High
Mastodon: Insufficient verification of email addresses
Type: advisorySources: OSV
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.
- Products
- Not specified
- Affected versions
- Not specified
- Fixed versions
- Not specified
- CVEs
- CVE-2026-41259
- Confirmed fixed CVEs
- Not specified
- Updated in this feed
- 3 Nov 2026, 10:52 UTC · Revision 1
Source evidence
Mastodon: Insufficient verification of email addresses
core-osv · Original sourcePublished 23 Apr 2026, 18:55 UTC
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.
osv:CVE-2026-41259
Complete source record
{
"id": "92ad8fd70e03488b39eda3cc41f20b865f5fe350d4361c7a791395aed23b29a0",
"url": "https://osv.dev/vulnerability/CVE-2026-41259",
"method": "structured",
"payload": {
"kind": "advisory",
"title": "Mastodon: Insufficient verification of email addresses",
"summary": "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.",
"evidence": "osv:CVE-2026-41259",
"products": [],
"severity": "high",
"structured": {
"id": "CVE-2026-41259",
"aliases": [
"BIT-mastodon-2026-41259",
"CVE-2026-41259",
"GHSA-5r37-qpwq-2jhh"
],
"metrics": [
{
"type": "CVSS_V4",
"score": "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"
}
],
"affected": [
{
"ranges": [
{
"repo": "https://github.com/mastodon/mastodon",
"type": "GIT",
"events": [
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},
{
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"database_specific": {
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"range": [
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{
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"source": "CPE_RANGE"
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"database_specific": {
"source": "https://storage.googleapis.com/cve-osv-conversion/osv-output/CVE-2026-41259.json"
}
}
],
"modified": "2026-10-28T02:30:28.112971234Z",
"provider": "osv",
"references": [
"https://github.com/CVEProject/cvelistV5/tree/main/cves/2026/41xxx/CVE-2026-41259.json",
"https://github.com/mastodon/mastodon/security/advisories/GHSA-5r37-qpwq-2jhh",
"https://nvd.nist.gov/vuln/detail/CVE-2026-41259"
],
"provider_metadata": {
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],
"cna_assigner": "GitHub_M",
"osv_generated_from": "https://github.com/CVEProject/cvelistV5/tree/main/cves/2026/41xxx/CVE-2026-41259.json"
}
},
"related_cves": [
{
"value": "CVE-2026-41259",
"evidence": "/id"
}
],
"security_relevant": true,
"severity_evidence": "/severity/0/score"
},
"source_id": "core-osv",
"document_id": 494671,
"published_at": "2026-04-23T18:55:20.854+00:00"
}