Medium
Security advisory
An issue was discovered in Cyrus IMAP before 3.12.4. There is a Sieve mailbox existence oracle. An authenticated user could install a Sieve script that probed whether another user's private mailbox existed, or read the value of shared mailbox annotations, by observing which fileinto branch fired during LMTP delivery.
- Products
- Not specified
- Affected versions
- Not specified
- Fixed versions
- Not specified
- CVEs
- CVE-2026-61911
- Confirmed fixed CVEs
- Not specified
- Updated in this feed
- 4 Nov 2026, 08:27 UTC · Revision 1
Source evidence
An issue was discovered in Cyrus IMAP before 3.12.4. There is a Sieve mailbox existence oracle. An authenticated user could install a Sieve script that probed whether another user's private mailbox existed, or read the value of shared mailbox annotations, by observing which fileinto branch fired during LMTP delivery.
osv:CVE-2026-61911
Complete source record
{
"id": "f07517a892dd1a9cd47213585b38f8797af925e63e38b59cb3ecc64574b1d723",
"url": "https://osv.dev/vulnerability/CVE-2026-61911",
"method": "structured",
"payload": {
"kind": "advisory",
"title": "CVE-2026-61911",
"summary": "An issue was discovered in Cyrus IMAP before 3.12.4. There is a Sieve mailbox existence oracle. An authenticated user could install a Sieve script that probed whether another user's private mailbox existed, or read the value of shared mailbox annotations, by observing which fileinto branch fired during LMTP delivery.",
"evidence": "osv:CVE-2026-61911",
"products": [],
"severity": "medium",
"structured": {
"id": "CVE-2026-61911",
"aliases": [
"CVE-2026-61911"
],
"metrics": [
{
"type": "CVSS_V3",
"score": "CVSS:3.1/AV:N/AC:L/PR:L/UI:N/S:U/C:L/I:N/A:N"
}
],
"affected": [
{
"ranges": [
{
"repo": "https://github.com/cyrusimap/cyrus-imapd",
"type": "GIT",
"events": [
{
"introduced": "0"
},
{
"fixed": "08031fd42e027bdb5bc286e428a03e1c53c2e105"
},
{
"fixed": "ad6d4e67d0edbdf99e7ce31658c67640f30479c4"
},
{
"fixed": "f8ffbe4a87455c591fe355b03a2713a50f8441ab"
}
],
"database_specific": {
"extracted_events": [
{
"cpe": "cpe:2.3:a:cyrus:imap:*:*:*:*:*:*:*:*",
"range": [
{
"introduced": "0"
},
{
"fixed": "3.8.8"
}
],
"source": "CPE_RANGE"
},
{
"cpe": "cpe:2.3:a:cyrus:imap:*:*:*:*:*:*:*:*",
"range": [
{
"introduced": "3.9.0"
},
{
"fixed": "3.10.4"
}
],
"source": "CPE_RANGE"
},
{
"cpe": "cpe:2.3:a:cyrus:imap:*:*:*:*:*:*:*:*",
"range": [
{
"introduced": "3.11.0"
},
{
"fixed": "3.12.4"
}
],
"source": "CPE_RANGE"
}
]
}
}
],
"versions": [
"cyrus-imapd-3.8.7",
"cyrus-imapd-3.10.3",
"cyrus-imapd-3.12.3",
"cyrus-imapd-3.12.2",
"cyrus-imapd-3.8.6",
"cyrus-imapd-3.10.2",
"cyrus-imapd-3.12.1",
"cyrus-imapd-3.12.0",
"cyrus-imapd-3.12.0-rc1",
"cyrus-imapd-3.12.0-beta2",
"cyrus-imapd-3.8.5",
"cyrus-imapd-3.12.0-beta1",
"cyrus-imapd-3.10.1",
"cyrus-imapd-3.12.0-alpha0",
"cyrus-imapd-3.10.0",
"cyrus-imapd-3.8.4",
"cyrus-imapd-3.10.0-rc2",
"cyrus-imapd-3.8.3",
"cyrus-imapd-3.10.0-rc1",
"cyrus-imapd-3.8.2",
"cyrus-imapd-3.10.0-beta2",
"cyrus-imapd-3.10.0-beta1",
"cyrus-imapd-3.11.0-alpha0",
"cyrus-imapd-3.10.0-alpha0",
"cyrus-imapd-3.8.1",
"cyrus-imapd-3.8.0",
"cyrus-imapd-3.8.0-rc1",
"cyrus-imapd-3.8.0-beta2",
"cyrus-imapd-3.8.0-beta1",
"cyrus-imapd-3.9.0-alpha0",
"cyrus-imapd-3.8.0-alpha0",
"cyrus-imapd-3.7.0-alpha0",
"cyrus-imapd-3.5.0-alpha0",
"cyrus-imapd-3.3.1",
"cyrus-imapd-3.3.0",
"cyrus-imapd-3.3.0-dev0",
"cyrus-imapd-3.1.9",
"cyrus-imapd-3.1.8",
"cyrus-imapd-3.1.7",
"cyrus-imapd-3.1.6",
"cyrus-imapd-3.1.5",
"cyrus-imapd-3.1.4",
"cyrus-imapd-3.1.3",
"cyrus-imapd-3.1.2",
"cyrus-imapd-3.1.1",
"cyrus-imapd-3.0.0-rc4",
"cyrus-imapd-3.1.0-dev",
"cyrus-imapd-3.0.0-rc3",
"cyrus-imapd-3.0.0-rc2",
"cyrus-imapd-3.0.0-rc1",
"cyrus-imapd-3.0.0-beta6",
"cyrus-imapd-3.0.0-beta5",
"cyrus-imapd-3.0.0-beta4",
"cyrus-imapd-3.0.0-beta3",
"cyrus-imapd-3.0.0-beta2",
"cyrus-imapd-3.0.0-beta1",
"posttab",
"pretab",
"cyrus-imapd-2.5-snapshot-autoconf-and-automake",
"cyrus-imapd-2.4.2",
"cyrus-imapd-2.4.1",
"cyrus-imapd-2.4.0"
],
"database_specific": {
"source": "https://storage.googleapis.com/cve-osv-conversion/osv-output/CVE-2026-61911.json"
}
}
],
"modified": "2026-10-28T02:30:33.802047027Z",
"provider": "osv",
"references": [
"https://cyrusimap.org",
"https://www.cyrusimap.org/3.12/imap/download/release-notes/3.10/x/3.10.4.html",
"https://www.cyrusimap.org/3.12/imap/download/release-notes/3.12/x/3.12.4.html",
"https://www.cyrusimap.org/3.12/imap/download/release-notes/3.8/x/3.8.8.html",
"https://github.com/CVEProject/cvelistV5/tree/main/cves/2026/61xxx/CVE-2026-61911.json",
"https://nvd.nist.gov/vuln/detail/CVE-2026-61911"
],
"provider_metadata": {
"cwe_ids": [
"CWE-497"
],
"cna_assigner": "mitre",
"unresolved_ranges": [
{
"extracted_events": [
{
"range": [
{
"fixed": "3.8.8"
},
{
"introduced": "3.9.0"
},
{
"fixed": "3.10.4"
},
{
"introduced": "3.11.0"
},
{
"fixed": "3.12.4"
}
],
"source": "AFFECTED_FIELD",
"strategy": "StandardRange"
}
]
}
],
"osv_generated_from": "https://github.com/CVEProject/cvelistV5/tree/main/cves/2026/61xxx/CVE-2026-61911.json"
}
},
"related_cves": [
{
"value": "CVE-2026-61911",
"evidence": "/id"
}
],
"security_relevant": true,
"severity_evidence": "/severity/0/score"
},
"source_id": "core-osv",
"document_id": 501119,
"published_at": "2026-09-09T00:00:00+00:00"
}