CVE-2026-90072

Not scored yetLast modified Oct 19, 2026

Description

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.

Metrics

No CVSS score has been published yet.

Affected software

Source: the vendor's advisory (CNA). NVD analysis pending.

VendorProductVersions
LinuxLinux>= 1da177e4c3f41524e886b7f1b8a0c1fc7321cac2, < 86799499585af06a9431c9e7782658667bd62650; >= 1da177e4c3f41524e886b7f1b8a0c1fc7321cac2, < 2017c355a5a1af77736cd1739fe922f69b5652dc; >= 1da177e4c3f41524e886b7f1b8a0c1fc7321cac2, < 6581a82bf08ba5d4e2a6d4e3080df43315b296c4; >= 1da177e4c3f41524e886b7f1b8a0c1fc7321cac2, < 9d782c662879c3adaaca30e05c36910ad11b9e54; >= 1da177e4c3f41524e886b7f1b8a0c1fc7321cac2, < d72dbdfaeb5b9b8d884e0e036c3442754379ef74; >= 1da177e4c3f41524e886b7f1b8a0c1fc7321cac2, < aeb8196ecb95146e3410f635628e6cd47352b3e5; >= 1da177e4c3f41524e886b7f1b8a0c1fc7321cac2, < da16c31517cd2c06bb2c78c73e91ae192c01c426; >= 1da177e4c3f41524e886b7f1b8a0c1fc7321cac2, < 816e90057ab1879562a5b7cc688e35bb9027ae97
LinuxLinux2.6.12

References

Timeline

Published
Sep 17, 2026
Last modified
Oct 19, 2026
NVD status
Received

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CVE-2026-90072: Unscored | Vulnix