CVE-2026-89902

Description

In the Linux kernel, the following vulnerability has been resolved: LoongArch: Avoid preempt count underflow without probe LoongArch uses break 11 for the breakpoint placed after an instruction that Kprobes executes out of line. Since userspace can issue the same break instruction, do_bp() can reach kprobe_singlestep_handler() when there is no current probe. The handler actually returns false in this case, but it first calls preempt_enable_no_resched(). The corresponding preempt_disable() is done by kprobe_breakpoint_handler() on a real Kprobe hit, so it has not run here. As a result, an ordinary userspace breakpoint (code 11) underflows the current task's preempt count. This also makes in_interrupt() return true until the task schedules. One visible consequence is the socket cgroup attribution: cgroup_sk_alloc() treats the allocation as interrupt context and assigns the socket to the root cgroup. A socket opened from the SIGTRAP handler can then avoid a BPF_CGROUP_INET_SOCK_CREATE policy attached to the task's own cgroup. Return as soon as kprobe_running() reports no active probe. The same check has appeared in [PATCH v10 2/4] of the original LoongArch Kprobes series, but was dropped before the feature reached mainline.

Gravité et risque d'exploitation

CVE-2026-89902 obtient un score CVSS de 7.8/10, soit une gravité élevée. Selon le modèle EPSS, la probabilité qu'elle soit exploitée dans les 30 prochains jours est de 0.18 %, ce qui la place devant 6.6 % des CVE référencées.

Que faire ?

• Vérifiez si Linux (versions <=6.12.*, 0, 6d4cc40fb5f58147defc6c0e9d86e6232fe31616, 6.18.51, <ff40e597d5d98c0c45a4d09df8177202fac9520e, <6.3, <a1cb727fa27c2d9c7859729cd90db7bc0f46957f, <=6.6.*, 7.2.5, 6.6.157, 6.3, <72ce4b24676e8b3b75376c4c559dd81c1ac52d5a, <=6.18.*, <c4357ebeee63cb8da1446fc936573a34e68b0f71, <=7.2.*, 6.12.110, <=*, <76395109a051b53860faaec96522ef08ae9e8e27, 7.3) est présent sur votre parc.
• Appliquez le correctif ou la version corrigée indiqués dans les références de l'éditeur.
• À défaut de correctif, limitez l'exposition (filtrage réseau, désactivation du composant).
• Automatisez la détection : les agents CVE Heimdall (gratuits, open source) corrèlent l'inventaire de vos serveurs avec la base CVE.

Références

• https://git.kernel.org/stable/c/ff40e597d5d98c0c45a4d09df8177202fac9520e
• https://git.kernel.org/stable/c/a1cb727fa27c2d9c7859729cd90db7bc0f46957f
• https://git.kernel.org/stable/c/76395109a051b53860faaec96522ef08ae9e8e27
• https://git.kernel.org/stable/c/c4357ebeee63cb8da1446fc936573a34e68b0f71
• https://git.kernel.org/stable/c/72ce4b24676e8b3b75376c4c559dd81c1ac52d5a