CVE-2025-39766net/sched: Make cake_enqueue return NET_XMIT_CN when past buffer_limit
- 7.8HighCVSS base score
- 0.19%Exploitation in 30 daysEPSS · top 91% of all CVEs
- NoKnown exploitednot in CISA's KEV catalog
- NonePublic exploitsnone known yet
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.
Timeline
ID reserved
By Linux
- 5 months later
· 5 months later
Published
- 9 months later
· 9 months later
Record updated
Changes after publication (a new score, a public exploit, EPSS crossing 1, 10 or 50 %, leaving KEV) are kept since November 2026; earlier ones are not known.
Scores
| Scored by | CVSS | Score | Vector |
|---|---|---|---|
| NVDNVD · Modified | 3.1 | High7.8 | CVSS:3.1/AV:L/AC:L/PR:L/UI:N/S:U/C:H/I:H/A:H |
- EPSS (exploitation in 30 days)
- 0.19% · top 91% of all CVEs (14 Nov 2026)
- CISA SSVC
- Exploitation: none · Automatable: no · Technical impact: total
The list uses the assigner's score when there is one, then CISA's, then NVD's: High 7.8.
Affected products
- affected 046f6fd5daefac7f5abdafb436b30f63bc7c602b – < 7689ab22de36f8db19095f6bdf11f28cfde92f5c
- affected 046f6fd5daefac7f5abdafb436b30f63bc7c602b – < de04ddd2980b48caa8d7e24a7db2742917a8b280
- affected 046f6fd5daefac7f5abdafb436b30f63bc7c602b – < 0dacfc5372e314d1219f03e64dde3ab495a5a25e
- affected 046f6fd5daefac7f5abdafb436b30f63bc7c602b – < 710866fc0a64eafcb8bacd91bcb1329eb7e5035f
- affected 046f6fd5daefac7f5abdafb436b30f63bc7c602b – < aa12ee1c1bd260943fd6ab556d8635811c332eeb
- affected 046f6fd5daefac7f5abdafb436b30f63bc7c602b – < ff57186b2cc39766672c4c0332323933e5faaa88
- affected 046f6fd5daefac7f5abdafb436b30f63bc7c602b – < 62d591dde4defb1333d202410609c4ddeae060b3
- affected 046f6fd5daefac7f5abdafb436b30f63bc7c602b – < 15de71d06a400f7fdc15bf377a2552b0ec437cf5
- affected 4.19
- unaffected < 4.19
- unaffected 5.4.297 – ≤ 5.4.*
- unaffected 5.10.241 – ≤ 5.10.*
- unaffected 5.15.190 – ≤ 5.15.*
- unaffected 6.1.149 – ≤ 6.1.*
- unaffected 6.6.103 – ≤ 6.6.*
- unaffected 6.12.44 – ≤ 6.12.*
- unaffected 6.16.4 – ≤ 6.16.*
- unaffected 6.17 – ≤ *
References
References11
- https://git.kernel.org/stable/c/7689ab22de36f8db19095f6bdf11f28cfde92f5c (opens in a new tab)
- https://git.kernel.org/stable/c/de04ddd2980b48caa8d7e24a7db2742917a8b280 (opens in a new tab)
- https://git.kernel.org/stable/c/0dacfc5372e314d1219f03e64dde3ab495a5a25e (opens in a new tab)
- https://git.kernel.org/stable/c/710866fc0a64eafcb8bacd91bcb1329eb7e5035f (opens in a new tab)
- https://git.kernel.org/stable/c/aa12ee1c1bd260943fd6ab556d8635811c332eeb (opens in a new tab)
- https://git.kernel.org/stable/c/ff57186b2cc39766672c4c0332323933e5faaa88 (opens in a new tab)
- https://git.kernel.org/stable/c/62d591dde4defb1333d202410609c4ddeae060b3 (opens in a new tab)
- https://git.kernel.org/stable/c/15de71d06a400f7fdc15bf377a2552b0ec437cf5 (opens in a new tab)
- https://lists.debian.org/debian-lts-announce/2025/10/msg00008.html (opens in a new tab)
- https://lists.debian.org/debian-lts-announce/2025/10/msg00007.html (opens in a new tab)
- https://cert-portal.siemens.com/productcert/html/ssa-032379.html (opens in a new tab)
Sources
The same CVE in the primary databases and aggregators, to check against.
- CVE.org record (opens in a new tab)
- CVE List JSON (GitHub) (opens in a new tab)
- NVD (opens in a new tab)
- FIRST EPSS (opens in a new tab)
- EUVD EUVD-2025-28946 (opens in a new tab)
- OSV.dev (opens in a new tab)
- GitHub Advisories (opens in a new tab)
- CIRCL Vulnerability-Lookup (opens in a new tab)
Badge for a README or a ticket
[](https://cveledger.app/cve/CVE-2025-39766)Record last updated .