CVE-2026-33869

Mastodon has a denial of service for quote authorization

MEDIUM
4.8
CVSS Score
Published: March 27, 2026 at 07:52 PM UTC
Updated: June 17, 2026 at 10:38 AM UTC
2 products affected across 2 vendorsMastodonMastodon

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Severity
MEDIUM4.8
Exploit prediction
EPSS 0.2%
SSVC
No known exploit

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.

Affected

Our own answer: ranges merged, affected separated from platform-only, with confidence and review flags.

4.4.0 ≤ v < 4.4.154.5.0 ≤ v < 4.5.8
v < 4.4.15v < 4.5.8
Affected range stops below 4.4.15, so it looks safe — our inference, not a vendor statement
Affected range stops below 4.5.8, so it looks safe — our inference, not a vendor statement

Remediation

No guide yet

No remediation guidance has been written for this CVE yet. What the record does show:

References (1)

x_refsource_CONFIRMVendor Advisory
Source: cverecord
https://github.com/mastodon/mastodon/security/advisories/GHSA-q4g8-82c5-9h33

SSVC — Action Prioritization

SSVCNo known exploitNot automatablePartial impact

SSVC signals action urgency (what to patch first), separate from CVSS which measures severity.

CVSS

4.8MEDIUMGitHub_M
Attack Vector
NETWORK
Complexity
HIGH
Privileges
NONE
User Interaction
NONE
Scope
UNCHANGED
Confidentiality
NONE
Integrity
LOW
Availability
LOW
Vector?

Quick Info

StatusANALYZED
CWE
CWE-863

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