CVE-2026-90053

/// Technical description

In the Linux kernel, the following vulnerability has been resolved:

net/sched: sch_htb: limit htb_classify inner-class filter hops

htb_classify() follows each filter-selected inner class by switching

to cl->filter_list, but never bounds the number of hops. A filter on

an inner class can point back to itself or to another inner class that

points back, creating an infinite loop in the packet classification

path with the qdisc lock held and BH disabled — a soft lockup / panic

from a single packet.

Bound the traversal with a hop counter and drop the packet with a

rate-limited warning once the bound is exceeded. The counter is

incremented at the point the inner filter chain is picked up, after the

TC_ACT_* switch has consumed the classifier verdict, so a terminal

TC_ACT_QUEUED/STOLEN/TRAP on the last permitted chain still sets *qerr

to __NET_XMIT_STOLEN and the packet is not charged as a drop by this

qdisc or its parent.

The bound is TC_HTB_MAXDEPTH, taken from HTB's own parameters rath

/// Remediation

Check the references section for vendor advisories, patches, and mitigation guidance. If immediate patching is not possible, review the CVSS vector to understand the attack surface and apply compensating controls such as network segmentation or access restrictions.

/// References