Unknown

CVE-2026-90058 — net/sched: bound qdisc_pkt_len to prevent qdisc soft lockup

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.

Published Sep 17, 2026 · Updated Oct 19, 2026 · Sources: NIST National Vulnerability Database, CVE Program (cve.org) e CISA ADP, GitHub Security Advisories · CNA: Linux

Low

Who exploits it and how urgent it is

A 0–100 score combining confirmed exploitation, ransomware and APT use, public exploits, EPSS and severity.

No exploitation signal in the sources consulted so far.

How the score was calculated

EPSS 0.2% (30-day exploitation probability)+2

The score orders the patch queue; it does not replace your asset context (internet exposure, criticality, compensating controls).

Triage

Is it exploited, how likely is exploitation, what does it touch, and how severe do the sources call it.

Exploitation

Not confirmed

Not in CISA KEV — an absence of record, not proof it is unexploited.

EPSS FIRST

0.22%

ahead of 11% of scored CVEs · Oct 19, 2026

Affects

Linux

CVSS base

—

Score not published yet.

Remediation

Fixes and mitigations documented by the sources — linked to the original advisory.

No fix documented by the sources we poll. That does not mean none exists: check the vendor advisory.

First 24 hours

Ordered from the record’s own fields — exposure first, because you cannot patch what you have not found. A rule-generated starting point.

Identify exposed assets running the affected vendor/product/version combinations (Linux Linux).
No fix documented in the sources: reduce exposure and monitor the vendor advisory.
Search available logs for exploit probes, errors and authentication anomalies.

Affected scope

Vendor, product and versions as the sources word them.

Vendor	Product	Versions	Status	Source
Linux	Linux	≥ 1da177e4c3f41524e886b7f1b8a0c1fc7321cac2 and < 4f0f4b09a95ef602fbdae948326beadd9c20eab3≥ 1da177e4c3f41524e886b7f1b8a0c1fc7321cac2 and < 0bc5a6280a132a2170c6fa742436e01b635f02de≥ 1da177e4c3f41524e886b7f1b8a0c1fc7321cac2 and < 448c34421b38ec7c93a0060a885218ca319d382b≥ 1da177e4c3f41524e886b7f1b8a0c1fc7321cac2 and < 82fdbf49b9f7528c82bf608cfa9710e5f81a198c≥ 1da177e4c3f41524e886b7f1b8a0c1fc7321cac2 and < 6e78792d8ce1fa3561713860ee8086901dde4f99≥ 1da177e4c3f41524e886b7f1b8a0c1fc7321cac2 and < 1a5c26e586481bc82abc19ac92c3d9f10518f525≥ 1da177e4c3f41524e886b7f1b8a0c1fc7321cac2 and < 16d21a27df3f50b7251c9388fc5a7ab22703b469≥ 1da177e4c3f41524e886b7f1b8a0c1fc7321cac2 and < 8f735d64382dcf162f4276d6699d03ad2f859c0b and 1 more version 2.6.12	Vulnerable	CVE Program (cve.org) e CISA ADP

EPSS over time FIRST

Oct 15, 2026 → Oct 19, 2026 · 4 reading(s) · max 0.22%

Detection

Read off the CVSS vector and the weakness class. Starting points, not tested rules.

Not enough vector or weakness data: use the affected application’s logs as a starting point.

application logs

Timeline

What happened to this CVE, newest first.

2026
Record published
Oct 15, 2026
Affected products added · linux/linux
Oct 15, 2026 · CVE Program (cve.org) e CISA ADP
Source status changed · → Received
Oct 15, 2026 · NIST National Vulnerability Database
Record created in this database
Oct 15, 2026 · NIST National Vulnerability Database
CVE published
Sep 17, 2026 · Linux

Source activity

Repeated readings are counted rather than listed.

1× References added · Oct 19, 2026 – Oct 19, 2026
1× Official description updated · Oct 15, 2026 – Oct 15, 2026

References

10 on the record

git.kernel.org/stable/c/82fdbf49b9f7528c82bf608cfa9710e5f81a198c
NIST National Vulnerability Database
git.kernel.org/stable/c/4f0f4b09a95ef602fbdae948326beadd9c20eab3
NIST National Vulnerability Database
git.kernel.org/stable/c/6e78792d8ce1fa3561713860ee8086901dde4f99
NIST National Vulnerability Database
git.kernel.org/stable/c/1a5c26e586481bc82abc19ac92c3d9f10518f525
NIST National Vulnerability Database
git.kernel.org/stable/c/16d21a27df3f50b7251c9388fc5a7ab22703b469
NIST National Vulnerability Database
nvd.nist.gov/vuln/detail/CVE-2026-90058
GitHub Security Advisories
github.com/advisories/GHSA-59qr-qww5-6w4f
GitHub Security Advisories
git.kernel.org/stable/c/0bc5a6280a132a2170c6fa742436e01b635f02de
NIST National Vulnerability Database
git.kernel.org/stable/c/448c34421b38ec7c93a0060a885218ca319d382b
NIST National Vulnerability Database
git.kernel.org/stable/c/8f735d64382dcf162f4276d6699d03ad2f859c0b
NIST National Vulnerability Database

Elsewhere on this site

Linux
every CVE for this vendor

Related CVEs (same products)

Unknown CVE-2026-98866 sched/cache: Introduce task_struct->sched_cache_grp to fix UAF 1d
Unknown CVE-2026-98867 dm-pcache: bound the logical key offset from persistent memory 1d
Unknown CVE-2026-98868 dm-pcache: reject a kset that overruns its segment 1d
Unknown CVE-2026-98856 kprobes: Skip disarmed probes when checking optkprobe overlap 1d
Unknown CVE-2026-98857 ipvs: bound LBLCR and LBLC cache growth 1d
Unknown CVE-2026-98858 io_uring: fix task_work add use-after-free with SQPOLL 1d

Not in any source we poll

Listed rather than left blank: an empty field and an unmeasured one look identical on screen, and only one is a reason to look elsewhere.

No CVSS score published by NVD, the CNA, CISA or GitHub so far.
No fixed version, patch or mitigation documented.
No CISA SSVC assessment.
No CWE classification.
No confirmed IOCs, IP addresses, domains, file hashes, or malware artifacts supplied.
No organization-specific asset inventory, compensating-control status, or patch deployment evidence supplied.
No exploit packet captures, log samples, or incident case IDs supplied.

Answered from this record

Text assembled only from the fields above — no additional claims.

What should defenders know first?

CVE-2026-90058 is "net/sched: bound qdisc_pkt_len to prevent qdisc soft lockup", rated Unknown. It affects Linux (Linux); versions are in the scope table. It is not in CISA KEV, which does not rule out exploitation. EPSS 0.22% estimates the probability of exploitation in 30 days; neither replaces your asset context. First verify whether exposed or business-critical assets run the affected versions, apply vendor fixes or mitigations, and preserve logs for review.

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