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CVE-2025-39766— net/sched: Make cake_enqueue return NET_XMIT_CN when past buffer_limit

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.

Linux kernel是美国Linux基金会的开源操作系统Linux所使用的内核。 Linux kernel存在安全漏洞，该漏洞源于cake_enqueue在超过buffer_limit时未正确返回NET_XMIT_CN，可能导致错误触发htb_activate警告。

AI Predicted 5.5 Difficulty: Trivial EPSS 0.18% · P8

Possible ATT&CK Techniques 1 AI

T1499 · Endpoint Denial of Service

Affected Version Matrix 18

VendorProduct Version RangeStatus
Linux Linux 046f6fd5daefac7f5abdafb436b30f63bc7c602b< 7689ab22de36f8db19095f6bdf11f28cfde92f5c affected
046f6fd5daefac7f5abdafb436b30f63bc7c602b< de04ddd2980b48caa8d7e24a7db2742917a8b280 affected
046f6fd5daefac7f5abdafb436b30f63bc7c602b< 0dacfc5372e314d1219f03e64dde3ab495a5a25e affected
046f6fd5daefac7f5abdafb436b30f63bc7c602b< 710866fc0a64eafcb8bacd91bcb1329eb7e5035f affected
046f6fd5daefac7f5abdafb436b30f63bc7c602b< aa12ee1c1bd260943fd6ab556d8635811c332eeb affected
046f6fd5daefac7f5abdafb436b30f63bc7c602b< ff57186b2cc39766672c4c0332323933e5faaa88 affected
046f6fd5daefac7f5abdafb436b30f63bc7c602b< 62d591dde4defb1333d202410609c4ddeae060b3 affected
046f6fd5daefac7f5abdafb436b30f63bc7c602b< 15de71d06a400f7fdc15bf377a2552b0ec437cf5 affected
… +10 more rows
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I. Basic Information for CVE-2025-39766

Vulnerability Information
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Vulnerability Title
net/sched: Make cake_enqueue return NET_XMIT_CN when past buffer_limit
Source: CVE Program / CVE List V5
Vulnerability Description
In the Linux kernel, the following vulnerability has been resolved: net/sched: Make cake_enqueue return NET_XMIT_CN when past buffer_limit The following setup can trigger a WARNING in htb_activate due to the condition: !cl->leaf.q->q.qlen tc qdisc del dev lo root tc qdisc add dev lo root handle 1: htb default 1 tc class add dev lo parent 1: classid 1:1 \ htb rate 64bit tc qdisc add dev lo parent 1:1 handle f: \ cake memlimit 1b ping -I lo -f -c1 -s64 -W0.001 127.0.0.1 This is because the low memlimit leads to a low buffer_limit, which causes packet dropping. However, cake_enqueue still returns NET_XMIT_SUCCESS, causing htb_enqueue to call htb_activate with an empty child qdisc. We should return NET_XMIT_CN when packets are dropped from the same tin and flow. I do not believe return value of NET_XMIT_CN is necessary for packet drops in the case of ack filtering, as that is meant to optimize performance, not to signal congestion.
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
Vulnerability Title
Linux kernel 安全漏洞
Source: CNNVD (China National Vulnerability Database)
Vulnerability Description
Linux kernel是美国Linux基金会的开源操作系统Linux所使用的内核。 Linux kernel存在安全漏洞，该漏洞源于cake_enqueue在超过buffer_limit时未正确返回NET_XMIT_CN，可能导致错误触发htb_activate警告。
Source: CNNVD (China National Vulnerability Database)
CVSS Information
N/A
Source: CNNVD (China National Vulnerability Database)
Vulnerability Type
N/A
Source: CNNVD (China National Vulnerability Database)

Affected Products

Vendor Product Affected Versions CPE Subscribe
Linux Linux 046f6fd5daefac7f5abdafb436b30f63bc7c602b ~ 7689ab22de36f8db19095f6bdf11f28cfde92f5c -
Linux Linux 4.19 -

II. Public POCs for CVE-2025-39766

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III. Intelligence Information for CVE-2025-39766

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Same Patch Batch · Linux · 2025-09-11 · 54 CVEs total

CVE-2025-39758 9.8 CRITICAL RDMA/siw: Fix the sendmsg byte count in siw_tcp_sendpages
CVE-2025-39761 8.8 HIGH wifi: ath12k: Decrement TID on RX peer frag setup error handling
CVE-2025-39750 8.8 HIGH wifi: ath12k: Correct tid cleanup when tid setup fails
CVE-2025-39790 8.4 HIGH bus: mhi: host: Detect events pointing to unexpected TREs
CVE-2025-39779 7.8 HIGH btrfs: subpage: keep TOWRITE tag until folio is cleaned
CVE-2025-39785 7.8 HIGH drm/hisilicon/hibmc: fix irq_request()'s irq name variable is local
CVE-2025-39786 7.8 HIGH iio: adc: ad7173: fix channels index for syscalib_mode
CVE-2025-39787 7.8 HIGH soc: qcom: mdt_loader: Ensure we don't read past the ELF header
CVE-2025-39740 7.8 HIGH drm/xe/migrate: prevent potential UAF
CVE-2025-39780 7.8 HIGH sched/ext: Fix invalid task state transitions on class switch
CVE-2025-39791 7.8 HIGH dm: dm-crypt: Do not partially accept write BIOs with zoned targets
CVE-2025-39770 7.5 HIGH net: gso: Forbid IPv6 TSO with extensions on devices with only IPV6_CSUM
CVE-2025-39738 7.3 HIGH btrfs: do not allow relocation of partially dropped subvolumes
CVE-2025-39789 7.3 HIGH crypto: x86/aegis - Add missing error checks
CVE-2025-39776 7.0 HIGH mm/debug_vm_pgtable: clear page table entries at destroy_args()
CVE-2025-39784 PCI: Fix link speed calculation on retrain failure
CVE-2025-39772 drm/hisilicon/hibmc: fix the hibmc loaded failed bug
CVE-2025-39782 jbd2: prevent softlockup in jbd2_log_do_checkpoint()
CVE-2025-39771 regulator: pca9450: Use devm_register_sys_off_handler
CVE-2025-39783 PCI: endpoint: Fix configfs group list head handling

Showing top 20 of 54 CVEs. View all on vendor page &rarr; →

IV. Related Vulnerabilities

Same product: Linux
Same vendor: Linux

V. Comments for CVE-2025-39766

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