Unchecked Input for Loop Condition Affecting kernel-modules-internal package, versions *
Threat Intelligence
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Test your applications- Snyk IDSNYK-RHEL8-KERNELMODULESINTERNAL-21035045
- published16 Oct 2026
- disclosed17 Sept 2026
Introduced: 17 Sep 2026
NewCVE-2026-90058 (opens in a new tab)How to fix?
There is no fixed version for RHEL:8 kernel-modules-internal.
NVD Description
Note: Versions mentioned in the description apply only to the upstream kernel-modules-internal package and not the kernel-modules-internal package as distributed by RHEL.
See How to fix? for RHEL:8 relevant fixed versions and status.
In the Linux kernel, the following vulnerability has been resolved:
net/sched: bound qdisc_pkt_len to prevent qdisc soft lockup
qdisc_get_stab() accepts a user-supplied size table, and __qdisc_calculate_pkt_len() amplifies qdisc_pkt_len() through the overhead, the size-table data (u16), and size_log (up to STAB_SIZE_LOG_MAX). A crafted stab can therefore set qdisc_pkt_len() to ~1 GiB for an ordinary skb. Per-flow deficit schedulers such as DRR and ETS replenish one quantum per loop iteration; with a tiny quantum (1) they spin billions of times under the qdisc lock, producing a soft lockup / RCU stall as illustrated by vega@nebusec.ai.
Cap the final qdisc_pkt_len() to QDISC_PKT_LEN_MAX so the size-table amplification cannot drive deficit schedulers into an unbounded loop. A legitimate size table (e.g. qfq's overhead 999999999, which is handled by dropping) is still accepted.
Introduce cap QDISC_PKT_LEN_MAX (1 << 20) = 1 MiB which is well above
any legitimate single-skb wire length: the largest current skb->len
is GSO_MAX_SIZE (524280), and an ATM-style size table (53/48 cell tax)
amplifies that to 578 KB, both comfortably below 1 MiB. At the same
time, 1 MiB bounds the deficit refill loop to ~1M iterations per
packet with quantum=1, which completes in a few milliseconds well
under the demonstrated softlockup threshold (10^9 iterations).
Conditions to recreate the bug:
- CONFIG_NET_SCHED=y, CONFIG_NET_SCH_DRR=y (or CONFIG_NET_SCH_ETS=y).
- Attach a DRR (or ETS) root qdisc with a crafted TCA_STAB that amplifies qdisc_pkt_len to ~1 GiB (e.g. size_log=15, data=[32768]).
- Add a class with a tiny quantum of 1 and send one small packet; the deficit loop spins billions of times under the qdisc lock and trips the softlockup detector (panic with kernel.softlockup_panic=1).
- Reachable as root or from an unprivileged user in a fresh user+net namespace (unshare -Urn) with namespace-local CAP_NET_ADMIN.
References
- https://access.redhat.com/security/cve/CVE-2026-90058
- https://git.kernel.org/stable/c/0bc5a6280a132a2170c6fa742436e01b635f02de
- https://git.kernel.org/stable/c/16d21a27df3f50b7251c9388fc5a7ab22703b469
- https://git.kernel.org/stable/c/1a5c26e586481bc82abc19ac92c3d9f10518f525
- https://git.kernel.org/stable/c/448c34421b38ec7c93a0060a885218ca319d382b
- https://git.kernel.org/stable/c/4f0f4b09a95ef602fbdae948326beadd9c20eab3
- https://git.kernel.org/stable/c/6e78792d8ce1fa3561713860ee8086901dde4f99
- https://git.kernel.org/stable/c/82fdbf49b9f7528c82bf608cfa9710e5f81a198c
- https://git.kernel.org/stable/c/8f735d64382dcf162f4276d6699d03ad2f859c0b