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
What the EG score is made of (scorer v4.0: the three questions the 0–10 score mixes, published apart · methodology)
The EG score (5.5): severity, escalated by confirmed exploitation. This CVE's 5.5 is its impact severity (EG Severity), not escalated.
- EG Severity
- 5.5 MEDIUMCVSS-B, impact only: no KEV listing, EPSS or EG-KEV tier raises it.GitHub Security Advisory CVSS
- EG Likelihood
- 0.1% within 30 daysSource: FIRST EPSS (model v2026.06.15, score date 2026-10-24). FIRST's exploitation probability, not an EchelonGraph model.
- Confirmed exploitation
- None on record (CISA KEV, EG-KEV Tier 1)Reported apart from the likelihood: an observed fact, not a probability.
- EG Priority
- SSVC Track at medium mission impactTrack at low or medium mission impact; Track* at high (mission-essential systems).CISA BOD 26-04: 14 days if the affected system is publicly exposed; Fix on system upgrade if it is not.Each input and its source: the SSVC and BOD 26-04 blocks below.
SSVC (CISA's decision table, applied by EchelonGraph)Track at low or medium mission impact; Track* at high (mission-essential systems).
A fix is available. Apply it within your standard update timelines.
Exploitation none (no CISA value, KEV listing or exploit code on record) · Automatable no (CISA's BOD 26-04 default) · Technical impact total (CISA's BOD 26-04 default). EchelonGraph holds no SSVC assessment of this CVE from CISA: none of these inputs is from Vulnrichment. EchelonGraph applied CISA's decision table to them; CISA publishes SSVC inputs and the table, not a decision for each CVE. Mission impact is CISA's Mission & Well-being decision point, and only you can judge it. CISA's table makes it high when Mission Prevalence is Essential — the vulnerable component "directly provides capabilities that constitute at least one MEF for at least one entity" (MEF: mission essential function) — or when Public Well-Being Impact is Irreversible: "multiple fatalities are likely", the cyber-physical system "is likely lost or destroyed", "extreme or serious externalities" are imposed on other parties, or social systems such as elections or the financial grid "are destabilized and potentially collapse". CISA's decision table
BOD 26-04 (CISA's remediation timeline, Table 1)14 days if the affected system is publicly exposed; Fix on system upgrade if it is not.
In CISA KEV no (CISA's KEV catalog) · Automatable no (CISA's BOD 26-04 default) · Technical impact total (CISA's BOD 26-04 default). Where an input reads “CISA's BOD 26-04 default”, no one has published it for this CVE, and CISA's implementation guidance says: “If “Automatable” and “Technical Impact” information items about a CVE ID are not available and the CVE ID is not in the KEV Catalog, CISA will treat its values as “no” and “total,” respectively, until CISA or a third party provides metadata about the CVE ID. CISA will always provide the Vulnrichment data for a CVE ID listed in the KEV Catalog.” Whether your system is publicly exposed is yours to answer. BOD 26-04 binds US Federal Civilian Executive Branch agencies; for anyone else it is CISA's published timeline, a reference rather than an obligation. The directive · how EchelonGraph applies it