# CVE-2021-3818: Reliance on Cookies without Validation and Integrity Checking in getgrav/grav

> Attackers can bypass security controls in Grav CMS by exploiting cookies that lack validation and integrity checks.

- **Severity:** Medium 6.3 (`CVSS:3.0/AV:N/AC:L/PR:L/UI:N/S:U/C:L/I:L/A:L`)
- **Exploited in the wild:** Not known
- **Login needed:** Any signed-in user
- **Attackable:** Over the internet
- **Victim action needed:** Not needed
- **Fix available:** Yes
- **Published:** 27 Sep 2021
- **Updated:** 3 Aug 2024
- **Also known as:** GHSA-cg3q-59w7-rvc2

## What is CVE-2021-3818?

CVE-2021-3818 is a medium-severity vulnerability in Getgrav Grav, published on 27 Sep 2021. Any signed-in user can exploit it over the network, with no action from the victim.

### Official description

grav is vulnerable to Reliance on Cookies without Validation and Integrity Checking

Weakness: CWE-565 (Reliance on Cookies without Validation and Integrity Checking)

## Which versions are affected by CVE-2021-3818?

2 open source packages ship an affected version, including getgrav/grav. It affects 1 product.


| Package | Ecosystem | Affected | Fixed in |
| --- | --- | --- | --- |
| `getgrav/grav` | Packagist | All versions | 1.7.21 |
| `getgrav/grav` | Packagist | All versions | 1.7.21 |

Products: Getgrav Grav.

## How do I fix CVE-2021-3818?

Upgrade getgrav/grav to 1.7.21 or later.

## Is CVE-2021-3818 being exploited?

There is no known exploitation of CVE-2021-3818 in the wild and no public exploit code.

## Other vulnerabilities in Getgrav Grav

- [CVE-2023-34251](https://insights.sbomify.com/CVE-2023-34251/): Grav Server Side Template Injection vulnerability (critical 10.0)
- [CVE-2025-46199](https://insights.sbomify.com/CVE-2025-46199/): Cross-site scripting in n/a (critical 9.8)
- [CVE-2021-47812](https://insights.sbomify.com/CVE-2021-47812/): GravCMS 1.10.7 - Arbitrary YAML Write/Update (Unauthenticated) (2) (critical 9.3)
- [CVE-2025-66844](https://insights.sbomify.com/CVE-2025-66844/): Grav may be vulnerable to SSRF attack via Twig Templates (critical 9.1)
- [CVE-2022-2073](https://insights.sbomify.com/CVE-2022-2073/): Code Injection in getgrav/grav (critical 9.1)

## Fix prompt for AI coding agents

```text
Check this codebase for CVE-2021-3818 and fix it if it is affected.

What it is: CVE-2021-3818 is a medium-severity vulnerability in Getgrav Grav, published on 27 Sep 2021. Any signed-in user can exploit it over the network, with no action from the victim.
Exploitation: There is no known exploitation of CVE-2021-3818 in the wild and no public exploit code.

Affected packages and fixed versions:
- getgrav/grav (Packagist): affected all versions; fixed in 1.7.21
- getgrav/grav (Packagist): affected all versions; fixed in 1.7.21

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-2021-3818/ (Markdown: https://insights.sbomify.com/CVE-2021-3818/index.md)
```

## Sources

- CVE record: https://www.cve.org/CVERecord?id=CVE-2021-3818
- NVD: https://nvd.nist.gov/vuln/detail/CVE-2021-3818
- OSV: https://osv.dev/vulnerability/CVE-2021-3818

---
From sbomify Insights: https://insights.sbomify.com/CVE-2021-3818/
Summaries are generated and may contain mistakes; the official description above is the record.