CVE-2026-64121
Received Received - Intake

Buffer Overflow in Linux Kernel Network Interface

Publication date: 2026-07-19

Last updated on: 2026-07-19

Assigner: kernel.org

Description
In the Linux kernel, the following vulnerability has been resolved: net: ifb: report ethtool stats over num_tx_queues ifb_dev_init() allocates dp->tx_private to dev->num_tx_queues entries via kzalloc_objs(*txp, dev->num_tx_queues). Both IFB per-queue RX and TX stats live in those entries: ifb_xmit() updates txp->rx_stats using the skb queue mapping, ifb_ri_tasklet() updates txp->tx_stats, and ifb_stats64() aggregates both over dev->num_tx_queues. The ethtool stats callbacks instead size and walk the per-queue stats with dev->real_num_rx_queues and dev->real_num_tx_queues. With an asymmetric device where the RX queue count exceeds the TX queue count, for example: ip link add name ifb10 numtxqueues 1 numrxqueues 8 type ifb ethtool -S ifb10 ifb_get_ethtool_stats() indexes past the tx_private allocation and copies adjacent slab data through ETHTOOL_GSTATS. Use dev->num_tx_queues consistently for the stats strings, the stats count, and the stats data walks. This reports one RX stats group and one TX stats group for each backing ifb_q_private entry, which is the queue set IFB can actually populate. Reproduced under UML+KASAN at v7.1-rc2: BUG: KASAN: slab-out-of-bounds in ifb_fill_stats_data+0x3c/0xae Read of size 8 at addr 0000000062dbd228 by task ethtool/36 ifb_fill_stats_data+0x3c/0xae ifb_get_ethtool_stats+0xc0/0x129 __dev_ethtool+0x1ca5/0x363c dev_ethtool+0x123/0x1b3 dev_ioctl+0x56c/0x744 sock_do_ioctl+0x15f/0x1b2 sock_ioctl+0x4d5/0x50a sys_ioctl+0xd8b/0xde9 With the patch applied, the same UML+KASAN repro is silent and ethtool -S ifb10 reports only the stats backed by the single allocated tx_private entry.

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Meta Information

Published
2026-07-19
Last Modified
2026-07-19
Generated
2026-07-20
AI Q&A
2026-07-19
EPSS Evaluated
N/A
NVD
CVE-2026-64121
EUVD
EUVD-2026-45806

Affected Vendors & Products

Showing 1 associated CPE
Vendor Product Version / Range
linux linux_kernel 7.1-rc2

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Exploitability

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CWE ID Description
CWE-UNKNOWN

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Executive Summary

This vulnerability in the Linux kernel involves an out-of-bounds read in the Intermediate Functional Block (IFB) device driver. It occurs when ethtool stats are reported for an IFB device with asymmetric RX and TX queue counts. The issue arises because the stats callbacks use inconsistent queue counts, leading to indexing past allocated memory and copying adjacent slab data.

Detection Guidance

This vulnerability can be detected by checking for slab-out-of-bounds errors when running ethtool -S on an IFB device with asymmetric RX/TX queues. Look for KASAN reports or crashes during ethtool operations on ifb interfaces.

Impact Analysis

This vulnerability can cause system crashes or instability due to memory corruption when running ethtool commands on affected IFB devices. It may also expose sensitive kernel memory to userspace, potentially leading to information disclosure or privilege escalation.

Compliance Impact

This vulnerability does not directly affect compliance with standards like GDPR or HIPAA as it is a Linux kernel memory corruption issue in the IFB network device driver. It may indirectly impact compliance if exploited to cause system instability or unauthorized data access, but no evidence suggests direct regulatory implications.

Mitigation Strategies

Apply the Linux kernel patch that ensures consistent use of dev->num_tx_queues for stats allocation and reporting. Avoid creating IFB devices with numrxqueues exceeding numtxqueues until patched.

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