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VulnerabilityPublished

CVE-2026-41259: mastodon · Improper Enforcement of Behavioral Workflow

Affects mastodonSource GCVE Database

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Not known to be exploited · CVSS 8.2 High · fixed in 4.5.9 : patch mastodon soon.

Data as of 12 Nov 2026, 01:19 UTC

CVSS 4.0 base score
8.2High
How severe the flaw is on the 0–10 CVSS scale.

Thin evidence

One scorer or none
CVSS scores by source
CNA (GitHub_M)CVSS 4.08.2
Patch
Available – fixed in 4.5.9, 4.4.16, 4.3.22
CVSS:4.0/AV:N/AC:L/AT:P/PR:N/UI:N/VC:N/VI:H/VA:N/SC:N/SI:N/SA:N

Exploitation evidence

  1. Disclosed: evidence found.

    CVE published 23 Apr 2026

  2. Detectable: no evidence on record.

    No public nuclei template indexed

  3. Weaponized: no evidence on record.

    No public exploit code indexed in Metasploit or Exploit-DB

  4. Exploited in the wild: no evidence on record.

    Not in CISA KEV and no source reports exploitation

  5. Observed by OffSeq 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 11 Nov 2026.

What to do

Upgrade mastodon to 4.5.9, 4.4.16 or 4.3.22.

Affected software

ProductAffectedFixed in
mastodon mastodonAffected
  • <4.3.22
  • >=4.4.0-beta.1 <4.4.16
  • >=4.5.0-beta.1 <4.5.9
Fixed in
  • 4.3.22
  • 4.4.16
  • 4.5.9

AI-suggested

This vulnerability is fixed in Mastodon versions 4.3.22, 4.4.16, and 4.5.9. Users and administrators should upgrade to at least these versions to remediate the issue. No additional mitigation steps are indicated by the vendor advisory.

Description

Mastodon versions prior to 4.3.22, 4.4.16, and 4.5.9 contain a vulnerability where the platform's restriction on new user sign-ups by e-mail domain names fails to properly restrict certain characters. These characters can be interpreted differently by some mail servers, leading to improper enforcement of behavioral workflow. This issue is addressed in versions 4.3.22, 4.4.16, and 4.5.9.

References

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