# CVE-2021-30479: Missing authorization in n/a

> Guest users can access private message traffic in public streams due to a bug in the all_public_streams API feature.

- **Severity:** Medium 5.3 (`CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:L/I:N/A:N`)
- **Exploited in the wild:** Not known
- **Login needed:** Not needed
- **Attackable:** Over the internet
- **Victim action needed:** Not needed
- **Fix available:** No
- **Published:** 14 Apr 2021
- **Updated:** 3 Aug 2024
- **Also known as:** GHSA-r3hv-m3j5-mrfp

## What is CVE-2021-30479?

CVE-2021-30479 is a medium-severity missing authorization vulnerability in n/a, published on 14 Apr 2021. An attacker can exploit it over the internet without logging in, with no action from the victim.

### Official description

An issue was discovered in Zulip Server before 3.4. A bug in the implementation of the all_public_streams API feature resulted in guest users being able to receive message traffic to public streams that should have been only accessible to members of the organization.

Weakness: CWE-269 (Improper Privilege Management)

## Which versions are affected by CVE-2021-30479?

It affects 1 product.


Products: Zulip Zulip Server.

## How do I fix CVE-2021-30479?

No fix has been published for CVE-2021-30479 yet. Limit exposure of the affected software until one is available.

## Is CVE-2021-30479 being exploited?

There is no known exploitation of CVE-2021-30479 in the wild and no public exploit code.

## Other vulnerabilities in n/a

- [CVE-2019-18933](https://insights.sbomify.com/CVE-2019-18933/): Information disclosure in n/a (critical 9.8)
- [CVE-2020-15070](https://insights.sbomify.com/CVE-2020-15070/): Code injection in n/a (high 8.8)
- [CVE-2017-0910](https://insights.sbomify.com/CVE-2017-0910/): Missing authorization in Zulip Server (high 8.8)
- [CVE-2025-31478](https://insights.sbomify.com/CVE-2025-31478/): Zulip Authentication Backend Configuration Bypass (high 8.2)
- [CVE-2023-33186](https://insights.sbomify.com/CVE-2023-33186/): Cross-site scripting vulnerability in Zulip Server development branch via topic tooltip (high 8.2)

## Fix prompt for AI coding agents

```text
Check this codebase for CVE-2021-30479 and fix it if it is affected.

What it is: CVE-2021-30479 is a medium-severity missing authorization vulnerability in n/a, published on 14 Apr 2021. 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-2021-30479 in the wild and no public exploit code.

Affected product: n/a. 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-2021-30479/ (Markdown: https://insights.sbomify.com/CVE-2021-30479/index.md)
```

## Sources

- CVE record: https://www.cve.org/CVERecord?id=CVE-2021-30479
- NVD: https://nvd.nist.gov/vuln/detail/CVE-2021-30479
- OSV: https://osv.dev/vulnerability/CVE-2021-30479

---
From sbomify Insights: https://insights.sbomify.com/CVE-2021-30479/
Summaries are generated and may contain mistakes; the official description above is the record.