CVE Catalog

CVE-2026-98012

Unknown
Published: Translated: NVD NIST

Summary

In the Linux kernel, sfq_change() accepted any non-negative quantum (only rejecting (int)ctl->quantum < 0). With a crafted size table qdisc_pkt_len reached ~2 GiB, so quantum=1 made the deficit-refill loop spin ~2^31 times under the qdisc lock, causing a soft lockup and denial of service.

Risk Assessment

A local attacker with CAP_NET_ADMIN privileges (obtainable in a namespace via unshare -Urn) can trigger a system hang through a soft lockup, causing denial of service.

Recommendation

Update the Linux kernel to a version containing the fix that clamps quantum to max(256U, ...) and rejects quantum > 1<<20 with -EINVAL in sfq_change(), matching fq_codel_change().

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 in change path sfq_change() accepts any non-negative quantum (only rejects (int)ctl->quantum < 0). With a crafted size table qdisc_pkt_len reaches ~2 GiB, so quantum=1 makes the deficit-refill loop spin ~2^31 times under the qdisc lock (a soft lockup / denial of service). Add max(256U, ...) matching fq_codel_change(). Reject quantum > 1<<20 with -EINVAL, matching fq_codel_change() and the init clamp. Conditions to recreate the bug: CONFIG_NET_SCH_SFQ=y. Requires CAP_NET_ADMIN (namespace-local via unshare -Urn suffices). tc qdisc add dev dummy0 root sfq tc qdisc change dev dummy0 root sfq quantum 1 stab data 32768 size_log 15 cell_log 0

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