CVE-2026-41259

Mastodon: Insufficient verification of email addresses

HIGH

7.5

CVSS Score

Published: April 23, 2026 at 06:55 PM UTC

Updated: June 17, 2026 at 10:46 AM UTC

2 products affected across 2 vendorsMastodonMastodon

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Severity

HIGH7.5

Exploit prediction

EPSS 0.2%

SSVC

No known exploit

Description

Mastodon is a free, open-source social network server based on ActivityPub. Prior to v4.5.9, v4.4.16, and v4.3.22, Mastodon allows restricting new user sign-up based on e-mail domain names, and performs basic validation on e-mail addresses, but fails to restrict characters that are interpreted differently by some mailing servers. This vulnerability is fixed in v4.5.9, v4.4.16, and v4.3.22.

Affected

Our own answer: ranges merged, affected separated from platform-only, with confidence and review flags.

Mastodon · Joinmastodon

95%

v < 4.3.224.4.0 ≤ v < 4.4.164.5.0 ≤ v < 4.5.9

Mastodon · Mastodon

60%

v < 4.3.22v < 4.4.16v < 4.5.9

Affected range stops below 4.3.22, so it looks safe — our inference, not a vendor statement

Affected range stops below 4.4.16, so it looks safe — our inference, not a vendor statement

Affected range stops below 4.5.9, so it looks safe — our inference, not a vendor statement

Remediation

No guide yet

No remediation guidance has been written for this CVE yet. What the record does show:

Patch and advisory references

https://github.com/mastodon/mastodon/security/advisories/GHSA-5r37-qpwq-2jhh

References (1)

x_refsource_CONFIRMVendor Advisory

Source: cverecord

https://github.com/mastodon/mastodon/security/advisories/GHSA-5r37-qpwq-2jhh

SSVC — Action Prioritization

SSVCNo known exploitAutomatablePartial impact

SSVC signals action urgency (what to patch first), separate from CVSS which measures severity.

CVSS

7.5HIGH[email protected]

Attack Vector: NETWORK
Complexity: LOW
Privileges: NONE
User Interaction: NONE
Scope: UNCHANGED
Confidentiality: NONE
Integrity: HIGH
Availability: NONE

Vector?

Quick Info

StatusANALYZED

CWE

CWE-841

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