CVE-2026-33869

low-risk
Published 2026-03-27

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.

Do I need to act?

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0.05% chance of exploitation
EPSS score — low exploit probability
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Not on CISA KEV list
No confirmed active exploitation reported to CISA
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Patch status unknown
Check vendor advisories for fix availability and mitigation guidance
4
CVSS 4.8/10 Medium
NETWORK / HIGH complexity

Affected Products (1)

Affected Vendors

Joinmastodon

References (1)

Vendor Advisory https://github.com/mastodon/mastodon/security/advisories/GHSA-q4g8-82c5-9h33
20
/ 100
low-risk
Severity 15/34 · Moderate
Exploitability 0/34 · Minimal
Exposure 5/34 · Minimal