# CVE-2026-47389: Mastodon: SSRF protection bypass on older Ruby versions

> Attackers can bypass SSRF protections on older Ruby versions to access internal network resources and cloud metadata endpoints.

- **Severity:** High 8.6 (`CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:C/C:H/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:** Yes
- **Published:** 24 Jun 2026
- **Updated:** 25 Jun 2026
- **Also known as:** BIT-mastodon-2026-47389, GHSA-xx55-4rrg-8xg6

## What is CVE-2026-47389?

CVE-2026-47389 is a high-severity server-side request forgery vulnerability in mastodon, published on 24 Jun 2026. An attacker can exploit it over the internet without logging in, with no action from the victim.

### Official description

Mastodon is a free, open-source social network server based on ActivityPub. Prior to 4.5.10, 4.4.17, and 4.3.23, when using Ruby versions older than 3.4, PrivateAddressCheck.private_address? returns false for IPv4-mapped IPv6 addresses (::ffff:a.b.c.d) corresponding to some private IPv4 addresses, depending on Ruby version, this can include loopback, RFC1918 private networks, and link-local space. An attacker who controls DNS for any domain can publish an AAAA record with such a mapped address; any outbound HTTP fetch Mastodon performs against that hostname then opens a real TCP connection to the underlying IPv4 address, including 127.0.0.1 and cloud-metadata endpoints such as 169.254.169.254. This vulnerability is fixed in 4.5.10, 4.4.17, and 4.3.23.

Weakness: CWE-918 (Server-Side Request Forgery), CWE-200 (Exposure of Sensitive Information to an Unauthorized Actor), CWE-184 (Incomplete List of Disallowed Inputs)

## Which versions are affected by CVE-2026-47389?

1 open source package ship an affected version, including mastodon.


| Package | Ecosystem | Affected | Fixed in |
| --- | --- | --- | --- |
| `mastodon` | Bitnami | From 4.5.0 | 4.5.10 |

## How do I fix CVE-2026-47389?

Upgrade mastodon to 4.5.10 or later.

## Is CVE-2026-47389 being exploited?

There is no known exploitation of CVE-2026-47389 in the wild and no public exploit code.

## Fix prompt for AI coding agents

```text
Check this codebase for CVE-2026-47389 and fix it if it is affected.

What it is: CVE-2026-47389 is a high-severity server-side request forgery vulnerability in mastodon, published on 24 Jun 2026. 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-2026-47389 in the wild and no public exploit code.

Affected packages and fixed versions:
- mastodon (Bitnami): affected from 4.5.0; fixed in 4.5.10

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-2026-47389/ (Markdown: https://insights.sbomify.com/CVE-2026-47389/index.md)
```

## Sources

- CVE record: https://www.cve.org/CVERecord?id=CVE-2026-47389
- NVD: https://nvd.nist.gov/vuln/detail/CVE-2026-47389
- OSV: https://osv.dev/vulnerability/CVE-2026-47389

---
From sbomify Insights: https://insights.sbomify.com/CVE-2026-47389/
Summaries are generated and may contain mistakes; the official description above is the record.