GHSA-C589-8XVR-7CM3
Vulnerability from github – Published: 2026-03-18 18:31 – Updated: 2026-05-29 21:31In 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
{
"affected": [],
"aliases": [
"CVE-2026-23266"
],
"database_specific": {
"cwe_ids": [
"CWE-369"
],
"github_reviewed": false,
"github_reviewed_at": null,
"nvd_published_at": "2026-03-18T18:16:25Z",
"severity": "MODERATE"
},
"details": "In the Linux kernel, the following vulnerability has been resolved:\n\nfbdev: rivafb: fix divide error in nv3_arb()\n\nA userspace program can trigger the RIVA NV3 arbitration code by calling\nthe FBIOPUT_VSCREENINFO ioctl on /dev/fb*. When doing so, the driver\nrecomputes FIFO arbitration parameters in nv3_arb(), using state-\u003emclk_khz\n(derived from the PRAMDAC MCLK PLL) as a divisor without validating it\nfirst.\n\nIn a normal setup, state-\u003emclk_khz is provided by the real hardware and is\nnon-zero. However, an attacker can construct a malicious or misconfigured\ndevice (e.g. a crafted/emulated PCI device) that exposes a bogus PLL\nconfiguration, causing state-\u003emclk_khz to become zero. Once\nnv3_get_param() calls nv3_arb(), the division by state-\u003emclk_khz in the gns\ncalculation causes a divide error and crashes the kernel.\n\nFix this by checking whether state-\u003emclk_khz is zero and bailing out before\ndoing the division.\n\nThe following log reveals it:\n\nrivafb: setting virtual Y resolution to 2184\ndivide error: 0000 [#1] PREEMPT SMP KASAN PTI\nCPU: 0 PID: 2187 Comm: syz-executor.0 Not tainted 5.18.0-rc1+ #1\nHardware name: QEMU Standard PC (i440FX + PIIX, 1996), BIOS rel-1.12.0-59-gc9ba5276e321-prebuilt.qemu.org 04/01/2014\nRIP: 0010:nv3_arb drivers/video/fbdev/riva/riva_hw.c:439 [inline]\nRIP: 0010:nv3_get_param+0x3ab/0x13b0 drivers/video/fbdev/riva/riva_hw.c:546\nCall Trace:\n nv3CalcArbitration.constprop.0+0x255/0x460 drivers/video/fbdev/riva/riva_hw.c:603\n nv3UpdateArbitrationSettings drivers/video/fbdev/riva/riva_hw.c:637 [inline]\n CalcStateExt+0x447/0x1b90 drivers/video/fbdev/riva/riva_hw.c:1246\n riva_load_video_mode+0x8a9/0xea0 drivers/video/fbdev/riva/fbdev.c:779\n rivafb_set_par+0xc0/0x5f0 drivers/video/fbdev/riva/fbdev.c:1196\n fb_set_var+0x604/0xeb0 drivers/video/fbdev/core/fbmem.c:1033\n do_fb_ioctl+0x234/0x670 drivers/video/fbdev/core/fbmem.c:1109\n fb_ioctl+0xdd/0x130 drivers/video/fbdev/core/fbmem.c:1188\n __x64_sys_ioctl+0x122/0x190 fs/ioctl.c:856",
"id": "GHSA-c589-8xvr-7cm3",
"modified": "2026-05-29T21:31:16Z",
"published": "2026-03-18T18:31:18Z",
"references": [
{
"type": "ADVISORY",
"url": "https://nvd.nist.gov/vuln/detail/CVE-2026-23266"
},
{
"type": "WEB",
"url": "https://git.kernel.org/stable/c/0209e21e3c372fa2da04c39214bec0b64e4eb5f4"
},
{
"type": "WEB",
"url": "https://git.kernel.org/stable/c/3e4cbd1d46c246dfa684c8e9d8c20ae0b960c50a"
},
{
"type": "WEB",
"url": "https://git.kernel.org/stable/c/526460a96c5443e2fc0fd231edd1f9c49d2de26b"
},
{
"type": "WEB",
"url": "https://git.kernel.org/stable/c/52916878db2b8e3769743a94484729f0844352df"
},
{
"type": "WEB",
"url": "https://git.kernel.org/stable/c/73f0391e92d404da68f7484e57c106c5e673dc7e"
},
{
"type": "WEB",
"url": "https://git.kernel.org/stable/c/78daf5984d96edec3b920c72a93bd6821b8710b7"
},
{
"type": "WEB",
"url": "https://git.kernel.org/stable/c/9efa0dc46270a8723c158c64afbcf1dead72b28c"
},
{
"type": "WEB",
"url": "https://git.kernel.org/stable/c/ec5a58f4fd581875593ea92a65485e1906a53c0f"
}
],
"schema_version": "1.4.0",
"severity": [
{
"score": "CVSS:3.1/AV:L/AC:L/PR:L/UI:N/S:U/C:N/I:N/A:H",
"type": "CVSS_V3"
}
]
}
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