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CVE-2025-40083— net/sched: sch_qfq: Fix null-deref in agg_dequeue

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，该漏洞源于未检查cl->qdisc->ops->peek返回值，可能导致空指针取消引用。

AI Predicted 6.5 Difficulty: Easy EPSS 0.21% · P10

Possible ATT&CK Techniques 1 AI

T1211 · Exploitation for Stealth

Affected Version Matrix 16

VendorProduct Version RangeStatus
Linux Linux 462dbc9101acd38e92eda93c0726857517a24bbd< 71d84658a61322e5630c85c5388fc25e4a2d08b2 affected
462dbc9101acd38e92eda93c0726857517a24bbd< 99fc137f178797204d36ac860dd8b31e35baa2df affected
462dbc9101acd38e92eda93c0726857517a24bbd< 1bed56f089f09b465420bf23bb32985c305cfc28 affected
462dbc9101acd38e92eda93c0726857517a24bbd< 3c2a8994807623c7655ece205667ae2cf74940aa affected
462dbc9101acd38e92eda93c0726857517a24bbd< 6ffa9d66187188e3068b5a3895e6ae1ee34f9199 affected
462dbc9101acd38e92eda93c0726857517a24bbd< 6ff8e74c8f8a68ec07ef837b95425dfe900d060f affected
462dbc9101acd38e92eda93c0726857517a24bbd< dd831ac8221e691e9e918585b1003c7071df0379 affected
3.8 affected
… +8 more rows
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I. Basic Information for CVE-2025-40083

Vulnerability Information
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Vulnerability Title
net/sched: sch_qfq: Fix null-deref in agg_dequeue
Source: CVE Program / CVE List V5
Vulnerability Description
In the Linux kernel, the following vulnerability has been resolved: net/sched: sch_qfq: Fix null-deref in agg_dequeue To prevent a potential crash in agg_dequeue (net/sched/sch_qfq.c) when cl->qdisc->ops->peek(cl->qdisc) returns NULL, we check the return value before using it, similar to the existing approach in sch_hfsc.c. To avoid code duplication, the following changes are made: 1. Changed qdisc_warn_nonwc(include/net/pkt_sched.h) into a static inline function. 2. Moved qdisc_peek_len from net/sched/sch_hfsc.c to include/net/pkt_sched.h so that sch_qfq can reuse it. 3. Applied qdisc_peek_len in agg_dequeue to avoid crashing.
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，该漏洞源于未检查cl->qdisc->ops->peek返回值，可能导致空指针取消引用。
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 462dbc9101acd38e92eda93c0726857517a24bbd ~ 71d84658a61322e5630c85c5388fc25e4a2d08b2 -
Linux Linux 3.8 -

II. Public POCs for CVE-2025-40083

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III. Intelligence Information for CVE-2025-40083

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Patches & Fixes for CVE-2025-40083 (1)

Same Patch Batch · Linux · 2025-10-29 · 4 CVEs total

CVE-2023-7324 8.1 HIGH scsi: ses: Fix possible addl_desc_ptr out-of-bounds accesses
CVE-2025-40084 7.1 HIGH ksmbd: transport_ipc: validate payload size before reading handle
CVE-2025-40085 ALSA: usb-audio: Fix NULL pointer deference in try_to_register_card

IV. Related Vulnerabilities

Same product: Linux
Same vendor: Linux

V. Comments for CVE-2025-40083

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