How severe is CVE-2026-22246?

CVE-2026-22246 has a CVSS 3.x base score of 6.5, rated medium severity. It is exploitable over network with low attack complexity, requires low privileges and no user interaction. Impact on confidentiality is high, integrity none, and availability none.

Is CVE-2026-22246 being actively exploited?

It is not currently listed in CISA's KEV catalog. Its EPSS exploit-prediction score is 0% (14th percentile), an estimate of the probability of exploitation in the next 30 days.

What products are affected by CVE-2026-22246?

CVE-2026-22246 affects Joinmastodon Mastodon. See the affected-products list for the exact vulnerable versions.

How do I fix CVE-2026-22246?

Review the linked vendor and NVD advisories for patched versions and mitigations, then upgrade or apply the recommended workaround.

Does CVE-2026-22246 have an EU (EUVD) identifier?

Yes. CVE-2026-22246 is tracked in the ENISA EU Vulnerability Database (EUVD) as EUVD-2026-1675.

When was CVE-2026-22246 published?

CVE-2026-22246 was published on 2026-01-08 and last updated on 2026-06-17.

CVE-2026-22246

CVE-2026-22246 is a medium-severity vulnerability in Joinmastodon Mastodon with a CVSS 3.x base score of 6.5. It is not currently listed as actively exploited by CISA, and its EPSS exploit-prediction score is low. The underlying weakness is classified as CWE-201.

Key facts

Severity: Medium (CVSS 3.x base score 6.5)
EPSS exploit prediction: 0% (14th percentile)
Actively exploited: Not listed in CISA KEV
EU (EUVD) id: EUVD-2026-1675
Weakness: CWE-201
Affected product: Joinmastodon Mastodon
Published: 2026-01-08
Last modified: 2026-06-17

Description

Mastodon is a free, open-source social network server based on ActivityPub. Mastodon 4.3 added notifications of severed relationships, allowing end-users to inspect the relationships they lost as the result of a moderation action. The code allowing users to download lists of severed relationships for a particular event fails to check the owner of the list before returning the lost relationships. Any registered local user can access the list of lost followers and followed users caused by any severance event, and go through all severance events this way. The leaked information does not include the name of the account which has lost follows and followers. This has been fixed in Mastodon v4.3.17, v4.4.11 and v4.5.4.

Frequently asked questions

What is CVE-2026-22246?: Mastodon is a free, open-source social network server based on ActivityPub. Mastodon 4.3 added notifications of severed relationships, allowing end-users to inspect the relationships they lost as the result of a moderation action. The code allowing users to download lists of severed relationships for a particular event fails to check the owner of the list before returning the lost relationships. Any registered local user can access the list of lost followers and followed users caused by any severance event, and go through all severance events this way. The leaked information does not include the name of the account which has lost follows and followers. This has been fixed in Mastodon v4.3.17, v4.4.11 and v4.5.4.
How severe is CVE-2026-22246?: CVE-2026-22246 has a CVSS 3.x base score of 6.5, rated medium severity. It is exploitable over network with low attack complexity, requires low privileges and no user interaction. Impact on confidentiality is high, integrity none, and availability none.
Is CVE-2026-22246 being actively exploited?: It is not currently listed in CISA's KEV catalog. Its EPSS exploit-prediction score is 0% (14th percentile), an estimate of the probability of exploitation in the next 30 days.
What products are affected by CVE-2026-22246?: CVE-2026-22246 affects Joinmastodon Mastodon. See the affected-products list for the exact vulnerable versions.
How do I fix CVE-2026-22246?: Review the linked vendor and NVD advisories for patched versions and mitigations, then upgrade or apply the recommended workaround.
Does CVE-2026-22246 have an EU (EUVD) identifier?: Yes. CVE-2026-22246 is tracked in the ENISA EU Vulnerability Database (EUVD) as EUVD-2026-1675.
When was CVE-2026-22246 published?: CVE-2026-22246 was published on 2026-01-08 and last updated on 2026-06-17.

References

Affected products (1)

cpe:2.3:a:joinmastodon:mastodon:*:*:*:*:*:*:*:*

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