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Vulnerabilities

Vulnerability · CVE-2026-33869

Mastodon is a free, open-source social network server based on ActivityPub.

Published Mar 27, 2026 · catalog updated Jun 17, 2026 · Mastodon is a free,

Check if you run it

No confirmed exploitation is on record for CVE-2026-33869. EPSS is 0.27%. Act only if a listed version of Mastodon is a free, is installed.

Gaps on this record

  • The stored product name is a package slug. The name on this page is taken from the title (Mastodon is a free,).
  • No vendor fix or required action is stored. Compare the linked advisory before you change production.
Severity
Medium4.8
Known exploitation
Not in CISA/VulnCheck KEV
EPSS
0.27%
Remediation
Version ranges on file
Affected products
cpe joinmastodon/mastodon · stated mastodon

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.

Are you affected?

Enter the version you run. The result uses only the ranges stored on this record.

The check returns affected, not affected, or incomplete. It does not guess a version that is missing from the record.

  • cpe joinmastodon/mastodonversion unspecified
  • stated mastodon<= 4.3

How to fix CVE-2026-33869

What to do

Three questions, each answered from this record only. Confirm the vendor advisory before you patch.

Should you patch?

No confirmed exploitation is on record for CVE-2026-33869. EPSS is 0.27%. Act only if a listed version of Mastodon is a free, is installed.

Which versions are affected?

Compare what you have installed with <= 4.3. Compare the installed version with the linked vendor advisory before you change production.

What should an analyst verify?

CWE-863: Incorrect Authorization. EPSS 0.27%. There is no CISA KEV listing. No Exploit-DB or Metasploit reference is linked. Use the source links for the original advisory.

Code

The project this record applies to. Exploit listings stay in References.

Timeline

Detection, updates, and resolution for this record.

  1. Mar 27, 2026 · NIST NVD

    Detected

    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 be

  2. Jun 17, 2026 · NIST NVD

    Updated

    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 be

Sources

  • CVE.orgVulnerability recordCVE-2026-33869

    Official CVE identifier

    cve.org
  • FIRST EPSSExploitation probabilityCVE-2026-33869

    30-day exploitation probability 0.3%

    first.org
  • NIST NVDVulnerability recordCVE-2026-33869

    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 th

    nvd.nist.gov

References

Freshness

Last verified in this catalog Oct 18, 2026. Significant claims (KEV, EPSS, CVSS, affected ranges) come from the source rows above — open the original publisher for the authoritative advisory.