# CVE-2026-57852: Authentication Bypass via Null Short-Circuit in Grav CMS Scheduler Webhook Token Check

> Unauthenticated attackers can bypass webhook token validation to execute scheduled jobs, leading to remote code execution under the web server user.

- **Severity:** Medium 6.3 (`CVSS:4.0/AV:N/AC:H/AT:P/PR:N/UI:N/VC:L/VI:L/VA:L/SC:N/SI:N/SA:N`)
- **Exploited in the wild:** Not known
- **Login needed:** Not needed
- **Attackable:** Over the internet
- **Victim action needed:** Not needed
- **Fix available:** No
- **Published:** 20 Jul 2026
- **Updated:** 21 Jul 2026
- **Also known as:** GHSA-4p4x-7xpg-55gw

## What is CVE-2026-57852?

CVE-2026-57852 is a medium-severity authentication bypass vulnerability in Trilby Media Grav CMS scheduler-webhook plugin, published on 20 Jul 2026. An attacker can exploit it over the internet without logging in, with no action from the victim.

### Official description

Grav CMS scheduler-webhook plugin contains an authentication bypass vulnerability that allows unauthenticated remote attackers to trigger configured scheduled jobs by exploiting a short-circuit logic flaw in the webhook token validation. Attackers can send a single unauthenticated POST request to the scheduler webhook endpoint to execute all configured scheduled jobs or target a specific job, causing unintended execution of operator-defined commands under the web server process user.

Weakness: CWE-303 (Incorrect Implementation of Authentication Algorithm)

## Which versions are affected by CVE-2026-57852?


## How do I fix CVE-2026-57852?

No fix has been published for CVE-2026-57852 yet. Limit exposure of the affected software until one is available.

## Is CVE-2026-57852 being exploited?

There is no known exploitation of CVE-2026-57852 in the wild and no public exploit code.

## Fix prompt for AI coding agents

```text
Check this codebase for CVE-2026-57852 and fix it if it is affected.

What it is: CVE-2026-57852 is a medium-severity authentication bypass vulnerability in Trilby Media Grav CMS scheduler-webhook plugin, published on 20 Jul 2026. An attacker can exploit it over the internet without logging in, with no action from the victim.
Exploitation: There is no known exploitation of CVE-2026-57852 in the wild and no public exploit code.

Affected product: Trilby Media Grav CMS scheduler-webhook plugin. 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-2026-57852/ (Markdown: https://insights.sbomify.com/CVE-2026-57852/index.md)
```

## Sources

- CVE record: https://www.cve.org/CVERecord?id=CVE-2026-57852
- NVD: https://nvd.nist.gov/vuln/detail/CVE-2026-57852
- OSV: https://osv.dev/vulnerability/CVE-2026-57852

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From sbomify Insights: https://insights.sbomify.com/CVE-2026-57852/
Summaries are generated and may contain mistakes; the official description above is the record.