CVE Catalog

CVE-2026-90072

Unknown
Published: Translated: NVD NIST

Summary

In the Linux kernel, the net/sched sfq module fails to clamp the quantum value. A device with a huge MTU makes slot->allot equal INT_MIN, and INT_MIN + INT_MIN toggles between INT_MIN and 0, causing an infinite loop in sfq_dequeue() and a soft lockup.

Risk Assessment

A user with CAP_NET_ADMIN in a user namespace can trigger a kernel soft lockup. This may lead to system hang and denial of service.

Recommendation

Update the Linux kernel to a version containing the fix that clamps quantum to [256, 1 << 20]. Consider restricting the ability to create user namespaces with CAP_NET_ADMIN.

Other vulnerabilities in Linux kernel

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Original NVD description (English source)

In the Linux kernel, the following vulnerability has been resolved: net/sched: sfq: clamp quantum to avoid signed overflow soft lockup sfq_init() sets q->quantum = psched_mtu(qdisc_dev(sch)) (unsigned). A device with a huge MTU (e.g. dummy with max_mtu == 0 accepting MTU 2147483634) makes psched_mtu() return 0x80000000, so slot->allot = INT_MIN and INT_MIN + INT_MIN toggles between INT_MIN and 0 forever, spinning sfq_dequeue() under the qdisc lock. Clamp the quantum to [256, 1 << 20] so the refill loop terminates. The lower bound also covers q->quantum == 0 (psched_mtu() returning 0), which spins sfq_dequeue() identically. sfq_change() already rejects a negative quantum, so only the init path was exposed. Conditions to recreate the bug: a device whose MTU (plus hard_header_len) wraps psched_mtu() into the sign bit (e.g. a dummy device with max_mtu == 0 accepting MTU 2147483634). Requires CAP_NET_ADMIN in a user namespace.

Vulnerability data from NVD (NIST) · CISA KEV · EPSS