Medium severity · published Mar 27, 2026
CVE-2026-33869
Mastodon has a denial of service for quote authorization
4.8
CVSS
0.2%
EPSS
No
On KEV
Description
Mastodon is a free, open-source social network server based on ActivityPub. In versions on the 4.5.x branch prior to 4.5.8 and on the 4.4.x branch prior to 4.4.15, an attacker that knows of a quote before it has reached a server can prevent it from being correctly processed on that server. The vulnerability has been patched in Mastodon 4.5.8 and 4.4.15. Mastodon 4.3 and earlier are not affected because they do not support quotes.
CVSS vector
CVSS:3.1/AV:N/AC:H/PR:N/UI:N/S:U/C:N/I:L/A:L
Attack vector
Network
Complexity
High
Privileges
None
User interaction
None
Confidentiality
None
Integrity
Low
Availability
Low
Scope
Unchanged
Exploitation
Is it being used?
Exploit prediction (EPSS)0.2% · higher than 7% of CVEs
Exploited in the wildNo evidence yet
CISA KEVNot listed
Ransomware campaign useNot known
Affected products
Which versions
MA
mastodon · mastodon
>= 4.5.0, < 4.5.8; >= 4.4.0, < 4.4.15 · source: vendor, NVD
References
NVD
https://nvd.nist.gov/vuln/detail/CVE-2026-33869
CVE.org
https://www.cve.org/CVERecord?id=CVE-2026-33869
Vendor Advisory
https://github.com/mastodon/mastodon/security/advisories/GHSA-q4g8-82c5-9h33
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