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Linux CVE-2026-23266

| EUVDEUVD-2026-12907 MEDIUM
Divide By Zero (CWE-369)
2026-03-18 Linux
Denial Of Service Linux Red Hat Suse
5.5
CVSS 3.1 · NVD
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Severity by source

NVD PRIMARY
5.5 MEDIUM
AV:L/AC:L/PR:L/UI:N/S:U/C:N/I:N/A:H
SUSE
MEDIUM
qualitative

Primary rating from NVD.

CVSS VectorNVD

CVSS:3.1/AV:L/AC:L/PR:L/UI:N/S:U/C:N/I:N/A:H
Attack Vector
Local
Attack Complexity
Low
Privileges Required
Low
User Interaction
None
Scope
Unchanged
Confidentiality
None
Integrity
None
Availability
High

Lifecycle Timeline

5
CVSS changed
May 29, 2026 - 18:52 NVD
5.5 (MEDIUM)
Patch released
Mar 31, 2026 - 21:13 nvd
Patch available
EUVD ID Assigned
Mar 18, 2026 - 18:00 euvd
EUVD-2026-12907
Analysis Generated
Mar 18, 2026 - 18:00 vuln.today
CVE Published
Mar 18, 2026 - 17:44 nvd
N/A

DescriptionCVE.org

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

fbdev: rivafb: fix divide error in nv3_arb()

A userspace program can trigger the RIVA NV3 arbitration code by calling the FBIOPUT_VSCREENINFO ioctl on /dev/fb*. When doing so, the driver recomputes FIFO arbitration parameters in nv3_arb(), using state->mclk_khz (derived from the PRAMDAC MCLK PLL) as a divisor without validating it first.

In a normal setup, state->mclk_khz is provided by the real hardware and is non-zero. However, an attacker can construct a malicious or misconfigured device (e.g. a crafted/emulated PCI device) that exposes a bogus PLL configuration, causing state->mclk_khz to become zero. Once nv3_get_param() calls nv3_arb(), the division by state->mclk_khz in the gns calculation causes a divide error and crashes the kernel.

Fix this by checking whether state->mclk_khz is zero and bailing out before doing the division.

The following log reveals it:

rivafb: setting virtual Y resolution to 2184 divide error: 0000 [#1] PREEMPT SMP KASAN PTI CPU: 0 PID: 2187 Comm: syz-executor.0 Not tainted 5.18.0-rc1+ #1 Hardware name: QEMU Standard PC (i440FX + PIIX, 1996), BIOS rel-1.12.0-59-gc9ba5276e321-prebuilt.qemu.org 04/01/2014 RIP: 0010:nv3_arb drivers/video/fbdev/riva/riva_hw.c:439 [inline] RIP: 0010:nv3_get_param+0x3ab/0x13b0 drivers/video/fbdev/riva/riva_hw.c:546 Call Trace: nv3CalcArbitration.constprop.0+0x255/0x460 drivers/video/fbdev/riva/riva_hw.c:603 nv3UpdateArbitrationSettings drivers/video/fbdev/riva/riva_hw.c:637 [inline] CalcStateExt+0x447/0x1b90 drivers/video/fbdev/riva/riva_hw.c:1246 riva_load_video_mode+0x8a9/0xea0 drivers/video/fbdev/riva/fbdev.c:779 rivafb_set_par+0xc0/0x5f0 drivers/video/fbdev/riva/fbdev.c:1196 fb_set_var+0x604/0xeb0 drivers/video/fbdev/core/fbmem.c:1033 do_fb_ioctl+0x234/0x670 drivers/video/fbdev/core/fbmem.c:1109 fb_ioctl+0xdd/0x130 drivers/video/fbdev/core/fbmem.c:1188 __x64_sys_ioctl+0x122/0x190 fs/ioctl.c:856

AnalysisAI

A divide-by-zero vulnerability exists in the Linux kernel's rivafb framebuffer driver in the nv3_arb() function, which can be triggered by unprivileged userspace applications via the FBIOPUT_VSCREENINFO ioctl call on /dev/fb* devices. An attacker can crash the kernel by crafting a malicious or misconfigured PCI device that exposes a bogus PRAMDAC MCLK PLL configuration, causing the state->mclk_khz divisor to become zero. This is a Denial of Service vulnerability affecting the Linux kernel across multiple stable versions, with patches available in the kernel git repository.

Technical ContextAI

The vulnerability exists in the NVIDIA RIVA framebuffer driver (rivafb), specifically in the nv3_arb() arbitration parameter calculation function located in drivers/video/fbdev/riva/riva_hw.c. The driver computes FIFO arbitration parameters using the MCLK (memory clock) frequency derived from the PRAMDAC PLL configuration without validating that this value is non-zero before performing division operations. Under normal conditions with legitimate hardware, the MCLK frequency is provided by the actual graphics hardware and is non-zero. However, the driver does not validate this critical assumption, leading to a classic divide-by-zero error (CWE-369) when processing malicious device configurations. The vulnerable code path is triggered when a userspace process calls FBIOPUT_VSCREENINFO ioctl on any /dev/fb* device, which invokes the chain: fb_set_var() → rivafb_set_par() → riva_load_video_mode() → CalcStateExt() → nv3UpdateArbitrationSettings() → nv3_arb(). Affected Linux kernel versions are identified via CPE (cpe:2.3:a:linux:linux:*:*:*:*:*:*:*:*), spanning multiple stable release branches.

RemediationAI

Upgrade the Linux kernel to a patched version that includes the divide-by-zero check in nv3_arb(). Users should check their distribution's kernel security updates and apply patches from their vendor (e.g., RHEL, Ubuntu, Fedora kernel updates). The upstream kernel patches can be found in the stable kernel git repository at the commit hashes provided in the references section (ec5a58f4fd581875593ea92a65485e1906a53c0f and related). Until patching is possible, restrict access to /dev/fb* device files using filesystem permissions (chmod 600 or similar) and limit framebuffer access to trusted users only. For systems using legacy NVIDIA RIVA graphics hardware, consider disabling the rivafb driver if alternative framebuffer drivers are available. Container and VM environments should prioritize kernel updates and restrict guest access to emulated framebuffer devices. Distribution maintainers should apply the upstream patches to all supported stable kernel branches.

Same weakness CWE-369 – Divide By Zero

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Vendor StatusVendor

Debian

linux
Release Status Fixed Version Urgency
bullseye fixed 5.10.251-1 -
bullseye (security) fixed 5.10.251-1 -
bookworm fixed 6.1.164-1 -
bookworm (security) fixed 6.1.164-1 -
trixie fixed 6.12.74-1 -
trixie (security) fixed 6.12.74-2 -
forky fixed 6.19.6-2 -
sid fixed 6.19.8-1 -
(unstable) fixed 6.18.13-1 -

SUSE

Severity: Medium
Product Status
Container suse/sl-micro/6.0/base-os-container:2.1.3-7.145 Container suse/sl-micro/6.1/base-os-container:2.2.1-5.132 Affected
Container suse/sl-micro/6.0/kvm-os-container:2.1.3-6.162 Container suse/sl-micro/6.1/kvm-os-container:2.2.1-5.132 Affected
Container suse/sl-micro/6.0/rt-os-container:2.1.3-7.176 Container suse/sl-micro/6.1/rt-os-container:2.2.1-5.125 Affected
Image SLES-Azure-Basic Image SLES-EC2 Image SLES-Hardened-BYOS-Azure Image SLES-SAPCAL-Azure Affected
SUSE Linux Micro 6.2 Fixed

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CVE-2026-23266 vulnerability details – vuln.today
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