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CVE-2026-33604· NVD / CVE Program· CNA OX

An attacker that can get Dovecot to relay a message, for example through Sieve redirect or submission relay, can use a crafted line ending i

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: Open-Xchange GmbH OX Dovecot CE 2.4.5; Open-Xchange GmbH OX Dovecot Pro 2.3.22.2, 3.0.7, 3.1.6.

Low priority for now. Upgrade to Open-Xchange GmbH OX Dovecot CE 2.4.5; Open-Xchange GmbH OX Dovecot Pro 2.3.22.2, 3.0.7, 3.1.6 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

An attacker that can get Dovecot to relay a message, for example through Sieve redirect or submission relay, can use a crafted line ending in the message body to bypass the outbound protection that prevents message content from being interpreted as SMTP commands. A downstream mail server that hasn't yet fixed the SMTP smuggling vulnerability can be tricked into treating part of the message body as new SMTP commands, allowing injection of spoofed email. This is the same vulnerability class as CVE-2023-51764 and CVE-2023-51766. Where you control the receiving mail servers, ensure they reject bare carriage returns in message data. Update to non-vulnerable version. No publicly available exploits are known.

MediumCVSS 5.9 · v3.1—No exploit Fix available
Published
Aug 28, 2026
Updated
Sep 3, 2026
EPSS
0.3% · 22th 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
partial

Vulnrichment: CISA's decision-tree inputs.

CNA vs NVD score

NVD
—
CNA · OX
5.9
NVD has not scored this yet; the score shown is the CNA’s.

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-2026-33604

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.

—

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 CE

    • 2.3.0 and later · before 2.4.5affected · semver

  • Open-Xchange GmbH OX Dovecot Pro

    • 2.3.0 and later · before 2.3.22.2affected · semver
    • 3.0.0 and later · before 3.0.7affected · semver
    • 3.1.0 and later · before 3.1.6affected · semver

Package-level exposure

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

EcosystemPackageAffected rangeFix
Alpine:v3.23dovecotbefore 2.4.5-r02.4.5-r0
Debian:12dovecotfrom 0—
Debian:13dovecotbefore 1:2.4.1+dfsg1-6+deb13u71:2.4.1+dfsg1-6+deb13u7
Debian:14dovecotbefore 1:2.4.5+dfsg1-11:2.4.5+dfsg1-1
openSUSE:Leap 16.0dovecot24before 2.4.4-160000.2.12.4.4-160000.2.1
openSUSE:Tumbleweeddovecot24before 2.4.5-1.12.4.5-1.1
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 12 SP5-LTSSdovecot22before 2.2.31-19.40.12.2.31-19.40.1
SUSE:Linux Enterprise Server 16.0dovecot24before 2.4.4-160000.2.12.4.4-160000.2.1

Same product

open-xchange gmbh: all records

Other highest-scoring records for the same primary product.

  • CVE-2026-42007An attacker that has valid credentials can use a Sieve script with the editheader extension to trigger a use-after-free in the mail editing
    36Monitor
  • CVE-2026-42391An unauthenticated attacker can send an IMAP ID command with a very large number of parameters before logging in, which causes memory and CP
    30Monitor
  • CVE-2026-33605An unauthenticated attacker can crash the ManageSieve login process by sending a small malformed command before authenticating.
    30Monitor

Published before and after this one in the same product

  • ← EarlierCVE-2026-27852Aug 28, 2026 · An attacker that can send mail to a user can craft a message whose headers contain a very large number of email addresses or MIME parameters
    30Monitor
  • ← EarlierCVE-2026-33263Aug 28, 2026 · When mail_max_userip_connections is set (default 10) and reached, submission-login can crash with epoll() panic caused by file descriptor ha
    17Monitor
  • Later →CVE-2026-33606Aug 28, 2026 · Mail content stored by a user can be crafted so that it is interpreted as dsync protocol commands when an administrator later runs dsync wit
    19Monitor

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
Open-Xchange GmbH OX Dovecot CE2.4.5Vendor (CNA)
Open-Xchange GmbH OX Dovecot Pro2.3.22.2Vendor (CNA)
Open-Xchange GmbH OX Dovecot Pro3.0.7Vendor (CNA)
Open-Xchange GmbH OX Dovecot Pro3.1.6Vendor (CNA)
alpine:dovecot2.4.5-r0 · Alpine:v3.23Package registry (OSV)
debian:dovecot1:2.4.1+dfsg1-6+deb13u7 · Debian:13Package registry (OSV)
opensuse:dovecot242.4.5-1.1 · openSUSE:TumbleweedPackage registry (OSV)
suse:dovecot222.2.31-19.40.1 · SUSE:Linux Enterprise Server 12 SP5-LTSSPackage registry (OSV)
suse:dovecot232.3.21.1-150200.76.1 · SUSE:Linux Enterprise Module for Server Applications 15 SP7Package registry (OSV)
suse:dovecot242.4.4-160000.2.1 · 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.

EPSS, last 120 days

FIRST EPSS daily score; only changes of 0.01 or more are recorded (step chart).

Patch and commit links

Commit, PR and diff links among the references. A starting point for patch-diffing and variant hunting; fixes, not exploits.

No commit or PR link among the references.

Credits

All researchers

Finders, reporters and analysts named in the CNA record. Click a name for that researcher’s other records.

No credits in the CNA record.

Variant candidates

Same product, same weakness class, within 18 months. If the patch missed the root cause, the sibling bug is here.

No nightly-computed relations.

Chain candidates

An authentication bypass and a privilege-requiring bug in the same product, published close together: combined they may become an unauthenticated path.

—

Bug bounty scope

No known public program.

Source: bounty-targets-data (public HackerOne, Bugcrowd, Intigriti, YesWeHack listings).

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

Weakness class (CWE)

CWE-655 · Insufficient Psychological Acceptability

CVSS vector

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

nvd-secondary

Attack context

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

MITRE has no CAPEC/ATT&CK mapping for this CWE.

Change log

  1. Fix✗ → ✓

For records you follow, these changes also arrive as notifications. →

References

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

All records