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Linux Kernel CVE-2026-64121

| EUVDEUVD-2026-45806 HIGH
Out-of-bounds Read (CWE-125)
2026-07-19 Linux GHSA-478c-pq6v-xx69
Buffer Overflow Information Disclosure Linux Red Hat Suse
7.1
CVSS 3.1 · NVD
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Severity by source

NVD PRIMARY
7.1 HIGH
AV:L/AC:L/PR:L/UI:N/S:U/C:H/I:N/A:H
vuln.today AI
7.1 HIGH

Local vector confirmed; PR:L because unprivileged user namespaces allow low-privilege IFB device creation; no integrity impact from a read-only OOB.

3.1 AV:L/AC:L/PR:L/UI:N/S:U/C:H/I:N/A:H
4.0 AV:L/AC:L/AT:N/PR:L/UI:N/VC:H/VI:N/VA:H/SC:N/SI:N/SA:N
SUSE
HIGH
qualitative
Red Hat
5.5 MEDIUM
qualitative

Primary rating from NVD.

CVSS VectorNVD

Attack Vector
Local
Attack Complexity
Low
Privileges Required
Low
User Interaction
None
Scope
Unchanged
Confidentiality
High
Integrity
None
Availability
High

Lifecycle Timeline

5
Analysis Generated
Aug 13, 2026 - 15:23 vuln.today
CVSS changed
Aug 13, 2026 - 15:22 NVD
7.1 (HIGH)
Patch available
Jul 19, 2026 - 17:03 EUVD
CVE Published
Jul 19, 2026 - 15:40 nvd
HIGH 7.1
CVE Published
Jul 19, 2026 - 15:40 cve.org
UNKNOWN (no severity yet)

DescriptionNVD

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.

AnalysisAI

Slab out-of-bounds read in the Linux kernel IFB (Intermediate Functional Block) network driver exposes adjacent kernel memory and risks system instability when a local user with low privileges queries ethtool statistics on an asymmetrically configured IFB device. The root cause is a queue-count mismatch: ethtool stat callbacks size and walk per-queue data using real_num_rx_queues and real_num_tx_queues, while the underlying tx_private allocation is sized only to num_tx_queues - creating an over-read when RX queue count exceeds TX queue count. No public exploit has been identified at time of analysis, and EPSS sits at 0.17% (7th percentile), though patch availability across multiple stable branches confirms vendor acknowledgment and active remediation.

Technical ContextAI

The IFB driver (net/sched/ifb.c) is a Linux kernel pseudo-device used in traffic control (tc) to redirect ingress traffic for shaping. During device initialization, ifb_dev_init() allocates an array of ifb_q_private structs sized to dev->num_tx_queues via kzalloc_objs. Both per-queue RX stats (updated by ifb_xmit() via skb queue mapping) and TX stats (updated by ifb_ri_tasklet()) are stored in this single allocation, and ifb_stats64() correctly aggregates over dev->num_tx_queues. The defect is in the ethtool path: ifb_get_ethtool_stats() and related size/string functions reference dev->real_num_rx_queues and dev->real_num_tx_queues, which can exceed the allocation boundary when the device is created with asymmetric queue counts (e.g., numrxqueues 8 numtxqueues 1). The resulting read past the slab allocation constitutes CWE-125 (Out-of-bounds Read), confirmed by KASAN at v7.1-rc2. Affected products per CPE: cpe:2.3:a:linux:linux:*:*:*:*:*:*:*:* across multiple stable kernel branches from the introducing commit a21ee5b2fcb8d6d3973446c5039e966c4cfe40d1 onward.

RemediationAI

The primary fix is upgrading to a patched kernel version: Linux 6.1.175, 6.6.142, 6.12.92, 6.18.34, 7.0.11, or 7.1 (mainline), each containing the corrective commit that replaces real_num_rx_queues and real_num_tx_queues with num_tx_queues in the ethtool stats callbacks. Upstream fix commits are available at https://git.kernel.org/stable/c/6afdb8113cb007f9332f59a9b7fd45731b8a9de5, https://git.kernel.org/stable/c/5db89c99566fc4728cc92e941d8e1975711e24b5, https://git.kernel.org/stable/c/f8a5a76b4a683043c6eff2a060bcaa17f9316ad5, https://git.kernel.org/stable/c/2638e1773904d7aa8f24c6e7fda2ed7d69df6fa4, https://git.kernel.org/stable/c/16bd798cb6d8337d7c3eea1adc412f31b5181d5b, and https://git.kernel.org/stable/c/301a554e458e2f5ec47f2c336a7cb03b877f9fd6. Ubuntu users should apply packages per USN-8593-1. As a compensating control prior to patching, administrators can restrict creation of IFB devices by blocking unprivileged user namespaces (sysctl kernel.unprivileged_userns_clone=0 on supported distros), which prevents low-privilege users from creating network interfaces; note this will break sandboxed application runtimes (Flatpak, browsers using seccomp namespaces) that rely on unprivileged namespaces. Alternatively, restrict access to the ifb kernel module (blacklist ifb in /etc/modprobe.d/) if IFB-based traffic shaping is not in use - this has no impact unless tc redirect/ingress shaping is actively deployed.

Same weakness CWE-125 – Out-of-bounds Read

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Vendor StatusVendor

SUSE

Severity: Important
Product Status
SUSE Linux Enterprise Desktop 15 SP7 Affected
SUSE Linux Enterprise Desktop 15 SP7 Affected
SUSE Linux Enterprise High Availability Extension 15 SP7 Affected
SUSE Linux Enterprise High Availability Extension 15 SP7 Affected
SUSE Linux Enterprise High Availability Extension 16.0 Affected

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CVE-2026-64121 vulnerability details – vuln.today
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