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CVE-2026-90109— net: sched: fix 32-bit backlog wrap in gred, bfifo and plug enqueue

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，已修复以下漏洞： net: sched: 修复 gred、bfifo 和 plug 入队过程中的 32 位 backlog 溢出（wrap）问题 、 和 在判断是否允许数据包入队时，采用如下逻辑： 对于 gred 默认虚拟队列（VQ）： 对于 gred 已配置的虚拟队列： 对于 bfifo： 对于 plug： 其中， 和 均为 类型，而 返回的 为无符号整型（unsigned int）。因此，所有加法运算均在 32 位宽度下执行，当结果超过 2³² 时会发生整数回绕（wrap-around）

AI Predicted 5.5 Difficulty: Hard EPSS 0.20% · P9

Affected Version Matrix 10

VendorProduct Version RangeStatus
Linux Linux a3eb95f891d6130b1fc03dd07a8b54cf0a5c8ab8< 3fb51b3960342bbee563543f8d33710fd0fb5a96 affected
a3eb95f891d6130b1fc03dd07a8b54cf0a5c8ab8< 8b2d8c70b969bf84f9e248bfaf2a7135129f2eb6 affected
a3eb95f891d6130b1fc03dd07a8b54cf0a5c8ab8< d98b92f3d57976ae185238946ec5ea0be32195aa affected
a3eb95f891d6130b1fc03dd07a8b54cf0a5c8ab8< 4c660ee8c809637909f4f7eb1017f7b9401c75c4 affected
4.2 affected
< 4.2 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-2026-90109

Vulnerability Information
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Vulnerability Title
net: sched: fix 32-bit backlog wrap in gred, bfifo and plug enqueue
Source: CVE Program / CVE List V5
Vulnerability Description
In the Linux kernel, the following vulnerability has been resolved: net: sched: fix 32-bit backlog wrap in gred, bfifo and plug enqueue gred_enqueue(), bfifo_enqueue() and plug_enqueue() admit a packet when the current backlog plus the packet length fits within the queue limit: sch->qstats.backlog + qdisc_pkt_len(skb) <= sch->limit (gred default VQ) gred_backlog+qdisc_pkt_len(skb) <= q->limit (gred configured VQ) sch->qstats.backlog + qdisc_pkt_len(skb) <= sch->limit (bfifo) sch->qstats.backlog + skb->len <= q->limit (plug) sch->qstats.backlog and q->backlog are u32, and qdisc_pkt_len()/skb->len are unsigned int, so all sums are computed in 32 bits and wrap at 2^32. Once the true backlog exceeds 4 GiB the wrapped sum becomes small and admission keeps succeeding, so the queue grows without bound and the kernel can be driven to OOM. Promote the sums to u64 so admission stops once the true backlog exceeds the limit. The limit is u32, so the bounded queue stays below 2^32 and the stored u32 backlog never wraps. The bug can only be reproduced as root (albeit with ridiculous setup): attach a gred (or bfifo/plug) qdisc with a limit near 4 GiB, leaving the default VQ unconfigured (for gred), and drive >4 GiB of queued traffic (e.g. via a size table / stab to inflate qdisc_pkt_len, or sustained high-rate traffic). The u32 backlog+len sum wraps at 2^32, admission keeps succeeding, and the queue grows unboundedly to OOM.
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 a3eb95f891d6130b1fc03dd07a8b54cf0a5c8ab8 ~ 3fb51b3960342bbee563543f8d33710fd0fb5a96 -
Linux Linux 4.2 -

II. Public POCs for CVE-2026-90109

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III. Intelligence Information for CVE-2026-90109

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Patches & Fixes for CVE-2026-90109 (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

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Same vendor: Linux

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