{"id":"CVE-2026-90058","title":"In the Linux kernel, the following vulnerability has been resolved:\n\nnet/sched: bound qdisc_pkt_len to prevent qdisc soft lockup\n\nqdisc_get_stab() accepts a user-supplied size table, and\n__qdisc_calculate_pkt_len() amplifies qdisc_pkt_le…","summary":"In the Linux kernel, the following vulnerability has been resolved:\n\nnet/sched: bound qdisc_pkt_len to prevent qdisc soft lockup\n\nqdisc_get_stab() accepts a user-supplied size table, and\n__qdisc_calculate_pkt_len() amplifies qdisc_pkt_le…","severity":"none","vendor":"Linux","product":"Linux","affected":["Linux >= 1da177e4c3f41524e886b7f1b8a0c1fc7321cac2 < 4f0f4b09a95ef602fbdae948326beadd9c20eab3","Linux >= 1da177e4c3f41524e886b7f1b8a0c1fc7321cac2 < 0bc5a6280a132a2170c6fa742436e01b635f02de","Linux >= 1da177e4c3f41524e886b7f1b8a0c1fc7321cac2 < 448c34421b38ec7c93a0060a885218ca319d382b","Linux >= 1da177e4c3f41524e886b7f1b8a0c1fc7321cac2 < 82fdbf49b9f7528c82bf608cfa9710e5f81a198c","Linux >= 1da177e4c3f41524e886b7f1b8a0c1fc7321cac2 < 6e78792d8ce1fa3561713860ee8086901dde4f99","Linux >= 1da177e4c3f41524e886b7f1b8a0c1fc7321cac2 < 1a5c26e586481bc82abc19ac92c3d9f10518f525","Linux >= 1da177e4c3f41524e886b7f1b8a0c1fc7321cac2 < 16d21a27df3f50b7251c9388fc5a7ab22703b469","Linux >= 1da177e4c3f41524e886b7f1b8a0c1fc7321cac2 < 8f735d64382dcf162f4276d6699d03ad2f859c0b","Linux 2.6.12"],"published":"2026-09-17","updated":"2026-09-17","sourceUpdated":"2026-09-17T17:16:54.440","source":"NVD","sourceUrl":"https://nvd.nist.gov/vuln/detail/CVE-2026-90058","references":[{"url":"https://git.kernel.org/stable/c/0bc5a6280a132a2170c6fa742436e01b635f02de","label":"416baaa9-dc9f-4396-8d5f-8c081fb06d67"},{"url":"https://git.kernel.org/stable/c/16d21a27df3f50b7251c9388fc5a7ab22703b469","label":"416baaa9-dc9f-4396-8d5f-8c081fb06d67"},{"url":"https://git.kernel.org/stable/c/1a5c26e586481bc82abc19ac92c3d9f10518f525","label":"416baaa9-dc9f-4396-8d5f-8c081fb06d67"},{"url":"https://git.kernel.org/stable/c/448c34421b38ec7c93a0060a885218ca319d382b","label":"416baaa9-dc9f-4396-8d5f-8c081fb06d67"},{"url":"https://git.kernel.org/stable/c/4f0f4b09a95ef602fbdae948326beadd9c20eab3","label":"416baaa9-dc9f-4396-8d5f-8c081fb06d67"},{"url":"https://git.kernel.org/stable/c/6e78792d8ce1fa3561713860ee8086901dde4f99","label":"416baaa9-dc9f-4396-8d5f-8c081fb06d67"},{"url":"https://git.kernel.org/stable/c/82fdbf49b9f7528c82bf608cfa9710e5f81a198c","label":"416baaa9-dc9f-4396-8d5f-8c081fb06d67"},{"url":"https://git.kernel.org/stable/c/8f735d64382dcf162f4276d6699d03ad2f859c0b","label":"416baaa9-dc9f-4396-8d5f-8c081fb06d67"}],"tags":["nvd","cve.org"],"ingestedAt":"2026-09-17T16:21:47.902Z","epss":0.0022,"epssPercentile":0.11068,"slug":"CVE-2026-90058","body":"## Overview\n\nIn the Linux kernel, the following vulnerability has been resolved:\n\nnet/sched: bound qdisc_pkt_len to prevent qdisc soft lockup\n\nqdisc_get_stab() accepts a user-supplied size table, and\n__qdisc_calculate_pkt_len() amplifies qdisc_pkt_len() through the\noverhead, the size-table data (u16), and size_log (up to\nSTAB_SIZE_LOG_MAX). A crafted stab can therefore set qdisc_pkt_len()\nto ~1 GiB for an ordinary skb. Per-flow deficit schedulers such as\nDRR and ETS replenish one quantum per loop iteration; with a tiny\nquantum (1) they spin billions of times under the qdisc lock,\nproducing a soft lockup / RCU stall as illustrated by vega@nebusec.ai.\n\nCap the final qdisc_pkt_len() to QDISC_PKT_LEN_MAX so the size-table\namplification cannot drive deficit schedulers into an unbounded loop.\nA legitimate size table (e.g. qfq's overhead 999999999, which is\nhandled by dropping) is still accepted.\n\nIntroduce cap QDISC_PKT_LEN_MAX (1 << 20) = 1 MiB which is well above\nany legitimate single-skb wire length: the largest current skb->len\nis GSO_MAX_SIZE (524280), and an ATM-style size table (53/48 cell tax)\namplifies that to ~578 KB, both comfortably below 1 MiB. At the same\ntime, 1 MiB bounds the deficit refill loop to ~1M iterations per\npacket with quantum=1, which completes in a few milliseconds well\nunder the demonstrated softlockup threshold (~10^9 iterations).\n\nConditions to recreate the bug:\n- CONFIG_NET_SCHED=y, CONFIG_NET_SCH_DRR=y (or CONFIG_NET_SCH_ETS=y).\n- Attach a DRR (or ETS) root qdisc with a crafted TCA_STAB that\n  amplifies qdisc_pkt_len to ~1 GiB (e.g. size_log=15, data=[32768]).\n- Add a class with a tiny quantum of 1 and send one small packet; the\n  deficit loop spins billions of times under the qdisc lock and trips\n  the softlockup detector (panic with kernel.softlockup_panic=1).\n- Reachable as root or from an unprivileged user in a fresh user+net\n  namespace (unshare -Urn) with namespace-local CAP_NET_ADMIN.\n\n## Remediation\n\nRefer to the linked advisories for vendor-supplied fixes and affected version ranges.","depth":"sunlit","depthScore":3,"depthScoreParts":{"impact":2.8,"likelihood":0,"exploitation":0,"ransomware":0},"changes":[]}