Vulnerability in Kernel (CVE-2025-39744)

Summary

Vulnerability in Kernel (CVE-2025-39744). Risk of unauthorized operations or information disclosure. Mitigation: upgrade to 6.6.103, 6.12.43, 6.15.11, 6.16.2 or later.

Original description

The description as published by the source.

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

rcu: Fix rcu_read_unlock() deadloop due to IRQ work

During rcu_read_unlock_special(), if this happens during irq_exit(), we
can lockup if an IPI is issued. This is because the IPI itself triggers
the irq_exit() path causing a recursive lock up.

This is precisely what Xiongfeng found when invoking a BPF program on
the trace_tick_stop() tracepoint As shown in the trace below. Fix by
managing the irq_work state correctly.

irq_exit()
__irq_exit_rcu()
/* in_hardirq() returns false after this /
preempt_count_sub(HARDIRQ_OFFSET)
tick_irq_exit()
tick_nohz_irq_exit()
tick_nohz_stop_sched_tick()
trace_tick_stop() / a bpf prog is hooked on this trace point /
__bpf_trace_tick_stop()
bpf_trace_run2()
rcu_read_unlock_special()
/ will send a IPI to itself */
irq_work_queue_on(&rdp->defer_qs_iw, rdp->cpu);

A simple reproducer can also be obtained by doing the following in
tick_irq_exit(). It will hang on boot without the patch:

static inline void tick_irq_exit(void)
{

rcu_read_lock();
WRITE_ONCE(current->rcu_read_unlock_special.b.need_qs, true);
rcu_read_unlock();

[neeraj: Apply Frederic's suggested fix for PREEMPT_RT]

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-2025-39744 has been found in Kernel.
Risk of unauthorized operations or information disclosure.
What to do: upgrade Kernel to 6.6.103, 6.12.43, 6.15.11, 6.16.2 or later.
If unsure, ask your IT team or search "Kernel CVE-2025-39744" on the vendor's site.

CVE-2025-39744 (Kernel)
Patched: 6.6.103, 6.12.43, 6.15.11, 6.16.2 — 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.

📍 Affected scope

Check the vendor advisory for the affected versions of Kernel.

🔥 Severity

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

🔧 How to fix

Update to 6.6.103, 6.12.43, 6.15.11, 6.16.2.

🛡️ 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 6.6.103, 6.12.43, 6.15.11, 6.16.2
```
ステージング環境で 6.6.103, 6.12.43, 6.15.11, 6.16.2 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":"5.3.0"},{"fixed":"6.6.103"}]},{"type":"ECOSYSTEM","events":[{"introduced":"6.7.0"},{"fixed":"6.12.43"}]},{"type":"ECOSYSTEM","events":[{"introduced":"6.13.0"},{"fixed":"6.15.11"}]},{"type":"ECOSYSTEM","events":[{"introduced":"6.16.0"},{"fixed":"6.16.2"}]}]

Fix status by distribution

Fixed packages published by each distribution for this CVE

BellSoft Alpaquita BELL-CVE-2025-39744 linux-lts
Debian DEBIAN-CVE-2025-39744 linux
Ubuntu UBUNTU-CVE-2025-39744 linux