade to 6.16.8 or later.

Original description

The description as published by the source.

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

ceph: always call ceph_shift_unused_folios_left()

The function ceph_process_folio_batch() sets folio_batch entries to
NULL, which is an illegal state. Before folio_batch_release() crashes
due to this API violation, the function ceph_shift_unused_folios_left()
is supposed to remove those NULLs from the array.

However, since commit ce80b76dd327 ("ceph: introduce
ceph_process_folio_batch() method"), this shifting doesn't happen
anymore because the "for" loop got moved to ceph_process_folio_batch(),
and now the i variable that remains in ceph_writepages_start()
doesn't get incremented anymore, making the shifting effectively
unreachable much of the time.

Later, commit 1551ec61dc55 ("ceph: introduce ceph_submit_write()
method") added more preconditions for doing the shift, replacing the
i check (with something that is still just as broken):

if ceph_process_folio_batch() fails, shifting never happens
if ceph_move_dirty_page_in_page_array() was never called (because
ceph_process_folio_batch() has returned early for some of various
reasons), shifting never happens
if processed_in_fbatch is zero (because ceph_process_folio_batch()
has returned early for some of the reasons mentioned above or
because ceph_move_dirty_page_in_page_array() has failed), shifting
never happens

Since those two commits, any problem in ceph_process_folio_batch()
could crash the kernel, e.g. this way:

BUG: kerne…

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-2025-39879 has been found in Kernel.
Attackers can target a specific entry point like processed_in_fbatch over the network to misuse the product.
Risk of unauthorized operations or information disclosure.
What to do: upgrade Kernel to 6.16.8 or later.
If unsure, ask your IT team or search "Kernel CVE-2025-39879" on the vendor's site.

CVE-2025-39879 (Kernel)
Attack vector: local / no user interaction
Attack surface: processed_in_fbatch / huge_zero_folio
Patched: 6.16.8 — 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 processed_in_fbatch.

📍 Affected scope

Check the vendor advisory for the affected versions of Kernel. Attack surface: processed_in_fbatch / huge_zero_folio.

🔥 Severity

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

🔧 How to fix

Update to 6.16.8.

🛡️ 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 6.16.8
```
ステージング環境で 6.16.8 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":"6.16.8"}]}]

Fix status by distribution

Fixed packages published by each distribution for this CVE

BellSoft Alpaquita BELL-CVE-2025-39879 linux-lts Fixed in: 6.18.35-r1
Debian DEBIAN-CVE-2025-39879 linux Fixed in: 6.16.8-1
Ubuntu UBUNTU-CVE-2025-39879 linux-hwe-edge