How severe is CVE-2026-23962?

CVE-2026-23962 has a CVSS 3.x base score of 7.5, rated high severity. It is exploitable over network with low attack complexity, requires no privileges and no user interaction. Impact on confidentiality is none, integrity none, and availability high.

Is CVE-2026-23962 being actively exploited?

It is not currently listed in CISA's KEV catalog. Its EPSS exploit-prediction score is 0% (38th percentile), an estimate of the probability of exploitation in the next 30 days.

What products are affected by CVE-2026-23962?

CVE-2026-23962 affects Joinmastodon Mastodon. See the affected-products list for the exact vulnerable versions.

How do I fix CVE-2026-23962?

Review the linked vendor and NVD advisories for patched versions and mitigations, then upgrade or apply the recommended workaround. Given its high severity, prioritise patching exposed systems.

Does CVE-2026-23962 have an EU (EUVD) identifier?

Yes. CVE-2026-23962 is tracked in the ENISA EU Vulnerability Database (EUVD) as EUVD-2026-4208.

When was CVE-2026-23962 published?

CVE-2026-23962 was published on 2026-01-22 and last updated on 2026-06-17.

CVE-2026-23962

CVE-2026-23962 is a high-severity vulnerability in Joinmastodon Mastodon with a CVSS 3.x base score of 7.5. 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-770.

Key facts

Severity: High (CVSS 3.x base score 7.5)
EPSS exploit prediction: 0% (38th percentile)
Actively exploited: Not listed in CISA KEV
EU (EUVD) id: EUVD-2026-4208
Weakness: CWE-770
Affected product: Joinmastodon Mastodon
Published: 2026-01-22
Last modified: 2026-06-17

Description

Mastodon is a free, open-source social network server based on ActivityPub. Mastodon versions before v4.3.18, v4.4.12, and v4.5.5 do not have a limit on the maximum number of poll options for remote posts, allowing attackers to create polls with a very large amount of options, greatly increasing resource consumption. Depending on the number of poll options, an attacker can cause disproportionate resource usage in both Mastodon servers and clients, potentially causing Denial of Service either server-side or client-side. Mastodon versions v4.5.5, v4.4.12, v4.3.18 are patched.

Frequently asked questions

What is CVE-2026-23962?: Mastodon is a free, open-source social network server based on ActivityPub. Mastodon versions before v4.3.18, v4.4.12, and v4.5.5 do not have a limit on the maximum number of poll options for remote posts, allowing attackers to create polls with a very large amount of options, greatly increasing resource consumption. Depending on the number of poll options, an attacker can cause disproportionate resource usage in both Mastodon servers and clients, potentially causing Denial of Service either server-side or client-side. Mastodon versions v4.5.5, v4.4.12, v4.3.18 are patched.
How severe is CVE-2026-23962?: CVE-2026-23962 has a CVSS 3.x base score of 7.5, rated high severity. It is exploitable over network with low attack complexity, requires no privileges and no user interaction. Impact on confidentiality is none, integrity none, and availability high.
Is CVE-2026-23962 being actively exploited?: It is not currently listed in CISA's KEV catalog. Its EPSS exploit-prediction score is 0% (38th percentile), an estimate of the probability of exploitation in the next 30 days.
What products are affected by CVE-2026-23962?: CVE-2026-23962 affects Joinmastodon Mastodon. See the affected-products list for the exact vulnerable versions.
How do I fix CVE-2026-23962?: Review the linked vendor and NVD advisories for patched versions and mitigations, then upgrade or apply the recommended workaround. Given its high severity, prioritise patching exposed systems.
Does CVE-2026-23962 have an EU (EUVD) identifier?: Yes. CVE-2026-23962 is tracked in the ENISA EU Vulnerability Database (EUVD) as EUVD-2026-4208.
When was CVE-2026-23962 published?: CVE-2026-23962 was published on 2026-01-22 and last updated on 2026-06-17.

References

Affected products (1)

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

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