| Name | CVE-2026-27856 |
| Description | Doveadm credentials are verified using direct comparison which is susceptible to timing oracle attack. An attacker can use this to determine the configured credentials. Figuring out the credential will lead into full access to the affected component. Limit access to the doveadm http service port, install fixed version. No publicly available exploits are known. |
| Source | CVE (at NVD; CERT, ENISA, LWN, oss-sec, fulldisc, Debian ELTS, Red Hat, Ubuntu, Gentoo, SUSE bugzilla/CVE, GitHub advisories/code/issues, web search, more) |
| References | DSA-6197-1 |
The table below lists information on source packages.
| Source Package | Release | Version | Status |
|---|---|---|---|
| dovecot (PTS) | bullseye | 1:2.3.13+dfsg1-2+deb11u1 | vulnerable |
| bullseye (security) | 1:2.3.13+dfsg1-2+deb11u2 | vulnerable | |
| bookworm | 1:2.3.19.1+dfsg1-2.1+deb12u1 | vulnerable | |
| bookworm (security) | 1:2.3.19.1+dfsg1-2.1+deb12u3 | fixed | |
| trixie | 1:2.4.1+dfsg1-6+deb13u3 | vulnerable | |
| trixie (security) | 1:2.4.1+dfsg1-6+deb13u4 | fixed | |
| forky | 1:2.4.2+dfsg1-4 | vulnerable | |
| sid | 1:2.4.3+dfsg1-1 | fixed |
The information below is based on the following data on fixed versions.
| Package | Type | Release | Fixed Version | Urgency | Origin | Debian Bugs |
|---|---|---|---|---|---|---|
| dovecot | source | bookworm | 1:2.3.19.1+dfsg1-2.1+deb12u2 | DSA-6197-1 | ||
| dovecot | source | trixie | 1:2.4.1+dfsg1-6+deb13u4 | DSA-6197-1 | ||
| dovecot | source | (unstable) | 1:2.4.3+dfsg1-1 |
https://dovecot.org/mailman3/archives/list/dovecot-news@dovecot.org/thread/IKIHZX77IPTGSP5WBIPJUOFBUQFKVPE7/
https://documentation.open-xchange.com/dovecot/security/advisories/html/2026/oxdc-adv-2026-0001.html#cve-2026-27856-doveadm-credentials-verified-without-timing-safety
Fixed by: https://github.com/dovecot/core/commit/1864d4890499bc2b29fa1b62fe04073dd2bf0c57 (2.4.3)
Fixed by: https://github.com/dovecot/core/commit/b3fb5b342ad04dba1239a043206beda2bf14be9d (2.4.3)
Fixed by: https://github.com/dovecot/core/commit/8a0cde2a22d872853166f2d383b350aa4ca4974a (2.4.3)