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CVE-2025-39766 (GCVE-0-2025-39766)

Vulnerability from cvelistv5 – Published: 2025-09-11 16:56 – Updated: 2026-06-11 18:44
VLAI
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
Impacted 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 Create a notification for this product.
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 Create a notification for this product.
Siemens SIMATIC CN 4100 Affected: 0 , < V5.0 (custom)
guessed Create a notification for this product.
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}



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Taxonomy of the tags.





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.


Detection rules are retrieved from Rulezet.


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.