PT-2026-26126 · Linux · Linux

Published 2026-03-18 · Updated 2026-03-18 · CVE-2026-23266

Mitre

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

Related Identifiers

CVE-2026-23266

Affected Products

Linux

References · 9

• https://nvd.nist.gov/vuln/detail/CVE-2026-23266 · Security Note
• https://git.kernel.org/stable/c/ec5a58f4fd581875593ea92a65485e1906a53c0f · Note
• https://git.kernel.org/stable/c/526460a96c5443e2fc0fd231edd1f9c49d2de26b · Note
• https://git.kernel.org/stable/c/9efa0dc46270a8723c158c64afbcf1dead72b28c · Note
• https://git.kernel.org/stable/c/3e4cbd1d46c246dfa684c8e9d8c20ae0b960c50a · Note
• https://git.kernel.org/stable/c/78daf5984d96edec3b920c72a93bd6821b8710b7 · Note
• https://git.kernel.org/stable/c/52916878db2b8e3769743a94484729f0844352df · Note
• https://git.kernel.org/stable/c/73f0391e92d404da68f7484e57c106c5e673dc7e · Note
• https://git.kernel.org/stable/c/0209e21e3c372fa2da04c39214bec0b64e4eb5f4 · Note