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NVD / CVE Program· CNA OX

CVE-2026-33603: Attacker can use a specially crafted base64 exchange between Dovecot and Client to fake SCRAM TLS channel binding.

MediumCVSS 5.3 · v3.1—No exploit Fix available

Noroxi assessment

Priority: Monitor (action score 21/100)

  • 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: 0.21% (FIRST EPSS).
  • Someone on the same network segment 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) 2.4.4-r0; dovecot (Debian:12) 1:2.3.19.1+dfsg1-2.1+deb12u6; dovecot (Debian:13) 1:2.4.1+dfsg1-6+deb13u6.

Low priority for now. Upgrade to dovecot (Alpine:v3.23) 2.4.4-r0; dovecot (Debian:12) 1:2.3.19.1+dfsg1-2.1+deb12u6; dovecot (Debian:13) 1:2.4.1+dfsg1-6+deb13u6 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

Attacker can use a specially crafted base64 exchange between Dovecot and Client to fake SCRAM TLS channel binding. This requires that the attacker is able to position itself between Dovecot and the client connection. If successful, the attacker can eavesdrop communications between Dovecot and client as MITM proxy. Install fixed version. No publicly available exploits are known.

Published
May 12, 2026
Updated
Oct 26, 2026
EPSS
0.2% · 11th percentile

Report tools

JSON

Action score

21

Monitor

Low priority for now.

CVSS
21 / 40 · 5.3 / 10
CISA KEV
0 / 30 · Not listed
EPSS
0 / 30 · 0.2%

CISA SSVC decision

Exploitation
none
Automatable
no
Technical impact
total

Vulnrichment: CISA's decision-tree inputs.

CNA vs NVD score

NVD
5.3
CNA · OX
6.8
1.5 point gap

CVSS:3.1/AV:A/AC:H/PR:N/UI:N/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-2026-33603

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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  • 10 scans an hour on the security tools, at most 30 a day (3 a day without an account), an API key and MCP
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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 3.1.0affected · semver
    • up to and including 2.4.0affected · semver

Affected versions

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

  • dovecot dovecotbefore 2.4.4
  • open-xchange dovecotbefore 3.1.5

Package-level exposure

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

EcosystemPackageAffected rangeFix
Alpine:v3.23dovecotbefore 2.4.4-r02.4.4-r0
Debian:12dovecotbefore 1:2.3.19.1+dfsg1-2.1+deb12u61:2.3.19.1+dfsg1-2.1+deb12u6
Debian:13dovecotbefore 1:2.4.1+dfsg1-6+deb13u61:2.4.1+dfsg1-6+deb13u6
Debian:14dovecotbefore 1:2.4.4+dfsg1-11:2.4.4+dfsg1-1
openSUSE:Leap 16.0dovecot24before 2.4.4-160000.1.12.4.4-160000.1.1
openSUSE:Tumbleweeddovecot24before 2.4.4-1.12.4.4-1.1
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 2.2.31-19.37.22.2.31-19.37.2
SUSE:Linux Enterprise Server 16.0dovecot24before 2.4.4-160000.1.12.4.4-160000.1.1

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-2026-27860Mar 27, 2026 · If auth_username_chars is empty, it is possible to inject arbitrary LDAP filter to Dovecot's LDAP authentication.
    21Monitor
  • ← EarlierCVE-2026-27851May 12, 2026 · When safe filter is used with variable expansion, all following pipelines on the same string are incorrectly interpreted as safe too…
    36Monitor
  • Later →CVE-2026-40016May 12, 2026 · Attacker can upload a malicious Sieve script over ManageSieve service (or locally) to bypass configured CPU time limits for Sieve up to 130…
    26Monitor

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:dovecot2.4.4-r0 · Alpine:v3.23Package registry (OSV)
debian:dovecot1:2.3.19.1+dfsg1-2.1+deb12u6 · Debian:12Package registry (OSV)
opensuse:dovecot242.4.4-1.1 · openSUSE:TumbleweedPackage registry (OSV)
suse:dovecot222.2.31-19.37.2 · 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:dovecot242.4.4-160000.1.1 · 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

  • Someone on the same network segment 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
Adjacent
Attack complexity
High
Privileges required
None
User interaction
None
Scope
Unchanged
Confidentiality impact
High
Integrity impact
None
Availability impact
None

Weakness class (CWE)

CWE-99 · Improper Control of Resource Identifiers ('Resource Injection')

CVSS vector

CVSS:3.1/AV:A/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.

ATT&CK techniques

—

References

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

All records