Vulnerability in linux (DEBIAN-CVE-2026-89903)
Summary
Vulnerability in linux (DEBIAN-CVE-2026-89903). Successful exploitation can lead to full system takeover. Mitigation: upgrade to 6.12.111-1 or later.
Original description
The description as published by the source.
In the Linux kernel, the following vulnerability has been resolved: LoongArch: Do not save/restore percpu base register in rethook trampoline The rethook trampoline saves $r21 ($u0), the percpu base, into its frame at entry and restores it at exit. Inbetween rethook_trampoline_handler() may schedule via preempt_enable_notrace(). If the task migrates to another CPU, the frame's $r21 holds the old CPU's percpu base, and restoring it poisons $r21 on the new CPU. Until the next user->kernel transition heals $r21, all this_cpu_*() accesses (runqueues, RCU per-CPU data, timer tick programming, FPU ownership) hit the wrong CPU's percpu area. Under kretprobe-heavy preemptible load this can corrupt scheduler and timer state: scheduling-while-atomic splats, wrong-CPU RCU warnings, WARN_ON_ONCE(rq != this_rq()) in nohz_balance_exit_idle(), and CPUs parking in the idle loop with the constant timer never re-armed (hard lockup). Reproduces on a Loongson-3A6000 with kretprobes on VFS paths plus heavy file churn (OS install / unsquashfs). By convention $r21 always holds the current CPU's percpu base in kernel mode: SAVE_SOME() at exception entry reloads it only when coming from user mode, and RESTORE_SOME() restores it only when returning to user mode; the context-switch path never writes it. Therefore the live $r21 at trampoline exit is already correct, and nothing inbetween can change it legitimately (kernel C code cannot write a global register variable). The same flaw existed even i…
Source: OSV.dev (Open Source Vulnerabilities) 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 DEBIAN-CVE-2026-89903 has been found in linux.
Successful exploitation can lead to full system takeover.
What to do: upgrade linux to 6.12.111-1 or later.
If unsure, ask your IT team or search "linux DEBIAN-CVE-2026-89903" on the vendor's site.
DEBIAN-CVE-2026-89903 (linux)
Attack vector: local / no user interaction
Patched: 6.12.111-1 — 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.
A vulnerability (unclassified) exists in linux.
Check the vendor advisory for the affected versions of linux.
Severity: ?. Successful exploitation can lead to full system takeover.
Update to 6.12.111-1.
Until the patch is applied: disable the affected feature, apply WAF rules, or restrict access via network ACLs.
Search webserver/proxy logs for unusual request patterns matching this CVE's known IOCs. Run grep -r 'linux' . 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
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1Identify exposure identify
grep -r 'linux' . | 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
linuxを grep し、稼働しているサービス・バージョンを把握する。 -
2Apply patch patch
Upgrade linux to 6.12.111-1ステージング環境で 6.12.111-1 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。
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3Post-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
References
- advisory security-tracker.debian.org