{"id":"CVE-2026-90072","published":"2026-09-17T17:16:56.250","lastModified":"2026-09-17T17:16:56.250","description":"In the Linux kernel, the following vulnerability has been resolved:\n\nnet/sched: sfq: clamp quantum to avoid signed overflow soft lockup\n\nsfq_init() sets q->quantum = psched_mtu(qdisc_dev(sch)) (unsigned). A\ndevice with a huge MTU (e.g. dummy with max_mtu == 0 accepting MTU\n2147483634) makes psched_mtu() return 0x80000000, so slot->allot = INT_MIN\nand INT_MIN + INT_MIN toggles between INT_MIN and 0 forever, spinning\nsfq_dequeue() under the qdisc lock.\n\nClamp the quantum to [256, 1 << 20] so the refill loop terminates. The\nlower bound also covers q->quantum == 0 (psched_mtu() returning 0),\nwhich spins sfq_dequeue() identically. sfq_change() already rejects a\nnegative quantum, so only the init path was exposed.\n\nConditions to recreate the bug: a device whose MTU (plus\nhard_header_len) wraps psched_mtu() into the sign bit (e.g. a dummy\ndevice with max_mtu == 0 accepting MTU 2147483634). Requires\nCAP_NET_ADMIN in a user namespace.","cvssScore":null,"cvssSeverity":null,"cvssVector":null,"cwes":[],"vendors":[],"products":[],"references":[{"url":"https://git.kernel.org/stable/c/2017c355a5a1af77736cd1739fe922f69b5652dc","tags":[]},{"url":"https://git.kernel.org/stable/c/6581a82bf08ba5d4e2a6d4e3080df43315b296c4","tags":[]},{"url":"https://git.kernel.org/stable/c/816e90057ab1879562a5b7cc688e35bb9027ae97","tags":[]},{"url":"https://git.kernel.org/stable/c/86799499585af06a9431c9e7782658667bd62650","tags":[]},{"url":"https://git.kernel.org/stable/c/9d782c662879c3adaaca30e05c36910ad11b9e54","tags":[]},{"url":"https://git.kernel.org/stable/c/aeb8196ecb95146e3410f635628e6cd47352b3e5","tags":[]},{"url":"https://git.kernel.org/stable/c/d72dbdfaeb5b9b8d884e0e036c3442754379ef74","tags":[]},{"url":"https://git.kernel.org/stable/c/da16c31517cd2c06bb2c78c73e91ae192c01c426","tags":[]}],"exploitRefs":[],"hasPoc":false,"ai":null}