CVE-2025-39766

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.

PUBLISHED Reserved 2025-04-16 | Published 2025-09-11 | Updated 2025-09-29 | Assigner Linux

Product status

References

git.kernel.org/...c/7689ab22de36f8db19095f6bdf11f28cfde92f5c

git.kernel.org/...c/de04ddd2980b48caa8d7e24a7db2742917a8b280

git.kernel.org/...c/0dacfc5372e314d1219f03e64dde3ab495a5a25e

git.kernel.org/...c/710866fc0a64eafcb8bacd91bcb1329eb7e5035f

git.kernel.org/...c/aa12ee1c1bd260943fd6ab556d8635811c332eeb

git.kernel.org/...c/ff57186b2cc39766672c4c0332323933e5faaa88

git.kernel.org/...c/62d591dde4defb1333d202410609c4ddeae060b3

git.kernel.org/...c/15de71d06a400f7fdc15bf377a2552b0ec437cf5

cve.org (CVE-2025-39766)

nvd.nist.gov (CVE-2025-39766)

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