What is CVE-2026-50129?

Mastodon is a free, open-source social network server based on ActivityPub. Prior to 4.5.11, 4.4.18, and 4.3.24, a DoS can be triggered by (Uncaught Exception vulerability), due to missing exception handling in the math sanitizer. Malformed nodes can result in a DoS of a whole server or targeted users services, depending on the type of action that includes the malformed nodes and the services interacting with it. This vulnerability is fixed in 4.5.11, 4.4.18, and 4.3.24.

How severe is CVE-2026-50129?

CVE-2026-50129 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-2026-50129 being actively exploited?

It is not currently listed in CISA's KEV catalog. Its EPSS exploit-prediction score is 0% (18th percentile), an estimate of the probability of exploitation in the next 30 days.

How do I fix CVE-2026-50129?

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-2026-50129 have an EU (EUVD) identifier?

Yes. CVE-2026-50129 is tracked in the ENISA EU Vulnerability Database (EUVD) as EUVD-2026-39060.

When was CVE-2026-50129 published?

CVE-2026-50129 was published on 2026-06-24 and last updated on 2026-06-25.

CVE-2026-50129

CVE-2026-50129 is a high-severity vulnerability 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-248.

Key facts

Severity: High (CVSS 3.x base score 7.5)
EPSS exploit prediction: 0% (18th percentile)
Actively exploited: Not listed in CISA KEV
EU (EUVD) id: EUVD-2026-39060
Weakness: CWE-248
Published: 2026-06-24
Last modified: 2026-06-25

Description

Mastodon is a free, open-source social network server based on ActivityPub. Prior to 4.5.11, 4.4.18, and 4.3.24, a DoS can be triggered by (Uncaught Exception vulerability), due to missing exception handling in the math sanitizer. Malformed <math> nodes can result in a DoS of a whole server or targeted users services, depending on the type of action that includes the malformed nodes and the services interacting with it. This vulnerability is fixed in 4.5.11, 4.4.18, and 4.3.24.

Frequently asked questions

What is CVE-2026-50129?: Mastodon is a free, open-source social network server based on ActivityPub. Prior to 4.5.11, 4.4.18, and 4.3.24, a DoS can be triggered by (Uncaught Exception vulerability), due to missing exception handling in the math sanitizer. Malformed <math> nodes can result in a DoS of a whole server or targeted users services, depending on the type of action that includes the malformed nodes and the services interacting with it. This vulnerability is fixed in 4.5.11, 4.4.18, and 4.3.24.
How severe is CVE-2026-50129?: CVE-2026-50129 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-2026-50129 being actively exploited?: It is not currently listed in CISA's KEV catalog. Its EPSS exploit-prediction score is 0% (18th percentile), an estimate of the probability of exploitation in the next 30 days.
How do I fix CVE-2026-50129?: 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-2026-50129 have an EU (EUVD) identifier?: Yes. CVE-2026-50129 is tracked in the ENISA EU Vulnerability Database (EUVD) as EUVD-2026-39060.
When was CVE-2026-50129 published?: CVE-2026-50129 was published on 2026-06-24 and last updated on 2026-06-25.

References

https://github.com/mastodon/mastodon/security/advisories/GHSA-qrgq-9fx2-vf2r

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