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CVE-2026-90076— net/sched: fq: add overflow bounds to quantum and initial quantum

Quick assessment

Affected
Linux Linux
Exploitation
No confirmed in-the-wild exploitation; assess based on exposure
Recommended action
Check the vendor advisory and references for a fixed version. If immediate upgrade is impossible, restrict exposure and increase monitoring.

在 Linux 内核中，以下漏洞已得到修复： net/sched: fq: 为 quantum 和 initial quantum 添加溢出边界检查 中计算 和 ，但未进行溢出检查。当网络设备具有非常大的 MTU（例如， 的 dummy 设备接受 MTU 值为 2147483634）时， 会返回 0x80000000；此时 2 倍和 10 倍的乘法在 32 位运算中发生回绕（wrap），结果变为 0，导致 。随后在 中，信用值补充（credit-refill）循环向 加上 0（因此 保持 <= 0），并通过 在 q

AI Predicted 7.0 Difficulty: Moderate EPSS 0.20% · P9

Affected Version Matrix 10

VendorProduct Version RangeStatus
Linux Linux afe4fd062416b158a8a8538b23adc1930a9b88dc< d16dac3925be95ad46e986d4b139c9898b6e227f affected
afe4fd062416b158a8a8538b23adc1930a9b88dc< f6b3e3848a5fca63438984acd6d9eceac80814c1 affected
afe4fd062416b158a8a8538b23adc1930a9b88dc< e35acd56f244d94355f9ab237c2ecc8fba5e6f04 affected
afe4fd062416b158a8a8538b23adc1930a9b88dc< 709f34f7c28dc4dd6c40343d101850f11e172312 affected
3.12 affected
< 3.12 unaffected
6.12.110≤ 6.12.* unaffected
6.18.52≤ 6.18.* unaffected
… +2 more rows
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I. Basic Information for CVE-2026-90076

Vulnerability Information
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Vulnerability Title
net/sched: fq: add overflow bounds to quantum and initial quantum
Source: CVE Program / CVE List V5
Vulnerability Description
In the Linux kernel, the following vulnerability has been resolved: net/sched: fq: add overflow bounds to quantum and initial quantum fq_init() computes quantum = 2 * psched_mtu() and initial_quantum = 10 * psched_mtu() with no overflow check. A device with a huge MTU (e.g. dummy with max_mtu == 0 accepting MTU 2147483634) makes psched_mtu() return 0x80000000; the 2 * and 10 * multiplications wrap to 0 in 32-bit arithmetic, so q->quantum == 0. Then in fq_dequeue() the credit-refill loop adds 0 to f->credit (which stays <= 0) and goto begin loops forever under the qdisc lock, creating a soft lockup. Clamp psched_mtu() to [1, 1 << 20] before multiplying so the product cannot wrap, then cap the result at 1 << 20, matching the bound already enforced on TCA_FQ_QUANTUM in fq_change(). Conditions to recreate the bug: a device whose MTU (plus hard_header_len) is large enough that 2 * psched_mtu() wraps (e.g. a dummy device with max_mtu == 0 accepting MTU 2147483634). Requires CAP_NET_ADMIN in a user namespace.
Source: CVE Program / CVE List V5
CVSS Information
N/A
Source: CVE Program / CVE List V5
Vulnerability Type
N/A
Source: CVE Program / CVE List V5

Affected Products

Vendor Product Affected Versions CPE Subscribe
Linux Linux afe4fd062416b158a8a8538b23adc1930a9b88dc ~ d16dac3925be95ad46e986d4b139c9898b6e227f -
Linux Linux 3.12 -

II. Public POCs for CVE-2026-90076

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III. Intelligence Information for CVE-2026-90076

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Patches & Fixes for CVE-2026-90076 (4)

Same Patch Batch · Linux · 2026-09-17 · 600 CVEs total

CVE-2026-90173 9.8 CRITICAL smb: smbdirect: free completion queues with ib_free_cq()
CVE-2026-92489 9.8 CRITICAL xfrm: Fix skb double-free in xfrm_dev_direct_output()
CVE-2026-90104 9.8 CRITICAL NFSv4.1: zero referring call lists before decoding
CVE-2026-90235 9.8 CRITICAL sunrpc: xprtsock: annotate shared socket callbacks with READ_ONCE/WRITE_ONCE
CVE-2026-90151 9.8 CRITICAL NFSv4: remove callback IDR entry on client allocation failure
CVE-2026-90110 9.4 CRITICAL inetpeer: randomize RB-tree node comparison using SipHash
CVE-2026-90414 9.1 CRITICAL IB/isert: reject PDUs declaring more data than was received
CVE-2026-90413 9.1 CRITICAL IB/isert: reject login PDUs declaring more data than was received
CVE-2026-90230 9.1 CRITICAL nvmet: fix heap out-of-bounds read in nvmet_auth_negotiate()
CVE-2026-90381 8.8 HIGH wifi: mt76: fix handling channel context with different bands in mt76_switch_vif_chanctx()
CVE-2026-90329 8.8 HIGH HID: synchronize input before cleaning up a failed probe
CVE-2026-90162 8.8 HIGH ksmbd: defer publishing granted locks to prevent UAF/double-free race
CVE-2026-90357 8.8 HIGH wifi: mt76: mt7915: unlink TWT flow if the MCU rejects the agreement
CVE-2026-90367 8.8 HIGH wifi: mt76: mt7996: hold dev->mt76.mutex while disabling tx worker in SER
CVE-2026-90371 8.8 HIGH wifi: mt76: fix RXDMAD_C buffer recycling race
CVE-2026-93042 8.8 HIGH dmaengine: dw-edma: Terminate all descriptors without callbacks
CVE-2026-90425 8.8 HIGH iommu/tegra241-cmdqv: Require exactly one Stream ID for a vSID
CVE-2026-90240 8.8 HIGH iommu/vt-d: Flush context cache with correct SID when tearing down aliases
CVE-2026-90379 8.8 HIGH wifi: mt76: mt7921: Add PCIe AER handler support to prevent system crash
CVE-2026-90256 8.8 HIGH Bluetooth: L2CAP: use proto_lock for l2cap_data to fix l2cap_disconn_ind

Showing top 20 of 600 CVEs. View all on vendor page &rarr; →

IV. Related Vulnerabilities

Same product: Linux
Same vendor: Linux

V. Comments for CVE-2026-90076

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