# CVE-2026-72313: drm/fb-helper: Only consider active CRTCs for vblank sync

> A flaw in the Linux kernel DRM fb-helper allows local attackers to cause a denial of service via vblank synchronization timeouts on inactive CRTCs.

- **Severity:** Not scored
- **Exploited in the wild:** Not known
- **Login needed:** Not needed
- **Attackable:** Local or same network only
- **Victim action needed:** Not needed
- **Fix available:** Yes
- **Published:** 15 Aug 2026
- **Updated:** 17 Aug 2026
- **Also known as:** DEBIAN-CVE-2026-72313, GHSA-c7fw-jq78-v3p5, UBUNTU-CVE-2026-72313

## What is CVE-2026-72313?

CVE-2026-72313 is a denial of service vulnerability in Linux, published on 15 Aug 2026. It can only be exploited from the same machine or local network, with no action from the victim.

### Official description

In the Linux kernel, the following vulnerability has been resolved:

drm/fb-helper: Only consider active CRTCs for vblank sync

Only synchronize fbdev output to the vblank of an active CRTC. Go over
the list of CRTCs and pick the first that matches. Fixes warnings as
the one shown below

[   77.201354] WARNING: drivers/gpu/drm/drm_vblank.c:1320 at drm_crtc_wait_one_vblank+0x194/0x1cc [drm], CPU#1: kworker/1:7/1867
[   77.201354] omapdrm omapdrm.0: [drm] vblank wait timed out on crtc 0

This currently happens if the fbdev output is not on CRTC 0.

Atomic and non-atomic drivers require distinct code paths. As for other
fbdev operations, implement both and select the correct one at runtime.

Not finding an active CRTC is not a bug. Do not wait in this case, but
flush the display update as before.

v4:
- avoid possible deadlocks with locking context (Sashiko)
v3:
- drop excessive state validation (Jani)
- acquire plane and CRTC mutices (Sashiko)
v2:
- move look-up code into separate helper
- support drivers with legacy modesetting
v1:
- see https://lore.kernel.org/dri-devel/1c9e0e24-9c4a-4259-8700-cf9e5fd60ca3@suse.de/

## Which versions are affected by CVE-2026-72313?


## How do I fix CVE-2026-72313?

Apply the vendor's patch.

## Is CVE-2026-72313 being exploited?

There is no known exploitation of CVE-2026-72313 in the wild and no public exploit code.

## Fix prompt for AI coding agents

```text
Check this codebase for CVE-2026-72313 and fix it if it is affected.

What it is: CVE-2026-72313 is a denial of service vulnerability in Linux, published on 15 Aug 2026. It can only be exploited from the same machine or local network, with no action from the victim.
Exploitation: There is no known exploitation of CVE-2026-72313 in the wild and no public exploit code.

Affected product: Linux. No package-level version data is available, so check the vendor advisory linked from the reference page.

Task:
1. Search the dependency manifests and lockfiles (for example package.json, package-lock.json, requirements.txt, poetry.lock, uv.lock, pom.xml, build.gradle, go.mod, Cargo.lock, Gemfile.lock) and any Dockerfiles for the affected packages, including transitive dependencies.
2. If an affected version is in use, upgrade it to the fixed version for its release line with the project's package manager, so the lockfile is regenerated. Prefer the smallest upgrade that fixes it.
3. If there is no fix, or the upgrade would break the build, do not guess: explain the risk and the safest workaround instead.
4. Run the tests and summarise what changed and why.
5. If nothing in the project is affected, say so and change nothing.

Reference: https://insights.sbomify.com/CVE-2026-72313/ (Markdown: https://insights.sbomify.com/CVE-2026-72313/index.md)
```

## Sources

- CVE record: https://www.cve.org/CVERecord?id=CVE-2026-72313
- NVD: https://nvd.nist.gov/vuln/detail/CVE-2026-72313
- OSV: https://osv.dev/vulnerability/CVE-2026-72313

---
From sbomify Insights: https://insights.sbomify.com/CVE-2026-72313/
Summaries are generated and may contain mistakes; the official description above is the record.