# CVE-2026-27737: BigBlueButton has Stored XSS in bbb-playback replay

> Attackers can inject malicious scripts into public chat messages that execute when users replay recordings, potentially compromising viewer accounts.

- **Severity:** Medium 6.5 (`CVSS:3.1/AV:N/AC:L/PR:L/UI:N/S:U/C:N/I:H/A:N`)
- **Exploited in the wild:** Not known
- **Login needed:** Any signed-in user
- **Attackable:** Over the internet
- **Victim action needed:** Not needed
- **Fix available:** No
- **Published:** 18 May 2026
- **Updated:** 19 May 2026
- **Also known as:** GHSA-8vv7-vj94-q2pv

## What is CVE-2026-27737?

CVE-2026-27737 is a medium-severity cross-site scripting vulnerability in bigbluebutton bbb-playback, published on 18 May 2026. Any signed-in user can exploit it over the network, with no action from the victim.

### Official description

BigBlueButton is an open-source virtual classroom. In versions prior to 3.0.19, the recording playback (presentation format) was not sanitizing user's input in public chat. This allowed for a malicious actor to craft and carry out a targeted XSS attack, activated on anyone replaying the recording. This issue has been fixed 3.0.19.

Weakness: CWE-79 (Improper Neutralization of Input During Web Page Generation)

## Which versions are affected by CVE-2026-27737?


## How do I fix CVE-2026-27737?

No fix has been published for CVE-2026-27737 yet. Limit exposure of the affected software until one is available.

## Is CVE-2026-27737 being exploited?

There is no known exploitation of CVE-2026-27737 in the wild and no public exploit code.

## Fix prompt for AI coding agents

```text
Check this codebase for CVE-2026-27737 and fix it if it is affected.

What it is: CVE-2026-27737 is a medium-severity cross-site scripting vulnerability in bigbluebutton bbb-playback, published on 18 May 2026. Any signed-in user can exploit it over the network, with no action from the victim.
Exploitation: There is no known exploitation of CVE-2026-27737 in the wild and no public exploit code.

Affected product: bigbluebutton bbb-playback. 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-2026-27737/ (Markdown: https://insights.sbomify.com/CVE-2026-27737/index.md)
```

## Sources

- CVE record: https://www.cve.org/CVERecord?id=CVE-2026-27737
- NVD: https://nvd.nist.gov/vuln/detail/CVE-2026-27737
- OSV: https://osv.dev/vulnerability/CVE-2026-27737

---
From sbomify Insights: https://insights.sbomify.com/CVE-2026-27737/
Summaries are generated and may contain mistakes; the official description above is the record.