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Allocation of Resources Without Limits or Throttling Affecting kernel-64k-modules-core package, versions *

Severity

 Recommended
0.0
medium
0
10

Based on CentOS security rating.

Threat Intelligence

EPSS
0.17% (6th percentile)

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  • Snyk IDSNYK-CENTOS10-KERNEL64KMODULESCORE-20223262
  • published29 Sept 2026
  • disclosed25 Sept 2026
Report a new vulnerability Found a mistake?

Introduced: 25 Sep 2026

NewCVE-2026-98022  (opens in a new tab)
CWE-770  (opens in a new tab)

How to fix?

There is no fixed version for Centos:10 kernel-64k-modules-core.

NVD Description

Note: Versions mentioned in the description apply only to the upstream kernel-64k-modules-core package and not the kernel-64k-modules-core package as distributed by Centos. See How to fix? for Centos:10 relevant fixed versions and status.

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

net: cap tx_queue_len at S16_MAX to prevent oversized ring allocations

Several subsystems allocate ring buffers sized by dev->tx_queue_len with no upper bound. An unprivileged user (via unshare -Urn) can set a huge tx_queue_len and exhaust global memory with ring allocations:

  • pfifo_fast: pfifo_fast_init() and pfifo_fast_change_tx_queue_len() allocate 3 skb_array rings of tx_queue_len entries each.
  • tun: tun_queue_resize() and the queue-attach path resize ptr_rings to tx_queue_len on the NETDEV_CHANGE_TX_QUEUE_LEN notifier.
  • tap (macvtap/ipvtap): tap_queue_resize() and tap_init() resize/init ptr_rings to tx_queue_len on the same notifier.

netif_change_tx_queue_len() is the single entry point for IFLA_TXQLEN, sysfs, and the SIOCSIFTXQLEN ioctl. Cap new_len at S16_MAX (32767) there so the oversized value is rejected at set time. This takes effect whether the device is up or down, before dev->tx_queue_len is written, before any notifier fires, and before any ring is allocated. The "> S16_MAX" check also subsumes the previous unsigned-long truncation test, and a negative ifr_qlen from the ioctl lands far above the cap after conversion, so both old failure modes are covered by the one comparison.

tx_queue_len is ambigious: both a per-ring sizing multiplier and a default queue-length/limit knob for consumers that allocate nothing at set time (pfifo/bfifo/gred/plug/sfb limits, htb direct_qlen, qfq max_classes, teql). 32767 is chosen as the largest value NLA_POLICY_FULL_RANGE can express for the u32 IFLA_TXQLEN policy in patch 2/3 while staying a legitimate queue length on high-BDP paths; the ring-memory trade-off of a shared knob is disclosed below.

Conditions to recreate the bug:

  • CONFIG_NET_SCHED=y, CONFIG_VETH=y, CONFIG_USER_NS=y, CONFIG_NET_NS=y.
  • Unprivileged user in a fresh user+net namespace (unshare -Urn).
  • pfifo_fast: create veth pairs, set tx_queue_len to 500000, attach mq+pfifo_fast. ~28 iterations OOMs a 2GB guest.
  • tun: create 50 tun devices with IFF_MULTI_QUEUE, set tx_queue_len to 500000, open 8 queues each. ~1.6GB of ptr_ring allocations OOMs a 512MB guest.
  • tap: same as tun with IFF_TAP. ~960MB OOMs a 512MB guest.
  • On the fixed kernel the oversized tx_queue_len is rejected with -ERANGE at set time (all four paths: RTM_SETLINK, RTM_NEWLINK create, sysfs, ioctl - the latter two via this check, the former two via this check and the 2/3 parse policy respectively).

CVSS Base Scores

version 3.1