CVE-2025-27399

What it is

Mastodon is a self-hosted, federated microblogging platform. In versions prior to 4.1.23, 4.2.16, and 4.3.4, when the visibility for domain blocks/reasons is set to "users" (localized English string: "To logged-in users"), users that are not yet approved can view the block reasons. Instance admins that do not want their domain blocks to be public are impacted. Versions 4.1.23, 4.2.16, and 4.3.4 fix the issue.

At a glance

Exploitability

Can be exploited over the network without logging in. Limited direct impact.

Exploit odds

0.4% chance of exploitation in the next 30 days (EPSS).

Fix

A patch, advisory or fixed version is referenced. Upgrade or apply it.

Timeline

1. 2025-02-27 18:15 UTC PublishedDisclosed publicly on CVE.org and NVD
2. 2026-06-17 09:03 UTC Last updatedMost recent change to the record

Why it ranks here

• Exploited in the wild: no, CISA does not list it.
• Exploit odds: 0.4% in the next 30 days (EPSS).
• Severity: 5.3 MEDIUM (CVSS).
• Fix: a patch or advisory is linked.

Details

Published

2025-02-27 18:15 UTC

Last modified

2026-06-17 09:03 UTC

Exploit probability

0.4% · EPSS, next 30 days

Weakness

CWE-200 · Information exposure

Record status

Analyzed

Affected

• Joinmastodon Mastodon < 4.1.23
• Joinmastodon Mastodon < 4.2.16
• Joinmastodon Mastodon < 4.3.4

Attack profile CVSS 3.1 · 5.3

Attack vector

Network

Complexity

Low

Privileges needed

None

User interaction

None

Scope

Unchanged

Confidentiality

Low

Integrity

None

Availability

None

Is it in your code?

Hand this to your coding agent. It searches your project for the affected products and checks versions. Nothing leaves your machine.

Read https://cve-list.com/agent/cve/CVE-2025-27399.md and follow it. Check whether this project is affected by CVE-2025-27399. Read only. Don't change anything and don't upload my code. Tell me yes, no or not sure, with the file as proof.

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