Linux Distros Unpatched Vulnerability : CVE-2025-71066

critical Nessus Plugin ID 283647

Synopsis

The Linux/Unix host has one or more packages installed with a vulnerability that the vendor indicates will not be patched.

Description

The Linux/Unix host has one or more packages installed that are impacted by a vulnerability without a vendor supplied patch available.

- net/sched: ets: Always remove class from active list before deleting in ets_qdisc_change zdi- [email protected] says: The vulnerability is a race condition between `ets_qdisc_dequeue` and `ets_qdisc_change`. It leads to UAF on `struct Qdisc` object. Attacker requires the capability to create new user and network namespace in order to trigger the bug. See my additional commentary at the end of the analysis. Analysis: static int ets_qdisc_change(struct Qdisc *sch, struct nlattr *opt, struct netlink_ext_ack *extack) { ... // (1) this lock is preventing .change handler (`ets_qdisc_change`) //to race with .dequeue handler (`ets_qdisc_dequeue`) sch_tree_lock(sch); for (i = nbands; i < oldbands; i++) { if (i >= q->nstrict && q->classes[i].qdisc->q.qlen) list_del_init(&q->classes[i].alist);
qdisc_purge_queue(q->classes[i].qdisc); } WRITE_ONCE(q->nbands, nbands); for (i = nstrict; i < q->nstrict;
i++) { if (q->classes[i].qdisc->q.qlen) { // (2) the class is added to the q->active list_add_tail(&q->classes[i].alist, &q->active); q->classes[i].deficit = quanta[i]; } } WRITE_ONCE(q->nstrict, nstrict); memcpy(q->prio2band, priomap, sizeof(priomap)); for (i = 0; i < q->nbands; i++) WRITE_ONCE(q->classes[i].quantum, quanta[i]); for (i = oldbands; i < q->nbands; i++) { q->classes[i].qdisc = queues[i]; if (q->classes[i].qdisc != &noop_qdisc) qdisc_hash_add(q->classes[i].qdisc, true); } // (3) the qdisc is unlocked, now dequeue can be called in parallel // to the rest of .change handler sch_tree_unlock(sch); ets_offload_change(sch); for (i = q->nbands; i < oldbands; i++) { // (4) we're reducing the refcount for our class's qdisc and // freeing it qdisc_put(q->classes[i].qdisc); // (5) If we call .dequeue between (4) and (5), we will have // a strong UAF and we can control RIP q->classes[i].qdisc = NULL; WRITE_ONCE(q->classes[i].quantum, 0);
q->classes[i].deficit = 0; gnet_stats_basic_sync_init(&q->classes[i].bstats);
memset(&q->classes[i].qstats, 0, sizeof(q->classes[i].qstats)); } return 0; } Comment: This happens because some of the classes have their qdiscs assigned to NULL, but remain in the active list. This commit fixes this issue by always removing the class from the active list before deleting and freeing its associated qdisc Reproducer Steps (trimmed version of what was sent by [email protected]) ``` DEV=${DEV:-lo} ROOT_HANDLE=${ROOT_HANDLE:-1:} BAND2_HANDLE=${BAND2_HANDLE:-20:} # child under 1:2 PING_BYTES=${PING_BYTES:-48} PING_COUNT=${PING_COUNT:-200000} PING_DST=${PING_DST:-127.0.0.1} SLOW_TBF_RATE=${SLOW_TBF_RATE:-8bit} SLOW_TBF_BURST=${SLOW_TBF_BURST:-100b} SLOW_TBF_LAT=${SLOW_TBF_LAT:-1s} cleanup() { tc qdisc del dev $DEV root 2>/dev/null } trap cleanup EXIT ip link set $DEV up tc qdisc del dev $DEV root 2>/dev/null || true tc qdisc add dev $DEV root handle $ROOT_HANDLE ets bands 2 strict 2 tc qdisc add dev $DEV parent 1:2 handle $BAND2_HANDLE \ tbf rate $SLOW_TBF_RATE burst $SLOW_TBF_BURST latency $SLOW_TBF_LAT tc filter add dev $DEV parent 1:
protocol all prio 1 u32 match u32 0 0 flowid 1:2 tc -s qdisc ls dev $DEV ping -I $DEV -f -c $PING_COUNT -s $PING_BYTES -W 0.001 $PING_DST \ >/dev/null 2>&1 & tc qdisc change dev $DEV root handle $ROOT_HANDLE ets bands 2 strict 0 tc qdisc change dev $DEV root handle $ROOT_HANDLE ets bands 2 strict 2 tc -s qdisc ls dev $DEV tc qdisc del dev $DEV parent ---truncated--- (CVE-2025-71066)

Note that Nessus relies on the presence of the package as reported by the vendor.

Solution

There is no known solution at this time.

Plugin Details

Severity: Critical

ID: 283647

File Name: unpatched_CVE_2025_71066.nasl

Version: 1.1

Type: local

Agent: unix

Family: Misc.

Published: 1/13/2026

Updated: 1/13/2026

Supported Sensors: Nessus Agent, Nessus

Risk Information

VPR

Risk Factor: Medium

Score: 6.0

CVSS v2

Risk Factor: High

Base Score: 7.5

Temporal Score: 6.4

Vector: CVSS2#AV:N/AC:L/Au:N/C:P/I:P/A:P

CVSS Score Source: CVE-2025-71066

CVSS v3

Risk Factor: Critical

Base Score: 9.8

Temporal Score: 9

Vector: CVSS:3.0/AV:N/AC:L/PR:N/UI:N/S:U/C:H/I:H/A:H

Temporal Vector: CVSS:3.0/E:U/RL:U/RC:C

Vulnerability Information

CPE: cpe:/o:debian:debian_linux:11.0, p-cpe:/a:debian:debian_linux:linux, cpe:/o:debian:debian_linux:14.0, cpe:/o:debian:debian_linux:12.0, cpe:/o:debian:debian_linux:13.0

Required KB Items: Host/local_checks_enabled, Host/cpu, global_settings/vendor_unpatched, Host/OS/identifier

Exploit Ease: No known exploits are available

Vulnerability Publication Date: 1/13/2026

Reference Information

CVE: CVE-2025-71066

Detections

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