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NVD / CVE Program· CNA OX

CVE-2026-27855: Dovecot OTP authentication is vulnerable to replay attack under specific conditions.

MediumCVSS 5.9 · v3.1—No exploit Fix available

Noroxi assessment

Priority: Monitor (action score 23/100)

  • The sources we track (CISA KEV, Exploit-DB, Metasploit, Nuclei, GitHub) show no public exploit code or exploitation in the wild.
  • Probability of exploitation in the next 30 days: 0.31% (FIRST EPSS).
  • Anyone who can reach it over the internet can trigger it. No account or password is required. No user action is required. Special conditions such as timing or configuration are required.
  • Fixed version: dovecot (Alpine:v3.23) 2.4.3-r0; dovecot (Debian:12) 1:2.3.19.1+dfsg1-2.1+deb12u2; dovecot (Debian:13) 1:2.4.1+dfsg1-6+deb13u4.

Low priority for now. Upgrade to dovecot (Alpine:v3.23) 2.4.3-r0; dovecot (Debian:12) 1:2.3.19.1+dfsg1-2.1+deb12u2; dovecot (Debian:13) 1:2.4.1+dfsg1-6+deb13u4 or later.

Generated automatically from the record's data: CVSS (NVD and CNA), CISA KEV and SSVC, FIRST EPSS, exploit sources, fixed versions. How we calculate it

Primary sources: NVD · CVE.org · FIRST EPSS

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
Mar 27, 2026
Updated
Oct 26, 2026
EPSS
0.3% · 24th percentile

Report tools

JSON

Action score

23

Monitor

Low priority for now.

CVSS
23 / 40 · 5.9 / 10
CISA KEV
0 / 30 · Not listed
EPSS
0 / 30 · 0.3%

CISA SSVC decision

Exploitation
none
Automatable
no
Technical impact
total

Vulnrichment: CISA's decision-tree inputs.

CNA vs NVD score

NVD
5.9
CNA · OX
6.8
0.9 point gap

CVSS:3.1/AV:N/AC:H/PR:N/UI:R/S:U/C:H/I:H/A:N

The score given by the assigning authority versus NVD’s independent score. A gap means the severity is contested.

Get told when this record changes

  • Not in KEV: no record of exploitation in the wild
  • No public exploit code on record
  • A fix has been released

If any of these changes, we'll tell you in the daily email digest.

Follow CVE-2026-27855

When you'll hear from us

  • when it enters CISA KEV
  • when exploit code appears or is weaponized
  • when the record is updated (including a fixed version)
  • when EPSS rises 20 points in a week

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Noroxi analysis

What does it mean in your environment?

The assessment above is generated automatically from the record's data; it doesn't know your environment. Our team verifies on your systems whether this vulnerability is actually exploitable and which mitigation is enough.

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Affected systems

Is your version affected?

Pick the product and type the version you run. It's compared with this record's version ranges in your browser; the version isn't sent anywhere.

VendorProduct
dovecotdovecot
open-xchangedovecot

Using dovecot? Add it to your stack and be the first to know about CVEs like this one. (Email server)

Watch new CVEs for dovecot

When you'll hear from us

  • when a new CVE affecting this product is published
  • when a record in your stack enters KEV or is weaponized

One daily email digest (06:00 UTC); connect a webhook for KEV listings and weaponized exploits every 10 minutes on paid plans, on the hour on the free plan.

Your free account also gets you

  • CVE alerts: add the products and versions you run, get the new CVEs that affect them
  • Uptime monitoring: 1 site, instant email when it goes down
  • Add your domain: subdomains and takeover risk scanned every week (1 domain)
  • 10 scans an hour on the security tools, at most 30 a day (3 a day without an account), an API key and MCP
  • All your scans in one panel: findings, what changed in the last scan, a report per domain or per client (PDF, share link)
All free tools

Sign up with email · Have an account? Sign in

Free account, no card. Unfollow any time.

Don't want an account? Get "Exploited this week" by email every Monday

Versions reported by the vendor

Affected version ranges reported by the assigning authority (OX). Independent of NVD's CPE analysis and usually ahead of it.

  • Open-Xchange GmbH OX Dovecot Pro

    • up to and including 2.3.0affected · semver

Affected versions

NVD version ranges (for catalog products). Add the product to your stack with a version and matching uses these.

  • dovecot dovecotbefore 2.4.3
  • open-xchange dovecotup to 2.3.0 inclusive

Package-level exposure

OSV and GitHub Advisory data: ecosystem, package and range. SBOM matching uses this table.

EcosystemPackageAffected rangeFix
Alpine:v3.23dovecotbefore 2.4.3-r02.4.3-r0
Debian:12dovecotbefore 1:2.3.19.1+dfsg1-2.1+deb12u21:2.3.19.1+dfsg1-2.1+deb12u2
Debian:13dovecotbefore 1:2.4.1+dfsg1-6+deb13u41:2.4.1+dfsg1-6+deb13u4
Debian:14dovecotbefore 1:2.4.3+dfsg1-11:2.4.3+dfsg1-1
openSUSE:Leap 16.0dovecot24before 2.4.3-160000.1.12.4.3-160000.1.1
openSUSE:Tumbleweeddovecot24before 2.4.3-1.12.4.3-1.1
SUSE:Linux Enterprise Module for Server Applications 15 SP7dovecot23before 2.3.21.1-150200.76.12.3.21.1-150200.76.1
SUSE:Linux Enterprise Server 16.0dovecot24before 2.4.3-160000.1.12.4.3-160000.1.1

Same product

dovecot: all records

Other highest-scoring records for the same primary product.

  • CVE-2019-11500In Dovecot before 2.2.36.4 and 2.3.x before 2.3.7.2 (and Pigeonhole before 0.5.7.2), protocol processing can fail for quoted strings.
    58Plan
  • CVE-2020-7046lib-smtp in submission-login and lmtp in Dovecot 2.3.9 before 2.3.9.3 mishandles truncated UTF-8 data in command parameters, as…
    45Plan
  • CVE-2016-8652The auth component in Dovecot before 2.2.27, when auth-policy is configured, allows a remote attackers to cause a denial of service (crash)…
    37Monitor

Published before and after this one in the same product

  • ← EarlierCVE-2026-0394Mar 27, 2026 · When dovecot has been configured to use per-domain passwd files, and they are placed one path component above /etc, or slash has been added…
    21Monitor
  • ← EarlierCVE-2026-24031Mar 27, 2026 · Dovecot SQL based authentication can be bypassed when auth_username_chars is cleared by admin.
    32Monitor
  • Later →CVE-2026-27856Mar 27, 2026 · Doveadm credentials are verified using direct comparison which is susceptible to timing oracle attack.
    23Monitor

Remediation

Which version to upgrade to

Fix versions compiled from the vendor, package registries and Microsoft. Verify the vendor's note before upgrading.

Product / packageFixed versionSource
alpine:dovecot2.4.3-r0 · Alpine:v3.23Package registry (OSV)
debian:dovecot1:2.3.19.1+dfsg1-2.1+deb12u2 · Debian:12Package registry (OSV)
opensuse:dovecot242.4.3-1.1 · openSUSE:TumbleweedPackage registry (OSV)
suse:dovecot232.3.21.1-150200.76.1 · SUSE:Linux Enterprise Module for Server Applications 15 SP7Package registry (OSV)
suse:dovecot242.4.3-160000.1.1 · SUSE:Linux Enterprise Server 16.0Package registry (OSV)

Exploit status

No known public exploit

No public exploit has been observed yet. That doesn't mean you're safe, only that the bar is a little higher.

Research context

For pentesters and researchers: attack profile, score disagreement, timeline, patch commits, credits, variant and chain candidates, bug bounty scope. All derived from existing data; no exploit code.

Timeline

From publication to today: proof of concept, Metasploit module, CISA KEV and fix record. Dates are as reported by the sources.

No dated events beyond publication.

Not on record for this CVE: EPSS history · patch commit or PR link · researcher credit · variant or chain candidate · public bounty program.

Technical details

Attack conditions

  • Anyone who can reach it over the internet can trigger it.
  • No account or password is required.
  • No user action is required.
  • Special conditions such as timing or configuration are required.

If successful

Confidentiality
high · data can be read
Integrity
none
Availability
none
Attack vector
Network
Attack complexity
High
Privileges required
None
User interaction
None
Scope
Unchanged
Confidentiality impact
High
Integrity impact
None
Availability impact
None

Weakness class (CWE)

CWE-294 · Authentication Bypass by Capture-replay

CVSS vector

CVSS:3.1/AV:N/AC:H/PR:N/UI:N/S:U/C:H/I:N/A:N

nvd-primary

Attack context

MITRE CAPEC attack patterns and ATT&CK techniques for this weakness class (CWE). A starting point for detection rules and threat hunting.

References

Vendor advisories and official records. Exploit/PoC links are deliberately left out.

All records