VulnerabilityPublished 2 Mar 2026Updated 10 Sep 2026

CVE-2026-27468: Mastodon may allow unconfirmed FASP to make subscriptions

Affects mastodonSource GCVE Database

Not known to be exploited : upgrade to 4.5.7 or 4.4.14 soon.

Data as of 26 Oct 2026, 10:12 UTC

Severity

High

Rated by Threat Radar · No CVSS score from NVD or the CNA

EPSS: 0.2% chance of exploitation in 30 days – higher than 20% of CVEsExploit Prediction Scoring System: the likelihood attackers will use this flaw soon.
Patch: Available – fixed in 4.5.7, 4.4.14

Exploitation evidence

Disclosed: evidence found.
CVE published 2 Mar 2026
Detectable: no evidence on record.
No public nuclei template indexed
Weaponised: no evidence on record.
No public exploit code indexed in Metasploit or Exploit-DB
Exploited in the wildExploited: no evidence on record.
Not in CISA KEV and no source reports exploitation
Observed by OffSeq MirageSeen by Mirage: no evidence on record.
No attack traffic recorded by OffSeq Mirage sensors

A missing step is not evidence of safety. Sources: cve.org (opens in a new tab), the Metasploit, Exploit-DB and nuclei-templates index as of 26 Oct 2026.

Disclosed: The CVE record is public on cve.org. Its publication is t = 0.
Detectable: A public nuclei template can find exposed instances, for defenders and attackers alike.
Weaponised: Public exploit code exists in Metasploit or Exploit-DB, or CISA SSVC or the CVSS exploit maturity reports a public proof of concept.
Exploited in the wild: CISA KEV lists it, CISA SSVC rates exploitation active, or a source reports attacks.
Observed by OffSeq Mirage: OffSeq Mirage honeypot sensors recorded attack traffic for this CVE, or found exposed hosts without attack traffic.

Moments are spaced evenly, not to scale; a dashed line marks a gap of six months or more. Deltas count from t = 0. Sources that give only a date (CISA KEV, Exploit-DB, or a time of exactly 00:00Z) read “same day” rather than hours. Metasploit modules carry the flaw’s disclosure date, not their release date, and nuclei templates carry no date, so both appear above but not on the timeline.

What to do

Upgrade mastodon to 4.5.7 or 4.4.14.

Patches and advisories

github.com/mastodon/mastodon/commit/6ba6285a73c3a8b281123814d45f534e3bcebb96 (opens in a new tab)

Affected software

Product	Affected	Fixed in
Bitnamimastodon`pkg:bitnami/mastodon`Other threats	Affected >=4.4.0 <4.4.14 >=4.5.0 <4.5.7	Fixed in 4.4.14 4.5.7

Check your own hosts for these packages with threat-finder (opens in a new tab), our free open-source scanner.

AI-suggested

A fix is available in Mastodon versions 4.4.14 and 4.5.7. Administrators actively testing the experimental 'fasp' feature should update to these versions to remediate the vulnerability. Servers not using the 'fasp' experimental feature are not affected and require no action related to this issue.

Description

Mastodon versions 4.4.0 through 4.4.13 and 4.5.0 through 4.5.6 have a vulnerability affecting the experimental FASP feature. This flaw allows unconfirmed FASP registrations to make subscriptions and request content backfill without administrator approval. The issue only impacts servers that have enabled the experimental 'fasp' feature via the EXPERIMENTAL_FEATURES environment variable. Exploitation can lead to minor information leaks of publicly available URIs and, if repeated, can cause denial-of-service conditions by overloading the sidekiq worker handling the 'fasp' queue. The vulnerability is fixed in Mastodon versions 4.4.14 and 4.5.7. Servers not using the experimental feature are not affected.

Impact

An attacker controlling an unapproved FASP can subscribe to events and request content backfill without authorization. Initially, this leads to minor information leakage of URIs that are already publicly accessible. However, repeated exploitation can cause denial-of-service by overloading the sidekiq worker responsible for processing the 'fasp' queue, potentially degrading server performance or availability. Servers not opting into the experimental 'fasp' feature are unaffected.

Summary

Mastodon is an open-source social network server implementing ActivityPub. The vulnerability (CVE-2026-27468) exists in the experimental FASP feature, which requires manual administrator approval for registrations. In affected versions (>=4.4.0 <4.4.14 and >=4.5.0 <4.5.7), the system failed to properly verify approval status before allowing FASP entities to subscribe to account or content lifecycle events and request content backfill. This flaw enables unapproved FASP entities to perform these actions, resulting in minor information disclosure of publicly accessible URIs and potential denial-of-service by overwhelming the sidekiq worker queue. The issue is resolved in versions 4.4.14 and 4.5.7. Only servers with the experimental 'fasp' feature enabled are vulnerable.

References

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