# CVE-2021-20786: Cross-site request forgery in GroupSession

> A CSRF vulnerability in GroupSession allows remote attackers to hijack administrator sessions via crafted URLs, requiring an upgrade to secure the application.

- **Severity:** Medium 4.3 (`CVSS:3.1/AV:N/AC:L/PR:N/UI:R/S:U/C:N/I:L/A:N`)
- **Exploited in the wild:** Not known
- **Login needed:** Not needed
- **Attackable:** Over the internet
- **Victim action needed:** A user has to click or open something
- **Fix available:** No
- **Published:** 28 Jul 2021
- **Updated:** 3 Aug 2024
- **Also known as:** GHSA-crxm-j8cj-fgm7

## What is CVE-2021-20786?

CVE-2021-20786 is a medium-severity vulnerability in Japan Total System Co.,Ltd. GroupSession, published on 28 Jul 2021. An attacker can exploit it over the internet without logging in, and only if a user opens a file or follows a link.

### Official description

Cross-site request forgery (CSRF) vulnerability in GroupSession (GroupSession Free edition from ver2.2.0 to the version prior to ver5.1.0, GroupSession byCloud from ver3.0.3 to the version prior to ver5.1.0, and GroupSession ZION from ver3.0.3 to the version prior to ver5.1.0) allows a remote attacker to hijack the authentication of administrators via a specially crafted URL.

Weakness: CWE-352 (Cross-Site Request Forgery)

## Which versions are affected by CVE-2021-20786?

It affects 3 products.


Products: Groupsession Groupsession, Groupsession Groupsession Bycloud, Groupsession Groupsession Zion.

## How do I fix CVE-2021-20786?

No fix has been published for CVE-2021-20786 yet. Limit exposure of the affected software until one is available.

## Is CVE-2021-20786 being exploited?

There is no known exploitation of CVE-2021-20786 in the wild and no public exploit code.

## Other vulnerabilities in Japan Total System Co.,Ltd. GroupSession

- [CVE-2021-20874](https://insights.sbomify.com/CVE-2021-20874/): Missing authorization in GroupSession Free edition, GroupSession byCloud, GroupSession ZION (high 7.5)
- [CVE-2025-61987](https://insights.sbomify.com/CVE-2025-61987/): Cross-site request forgery in GroupSession Free edition (medium 6.9)
- [CVE-2021-20876](https://insights.sbomify.com/CVE-2021-20876/): Path traversal in GroupSession Free edition, GroupSession byCloud, GroupSession ZION (medium 6.8)
- [CVE-2017-2165](https://insights.sbomify.com/CVE-2017-2165/): Information disclosure in GroupSession (medium 6.5)
- [CVE-2021-20875](https://insights.sbomify.com/CVE-2021-20875/): Open redirect in GroupSession Free edition, GroupSession byCloud, GroupSession ZION (medium 6.1)

## Fix prompt for AI coding agents

```text
Check this codebase for CVE-2021-20786 and fix it if it is affected.

What it is: CVE-2021-20786 is a medium-severity vulnerability in Japan Total System Co.,Ltd. GroupSession, published on 28 Jul 2021. An attacker can exploit it over the internet without logging in, and only if a user opens a file or follows a link.
Exploitation: There is no known exploitation of CVE-2021-20786 in the wild and no public exploit code.

Affected product: Japan Total System Co.,Ltd. GroupSession. 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-2021-20786/ (Markdown: https://insights.sbomify.com/CVE-2021-20786/index.md)
```

## Sources

- CVE record: https://www.cve.org/CVERecord?id=CVE-2021-20786
- NVD: https://nvd.nist.gov/vuln/detail/CVE-2021-20786
- OSV: https://osv.dev/vulnerability/CVE-2021-20786

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From sbomify Insights: https://insights.sbomify.com/CVE-2021-20786/
Summaries are generated and may contain mistakes; the official description above is the record.