CVE-2026-25540

MEDIUM EPSS 31.2%

Published Feb 4, 20264mo ago · Modified Jun 17, 20261w ago

6.5 CVSS 3.1

Medium

Published Feb 4, 2026 4mo ago

Last Modified Jun 17, 2026 1w ago

Description

Mastodon is a free, open-source social network server based on ActivityPub. Prior to versions 4.3.19, 4.4.13, 4.5.6, Mastodon is vulnerable to web cache poisoning via `Rails.cache. When AUTHORIZED_FETCH is enabled, the ActivityPub endpoints for pinned posts and featured hashtags have contents that depend on the account that signed the HTTP request. However, these contents are stored in an internal cache and reused with no regards to the signing actor. As a result, an empty response generated for a blocked user account may be served to requests from legitimate non-blocked actors, or conversely, content intended for non-blocked actors may be returned to blocked actors. This issue has been patched in versions 4.3.19, 4.4.13, 4.5.6.

CVSS Details

Base Score

6.5

Exploitability

3.9

Impact

2.5

Vector string

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

Attack Vector Network

Attack Complexity Low

Privileges Required None

User Interaction None

Scope Unchanged

Confidentiality Low

Integrity None

Availability Low

Threat Intelligence

EPSS Exploit Probability

31.2% percentile

Exploit & Patch Status

No Known Exploit

No Patch Available

Weaknesses 1

CWE-524

Affected Products 3

Vendor	Product	Version	Range
joinmastodon	mastodon	*	<4.3.19
joinmastodon	mastodon	*	≥4.4.0 – <4.4.13
joinmastodon	mastodon	*	≥4.5.0 – <4.5.6

References 1

github.com https://github.com/mastodon/mastodon/security/advisories/GHSA-ccpr-m53r-mfwr

Vendor Advisory

Remediation

No remediation data recorded yet

Check vendor advisories and the NVD entry for patch availability.