CVE-2025-67500: mastodon — Fix

Description

Mastodon is a free, open-source social network server based on ActivityPub. Versions 4.2.27 and prior, 4.3.0-beta.1 through 4.3.14, 4.4.0-beta.1 through 4.4.9, 4.5.0-beta.1 through 4.5.2 have discrepancies in error handling which allow checking whether a given status exists by sending a request with a non-English Accept-Language header. Using this behavior, an attacker who knows the identifier of a particular status they are not allowed to see can confirm whether this status exists or not. This cannot be used to learn the contents of the status or any other property besides its existence. This issue is fixed in versions 4.2.28, 4.3.15, 4.4.10 and 4.5.3.

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CVSS v3.1 Score

3.7

LOW

CVSS:3.1/AV:N/AC:H/PR:N/UI:N/S:U/C:L/I:N/A:N

Weakness Type (CWE)

CWE-204 CWE-204

Affected Products

Vendor	Product	Versions
joinmastodon	mastodon	< 4.2.28
joinmastodon	mastodon	4.3.0 — 4.3.15
joinmastodon	mastodon	4.4.0 — 4.4.10
joinmastodon	mastodon	4.5.0 — 4.5.3

References

Advisories & Patches

https://github.com/mastodon/mastodon/pull/37077/commits/9957d3218cb33fea6a44bb285e2ba4795a059e4f https://github.com/mastodon/mastodon/security/advisories/GHSA-gwhw-gcjx-72v8

Frequently Asked Questions

What is CVE-2025-67500? +

Mastodon is a free, open-source social network server based on ActivityPub. Versions 4.2.27 and prior, 4.3.0-beta.1 through 4.3.14, 4.4.0-beta.1 through 4.4.9, 4.5.0-beta.1 through 4.5.2 have discrepancies in error handling which allow checking whether a given status exists by sending a request with a non-English Accept-Language header. Using this behavior, an attacker who knows the identifier of a particular status they are not allowed to see can confirm whether this status exists or not. This cannot be used to learn the contents of the status or any other property besides its existence. This issue is fixed in versions 4.2.28, 4.3.15, 4.4.10 and 4.5.3. It has a CVSS v3.1 base score of 3.7 (LOW).

How severe is CVE-2025-67500? +

CVE-2025-67500 has a CVSS v3.1 score of 3.7 out of 10, rated LOW. This is a low-severity vulnerability with limited impact.

What products are affected by CVE-2025-67500? +

CVE-2025-67500 affects products from joinmastodon, specifically: mastodon. Check the affected products table above for specific version ranges.

How do I check if I'm vulnerable to CVE-2025-67500? +

You can use Secably's free Website Scanner to check your website for known vulnerabilities. For infrastructure scanning, use the Port Scanner to identify exposed services that may be affected. Check the vendor advisories linked above for specific patch and version information.

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