CVE-2025-39766
Vulnerability Scoring
Analysis In Progress
CVE-2025-39766 Vulnerability Analysis & Exploit Details
CVE-2025-39766
Attack Complexity Details
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Attack Complexity:
Attack Complexity Analysis In Progress
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Attack Vector:
Attack Vector Under Analysis
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Privileges Required:
None
No authentication is required for exploitation.
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Scope:
Impact is confined to the initially vulnerable component.
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User Interaction:
None
No user interaction is necessary for exploitation.
CVE-2025-39766 Details
Status: Awaiting Analysis
Last updated: 🕕 03 Nov 2025, 18:16 UTC
Originally published on: 🕔 11 Sep 2025, 17:15 UTC
Time between publication and last update: 53 days
CVSS Release:
CVE-2025-39766 Vulnerability Summary
CVE-2025-39766: 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.
Assessing the Risk of CVE-2025-39766
Access Complexity Graph
The exploitability of CVE-2025-39766 depends on two key factors: attack complexity (the level of effort required to execute an exploit) and privileges required (the access level an attacker needs).
Exploitability Analysis for CVE-2025-39766
No exploitability data is available for CVE-2025-39766.
Understanding AC and PR
A lower complexity and fewer privilege requirements make exploitation easier. Security teams should evaluate these aspects to determine the urgency of mitigation strategies, such as patch management and access control policies.
Attack Complexity (AC) measures the difficulty in executing an exploit. A high AC means that specific conditions must be met, making an attack more challenging, while a low AC means the vulnerability can be exploited with minimal effort.
Privileges Required (PR) determine the level of system access necessary for an attack. Vulnerabilities requiring no privileges are more accessible to attackers, whereas high privilege requirements limit exploitation to authorized users with elevated access.
CVSS Score Breakdown Chart
Above is the CVSS Sub-score Breakdown for CVE-2025-39766, illustrating how Base, Impact, and Exploitability factors combine to form the overall severity rating. A higher sub-score typically indicates a more severe or easier-to-exploit vulnerability.
CIA Impact Analysis
Below is the Impact Analysis for CVE-2025-39766, showing how Confidentiality, Integrity, and Availability might be affected if the vulnerability is exploited. Higher values usually signal greater potential damage.
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Confidentiality:
None
CVE-2025-39766 does not compromise confidentiality.
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Integrity:
None
CVE-2025-39766 does not impact data integrity.
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Availability:
None
CVE-2025-39766 does not affect system availability.
CVE-2025-39766 References
External References
- https://git.kernel.org/stable/c/0dacfc5372e314d1219f03e64dde3ab495a5a25e
- https://git.kernel.org/stable/c/15de71d06a400f7fdc15bf377a2552b0ec437cf5
- https://git.kernel.org/stable/c/62d591dde4defb1333d202410609c4ddeae060b3
- https://git.kernel.org/stable/c/710866fc0a64eafcb8bacd91bcb1329eb7e5035f
- https://git.kernel.org/stable/c/7689ab22de36f8db19095f6bdf11f28cfde92f5c
- https://git.kernel.org/stable/c/aa12ee1c1bd260943fd6ab556d8635811c332eeb
- https://git.kernel.org/stable/c/de04ddd2980b48caa8d7e24a7db2742917a8b280
- https://git.kernel.org/stable/c/ff57186b2cc39766672c4c0332323933e5faaa88
- https://lists.debian.org/debian-lts-announce/2025/10/msg00007.html
- https://lists.debian.org/debian-lts-announce/2025/10/msg00008.html
CWE Common Weakness Enumeration
Unknown
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