Description
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.
Affected products
| Vendor | Product | Affected | Fixed |
|---|---|---|---|
| cyrusimap | Cyrus IMAP | < 3.8.8, 3.9.0 – < 3.10.4, 3.11.0 – < 3.12.4 | 3.8.8 |
Fixed in Linux distributions
Distributions backport fixes, so the version that fixes this vulnerability differs per release — upgrade to at least the version shown. From the distributions' security trackers and advisories.
Debian
Security tracker ↗| Release | Package | Fixed in | Advisory |
|---|---|---|---|
| Debian 14 | cyrus-imapd | 3.12.4-1 | — |
| Debian 13 | cyrus-imapd | No fix yet | — |
| Debian 12 | cyrus-imapd | No fix yet | — |
Ubuntu
Security tracker ↗| Release | Package | Fixed in | Advisory |
|---|---|---|---|
| Ubuntu 26.10 | cyrus-imapd | No fix yet | — |
| Ubuntu 26.04 LTS | cyrus-imapd | No fix yet | — |
Show 4 more (older releases, extended support, other products)Fewer releases
| Release | Package | Fixed in | Advisory |
|---|---|---|---|
| Ubuntu Pro 24.04 LTS | cyrus-imapd | No fix yet | — |
| Ubuntu Pro 22.04 LTS | cyrus-imapd | No fix yet | — |
| Ubuntu Pro 20.04 LTS | cyrus-imapd | No fix yet | — |
| Ubuntu Pro 18.04 LTS | cyrus-imapd | No fix yet | — |
openSUSE
Security tracker ↗| Release | Package | Fixed in | Advisory |
|---|---|---|---|
| openSUSE Leap 16.0 | cyrus-imapd | 3.8.8-bp160.1.1 | openSUSE-SU-2026:21929-1 |
Advisories 2
- openSUSE-SU-2026:21929-1 Security update for cyrus-imapd SUSE / openSUSE Security Updates · Sep 25, 2026
- WID-SEC-2026-3301 cyrus imap: Mehrere Schwachstellen BSI CERT-Bund (WID) · Sep 24, 2026