CVE-2025-39766 (GCVE-0-2025-39766)
Vulnerability from cvelistv5 – Published: 2025-09-11 16:56 – Updated: 2026-06-11 18:44
VLAI
EPSS
VEX
Title
net/sched: Make cake_enqueue return NET_XMIT_CN when past buffer_limit
Summary
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.
Severity
No CVSS data available.
SSVC
Exploitation: none
Automatable: no
Technical Impact: total
CISA Coordinator · CISA-ADP (v2.0.3)
Decision recorded 2026-06-10 20:40 UTC
Assigner
References
11 references
Impacted products
3 products
| Vendor | Product | Version | CPE status | |
|---|---|---|---|---|
| Linux | Linux |
Affected:
046f6fd5daefac7f5abdafb436b30f63bc7c602b , < 7689ab22de36f8db19095f6bdf11f28cfde92f5c
(git)
Affected: 046f6fd5daefac7f5abdafb436b30f63bc7c602b , < de04ddd2980b48caa8d7e24a7db2742917a8b280 (git) Affected: 046f6fd5daefac7f5abdafb436b30f63bc7c602b , < 0dacfc5372e314d1219f03e64dde3ab495a5a25e (git) Affected: 046f6fd5daefac7f5abdafb436b30f63bc7c602b , < 710866fc0a64eafcb8bacd91bcb1329eb7e5035f (git) Affected: 046f6fd5daefac7f5abdafb436b30f63bc7c602b , < aa12ee1c1bd260943fd6ab556d8635811c332eeb (git) Affected: 046f6fd5daefac7f5abdafb436b30f63bc7c602b , < ff57186b2cc39766672c4c0332323933e5faaa88 (git) Affected: 046f6fd5daefac7f5abdafb436b30f63bc7c602b , < 62d591dde4defb1333d202410609c4ddeae060b3 (git) Affected: 046f6fd5daefac7f5abdafb436b30f63bc7c602b , < 15de71d06a400f7fdc15bf377a2552b0ec437cf5 (git) |
guessed | |
| Linux | Linux |
Affected:
4.19
Unaffected: 0 , < 4.19 (semver) Unaffected: 5.4.297 , ≤ 5.4.* (semver) Unaffected: 5.10.241 , ≤ 5.10.* (semver) Unaffected: 5.15.190 , ≤ 5.15.* (semver) Unaffected: 6.1.149 , ≤ 6.1.* (semver) Unaffected: 6.6.103 , ≤ 6.6.* (semver) Unaffected: 6.12.44 , ≤ 6.12.* (semver) Unaffected: 6.16.4 , ≤ 6.16.* (semver) Unaffected: 6.17 , ≤ * (original_commit_for_fix) |
guessed | |
| Siemens | SIMATIC CN 4100 |
Affected:
0 , < V5.0
(custom)
|
guessed |
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Experimental. This forecast is provided for visualization only and may change without notice. Do not use it for operational decisions.
Forecast uses a logistic model when the trend is rising, or an exponential decay model when the trend is falling. Fitted via linearized least squares.
Sightings
| Author | Source | Type | Date | Other |
|---|
Nomenclature
- Seen: The vulnerability was mentioned, discussed, or observed by the user.
- Confirmed: The vulnerability has been validated from an analyst's perspective.
- Published Proof of Concept: A public proof of concept is available for this vulnerability.
- Exploited: The vulnerability was observed as exploited by the user who reported the sighting.
- Patched: The vulnerability was observed as successfully patched by the user who reported the sighting.
- Not exploited: The vulnerability was not observed as exploited by the user who reported the sighting.
- Not confirmed: The user expressed doubt about the validity of the vulnerability.
- Not patched: The vulnerability was not observed as successfully patched by the user who reported the sighting.
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The MITRE ATT&CK techniques below are AI-generated suggestions, inferred from the description of the
vulnerability by the CIRCL/vulnerability-attack-technique-classification-roberta-base
model, served locally by ML-Gateway.
They have not been verified by an analyst and are provided for guidance only.
The approach is described in our paper Mapping CVEs to MITRE ATT&CK Techniques: A Curated Gold-Set Classifier and the Limits of LLM-Assisted Label Expansion.
Browse all ATT&CK techniques and the vulnerabilities related to each.
The approach is described in our paper Mapping CVEs to MITRE ATT&CK Techniques: A Curated Gold-Set Classifier and the Limits of LLM-Assisted Label Expansion.
Browse all ATT&CK techniques and the vulnerabilities related to each.
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Related by attack behaviour
Vulnerabilities whose description is nearest to this one in the vector space of the CIRCL/vulnerability-attack-technique-biencoder model. This is a similarity search over the bi-encoder space (plain cosine), not a classification, and it has no measured accuracy.
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