CVE-2026-27855

Dovecot OTP authentication is vulnerable to replay attack under specific conditions. If auth cache is enabled, and username is altered in passdb, then OTP credentials can be cached so that same OTP reply is valid. An attacker able to observe an OTP exchange is able to log in as the user. If authentication happens over unsecure connection, switch to SCRAM protocol. Alternatively ensure the communcations are secured, and if possible switch to OAUTH2 or SCRAM. No publicly available exploits are known.

Published: 2026-03-27 Last update: 2026-04-29 Assigner: [email protected] Source: [email protected]
NVD Status：Analyzed，CVE State: published
View at NVD, CVE.org, EUVD

CVE-2026-27855 is rated Low Risk (36.4/100): CVSS Medium severity, with low exploitation likelihood (EPSS 0.34%). Monitor for updates and reassess as exploit intelligence or EPSS changes.

Risk is dynamic; we continuously reassess and refresh what is shown on this page as upstream context changes.

Exploit prediction scoring system (EPSS) score for CVE-2026-27855

EPSS lead: Daily EPSS estimates relative likelihood of exploitation; percentile ranks this CVE among scored vulnerabilities (higher = more severe relative rank).

# Date Old EPSS score New EPSS score Delta (New - Old)
1 2026-06-15 0.04% 0.34% +0.30%
2 2026-03-27 — 0.04% —

Full EPSS history (2 records total)

Common vulnerability scoring system (CVSS) metrics for CVE-2026-27855

CVSS metrics for this CVE.

Base score Version Severity Vector Exploitability Impact Score source
6.8 3.1 MEDIUM
CVSS:3.1/AV:N/AC:H/PR:N/UI:R/S:U/C:H/I:H/A:N Click to expand
Attack vector (AV:N)
Could be attacked over the internet or any normal routed network—not just someone sitting at the machine.
Attack complexity (AC:H)
Even with access, the exploit needs extra luck, timing, or a fussy environment to actually work.
Privileges required (PR:N)
No account or special rights needed—anonymous or random user is enough.
User interaction (UI:R)
A real person has to do something—click, install, enable—otherwise it doesn’t land.
Scope (S:U)
Damage stays in the same “trust bubble” as the broken component—no big spill into unrelated systems.
Confidentiality (C:H)
Serious risk that confidential data gets exposed in a big way.
Integrity (I:H)
They could widely tamper with or forge data—trust in the data is badly hurt.
Availability (A:N)
Service keeps running; no real outage angle.
 1.6 5.2 [email protected]
5.9 3.1 MEDIUM
CVSS:3.1/AV:N/AC:H/PR:N/UI:N/S:U/C:H/I:N/A:N Click to expand
Attack vector (AV:N)
Could be attacked over the internet or any normal routed network—not just someone sitting at the machine.
Attack complexity (AC:H)
Even with access, the exploit needs extra luck, timing, or a fussy environment to actually work.
Privileges required (PR:N)
No account or special rights needed—anonymous or random user is enough.
User interaction (UI:N)
Nobody has to click “OK” or open a trap file; it can work without a victim helping.
Scope (S:U)
Damage stays in the same “trust bubble” as the broken component—no big spill into unrelated systems.
Confidentiality (C:H)
Serious risk that confidential data gets exposed in a big way.
Integrity (I:N)
Data isn’t meaningfully altered or forged.
Availability (A:N)
Service keeps running; no real outage angle.
 2.2 3.6 [email protected]

Weakness enumeration for CVE-2026-27855

OS Trackers for CVE-2026-27855

vendor priority summary link
alpine — CVE-2026-27855: 1 source package rows (dovecot); 2 state rows across 2 repos (3.23-main, edge-main); fixed 2, open 0. https://security.alpinelinux.org/vuln/CVE-2026-27855
debian not yet assigned CVE-2026-27855 not yet assigned priority: Debian including 1 source packages (dovecot), 5 status rows across 5 suites (bookworm, bullseye, forky, sid, trixie): resolved 5. https://security-tracker.debian.org/tracker/CVE-2026-27855
redhat medium — https://access.redhat.com/security/cve/CVE-2026-27855
suse medium CVE-2026-27855 severity moderate: SUSE including 8 source package names (dovecot24-2.4.3-1.1, dovecot24-backend-mysql-2.4.3-1.1, …), 8 product×package rows across 1 product lines (openSUSE Tumbleweed): Fixed 8. https://www.suse.com/security/cve/CVE-2026-27855/
ubuntu medium CVE-2026-27855 medium priority: Ubuntu including 1 source packages (dovecot), 8 status rows across 8 suites (bionic, focal, jammy, noble, questing, trusty, upstream, xenial): needed 4, released 4. https://ubuntu.com/security/CVE-2026-27855

Affected software / configurations for CVE-2026-27855

Vendor Product Version Raw CPE
dovecot dovecot < 2.4.3 cpe:2.3:a:dovecot:dovecot:*:*:*:*:*:*:*:*
open-xchange dovecot <= 2.3.0 cpe:2.3:a:open-xchange:dovecot:*:*:*:*:pro:*:*:*

References for CVE-2026-27855

cvelogic Threat Intelligence