# CVE-2026-75833: Grav API Plugin Open Redirect via Backslash Bypass

> Attackers can redirect authenticated users to malicious sites via a backslash bypass in the Grav API plugin's OAuth return URL validation.

- **Severity:** High 8.6 (`CVSS:4.0/AV:N/AC:L/AT:N/PR:L/UI:P/VC:H/VI:H/VA:H/SC:N/SI:N/SA:N`)
- **Exploited in the wild:** Not known
- **Login needed:** Any signed-in user
- **Attackable:** Over the internet
- **Victim action needed:** A user has to click or open something
- **Fix available:** No
- **Published:** 18 Aug 2026
- **Updated:** 18 Aug 2026
- **Also known as:** GHSA-chr5-7vjc-3p97

## What is CVE-2026-75833?

CVE-2026-75833 is a high-severity vulnerability in getgrav grav, published on 18 Aug 2026. Any signed-in user can exploit it over the network, and only if a user opens a file or follows a link.

### Official description

The Grav API plugin (getgrav/grav-plugin-api, bundled with Grav 2.0's admin-next/API stack) before version 1.0.14 contains an open redirect weakness in SsoController::sanitizeReturnTo(). The function rejects a literal '//' prefix but does not account for browsers normalizing backslashes to slashes in special (http/https) schemes, so a returnTo value such as '/\evil.com' passes the guard and is later resolved by the browser as the protocol-relative URL '//evil.com'. Following a legitimate OAuth login flow, an attacker-supplied returnTo parameter could redirect an authenticated victim to an attacker-controlled site for post-login phishing. Full browser-side exploitability depends on the admin-next SPA's client-side oauth-callback handler and was not independently verified by the reporter.

Weakness: CWE-601 (URL Redirection to Untrusted Site)

## Which versions are affected by CVE-2026-75833?


## How do I fix CVE-2026-75833?

No fix has been published for CVE-2026-75833 yet. Limit exposure of the affected software until one is available.

## Is CVE-2026-75833 being exploited?

It is not confirmed as exploited in the wild, but public exploit code for CVE-2026-75833 exists.

## Fix prompt for AI coding agents

```text
Check this codebase for CVE-2026-75833 and fix it if it is affected.

What it is: CVE-2026-75833 is a high-severity vulnerability in getgrav grav, published on 18 Aug 2026. Any signed-in user can exploit it over the network, and only if a user opens a file or follows a link.
Exploitation: It is not confirmed as exploited in the wild, but public exploit code for CVE-2026-75833 exists.

Affected product: getgrav grav. 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-2026-75833/ (Markdown: https://insights.sbomify.com/CVE-2026-75833/index.md)
```

## Sources

- CVE record: https://www.cve.org/CVERecord?id=CVE-2026-75833
- NVD: https://nvd.nist.gov/vuln/detail/CVE-2026-75833
- OSV: https://osv.dev/vulnerability/CVE-2026-75833

---
From sbomify Insights: https://insights.sbomify.com/CVE-2026-75833/
Summaries are generated and may contain mistakes; the official description above is the record.