Kernel rivafb: divide-by-zero in nv3_arb()
CVE-2026-23266 Published on March 18, 2026
fbdev: rivafb: fix divide error in nv3_arb()
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
Products Associated with CVE-2026-23266
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Affected Versions
Linux:- Version 1da177e4c3f41524e886b7f1b8a0c1fc7321cac2 and below ec5a58f4fd581875593ea92a65485e1906a53c0f is affected.
- Version 1da177e4c3f41524e886b7f1b8a0c1fc7321cac2 and below 52916878db2b8e3769743a94484729f0844352df is affected.
- Version 1da177e4c3f41524e886b7f1b8a0c1fc7321cac2 and below 526460a96c5443e2fc0fd231edd1f9c49d2de26b is affected.
- Version 1da177e4c3f41524e886b7f1b8a0c1fc7321cac2 and below 78daf5984d96edec3b920c72a93bd6821b8710b7 is affected.
- Version 1da177e4c3f41524e886b7f1b8a0c1fc7321cac2 and below 9efa0dc46270a8723c158c64afbcf1dead72b28c is affected.
- Version 1da177e4c3f41524e886b7f1b8a0c1fc7321cac2 and below 3e4cbd1d46c246dfa684c8e9d8c20ae0b960c50a is affected.
- Version 1da177e4c3f41524e886b7f1b8a0c1fc7321cac2 and below 73f0391e92d404da68f7484e57c106c5e673dc7e is affected.
- Version 1da177e4c3f41524e886b7f1b8a0c1fc7321cac2 and below 0209e21e3c372fa2da04c39214bec0b64e4eb5f4 is affected.
- Version 2.6.12 is affected.
- Before 2.6.12 is unaffected.
- Version 5.10.251, <= 5.10.* is unaffected.
- Version 5.15.201, <= 5.15.* is unaffected.
- Version 6.1.164, <= 6.1.* is unaffected.
- Version 6.6.127, <= 6.6.* is unaffected.
- Version 6.12.74, <= 6.12.* is unaffected.
- Version 6.18.13, <= 6.18.* is unaffected.
- Version 6.19.3, <= 6.19.* is unaffected.
- Version 7.0-rc1, <= * is unaffected.
Exploit Probability
EPSS (Exploit Prediction Scoring System) scores estimate the probability that a vulnerability will be exploited in the wild within the next 30 days. The percentile shows you how this score compares to all other vulnerabilities.