CVE-2026-27856
published 2026-03-27CVE-2026-27856: Doveadm credentials are verified using direct comparison which is susceptible to timing oracle attack. An attacker can use this to determine the configured…
PriorityP335medium5.9CVSS 3.1
AVNACHPRNUINSUCHINAN
EPSS
0.39%
31.8th percentile
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.
Affected
12 ranges
| Vendor | Product | Version range | Fixed in |
|---|---|---|---|
| debian | dovecot | < dovecot 1:2.3.19.1+dfsg1-2.1+deb12u2 (bookworm) | dovecot 1:2.3.19.1+dfsg1-2.1+deb12u2 (bookworm) |
| dovecot | dovecot | < 2.4.3 | 2.4.3 |
| dovecot | dovecot | >= 0 < 1:2.3.19.1+dfsg1-2.1+deb12u2 | 1:2.3.19.1+dfsg1-2.1+deb12u2 |
| dovecot | dovecot | >= 0 < 1:2.4.1+dfsg1-6+deb13u4 | 1:2.4.1+dfsg1-6+deb13u4 |
| dovecot | dovecot | >= 0 < 1:2.3.16+dfsg1-3ubuntu2.7 | 1:2.3.16+dfsg1-3ubuntu2.7 |
| dovecot | dovecot | >= 0 < 1:2.3.21+dfsg1-2ubuntu6.3 | 1:2.3.21+dfsg1-2ubuntu6.3 |
| dovecot | dovecot | >= 0 < 1:2.4.1+dfsg1-5ubuntu4.1 | 1:2.4.1+dfsg1-5ubuntu4.1 |
| open-xchange | dovecot | < 2.3.22.1 | 2.3.22.1 |
| open-xchange | dovecot | >= 3.0.0 < 3.0.5 | 3.0.5 |
| open-xchange | dovecot | >= 3.1.0 < 3.1.4 | 3.1.4 |
| open-xchange_gmbh | ox_dovecot_pro | <= 2.3.0 | — |
| ubuntu | dovecot | — | — |
CVSS provenance
nvdv3.15.9MEDIUMCVSS:3.1/AV:N/AC:H/PR:N/UI:N/S:U/C:H/I:N/A:N
osv7.4HIGH
vendor_debian7.4HIGH
vendor_redhat7.4HIGH
vendor_ubuntu5.3MEDIUM
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Ubuntu
Dovecot regression
vendor_ubuntu·2026-04-28·CVSS 5.3
CVE-2026-0394 [MEDIUM] Dovecot regression
Title: Dovecot regression
Summary: USN-8136-1 introduced a regression in Dovecot
USN-8136-1 fixed vulnerabilities in Dovecot. The update caused a regression
on Ubuntu 22.04 LTS and Ubuntu 24.04 LTS. This update fixes the problem.
We apologize for the inconvenience.
Original advisory details:
It was discovered that Dovecot incorrectly handled invalid base64 SASL data.
An attacker could possibly use this issue to cause a denial of service. This
issue only affected Ubuntu 25.10. (CVE-2025-59028)
It was discovered that Dovecot script decode2text.sh incorrectly handled zip
files. An attacker could possibly use this issue to obtain sensitive
information. (CVE-2025-59031)
It was discovered that Dovecot incorrectly handled certain AUTHENTICATE
requests. An attacker could possibly use this i
Ubuntu
Dovecot vulnerabilities
vendor_ubuntu·2026-03-31·CVSS 5.3
CVE-2026-27857 [MEDIUM] Dovecot vulnerabilities
Title: Dovecot vulnerabilities
Summary: Several security issues were fixed in Dovecot.
It was discovered that Dovecot incorrectly handled invalid base64 SASL data.
An attacker could possibly use this issue to cause a denial of service. This
issue only affected Ubuntu 25.10. (CVE-2025-59028)
It was discovered that Dovecot script decode2text.sh incorrectly handled zip
files. An attacker could possibly use this issue to obtain sensitive
information. (CVE-2025-59031)
It was discovered that Dovecot incorrectly handled certain AUTHENTICATE
requests. An attacker could possibly use this issue to cause a denial of
service. (CVE-2025-59032)
It was discovered that Dovecot incorrectly handled certain SQL based
authentication. An attacker could possibly use this issue to bypass
authentication. Thi
Red Hat
dovecot: Doveadm: Full access via timing oracle attack in credential verification
vendor_redhat·2026-03-27·CVSS 7.4
CVE-2026-27856 [HIGH] CWE-208 dovecot: Doveadm: Full access via timing oracle attack in credential verification
dovecot: Doveadm: Full access via timing oracle attack in credential verification
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.
A flaw was found in Doveadm, a component of Dovecot. An attacker can exploit a timing oracle vulnerability during the direct comparison of credentials. This allows the attacker to determine the configured credentials, potentially leading to full unauthorized access to the affected component.
Package: dovecot (Red Hat Enterprise Linux 10) - Not affect
Debian
CVE-2026-27856: dovecot - Doveadm credentials are verified using direct comparison which is susceptible to...
vendor_debian·2026·CVSS 7.4
CVE-2026-27856 [HIGH] CVE-2026-27856: dovecot - Doveadm credentials are verified using direct comparison which is susceptible to...
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.
Scope: local
bookworm: resolved (fixed in 1:2.3.19.1+dfsg1-2.1+deb12u2)
bullseye: open
forky: open
sid: resolved (fixed in 1:2.4.3+dfsg1-1)
trixie: resolved (fixed in 1:2.4.1+dfsg1-6+deb13u4)
VulDB
Open-Xchange OX Dovecot Pro up to 2.3.0 Doveadm Http Service improper authentication (adv-2026-0001 / Nessus ID 304114)
vuldb·2026-07-01·CVSS 5.9
CVE-2026-27856 [MEDIUM] Open-Xchange OX Dovecot Pro up to 2.3.0 Doveadm Http Service improper authentication (adv-2026-0001 / Nessus ID 304114)
A vulnerability was found in Open-Xchange OX Dovecot Pro up to 2.3.0. It has been rated as critical. The affected element is an unknown function of the component Doveadm Http Service. The manipulation leads to improper authentication.
This vulnerability is listed as CVE-2026-27856. The attack may be initiated remotely. There is no available exploit.
Upgrading the affected component is advised.
OSV
dovecot vulnerabilities
osv·2026-03-31·CVSS 5.3
CVE-2025-59028 [MEDIUM] dovecot vulnerabilities
dovecot vulnerabilities
It was discovered that Dovecot incorrectly handled invalid base64 SASL data.
An attacker could possibly use this issue to cause a denial of service. This
issue only affected Ubuntu 25.10. (CVE-2025-59028)
It was discovered that Dovecot script decode2text.sh incorrectly handled zip
files. An attacker could possibly use this issue to obtain sensitive
information. (CVE-2025-59031)
It was discovered that Dovecot incorrectly handled certain AUTHENTICATE
requests. An attacker could possibly use this issue to cause a denial of
service. (CVE-2025-59032)
It was discovered that Dovecot incorrectly handled certain SQL based
authentication. An attacker could possibly use this issue to bypass
authentication. This issue only affected Ubuntu 25.10. (CVE-2026-24031)
It was dis
GHSA
GHSA-mv3x-9fw3-qf38: Doveadm credentials are verified using direct comparison which is susceptible to timing oracle attack
ghsa_unreviewed·2026-03-27
CVE-2026-27856 [HIGH] CWE-287 GHSA-mv3x-9fw3-qf38: Doveadm credentials are verified using direct comparison which is susceptible to timing oracle attack
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.
OSV
CVE-2026-27856: Doveadm credentials are verified using direct comparison which is susceptible to timing oracle attack
osv·2026-03-27·CVSS 7.4
CVE-2026-27856 [HIGH] CVE-2026-27856: Doveadm credentials are verified using direct comparison which is susceptible to timing oracle attack
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.
No detection rules found.
No public exploits indexed.
Wiz
CVE-2026-27858 Impact, Exploitability, and Mitigation Steps | Wiz
blogs_wiz·CVSS 7.4
CVE-2026-27858 [HIGH] CVE-2026-27858 Impact, Exploitability, and Mitigation Steps | Wiz
## CVE-2026-27858 :
Dovecot vulnerability analysis and mitigation
Attacker can send a specifically crafted message before authentication that causes managesieve to allocate large amount of memory.
Attacker can force managesieve-login to be unavailable by repeatedly crashing the process. Protect access to managesieve protocol, or install fixed version. No publicly available exploits are known.
Source : NVD
## 7.5
Score
Published March 27, 2026
Severity HIGH
CNA Score 7.5
Affected Technologies
Dovecot
Linux Red Hat
Has Public Exploit No
Has CISA KEV Exploit No
CISA KEV Release Date N/A
CISA KEV Due Date N/A
Exploitation Probability Percentile (EPSS) 17.5
Exploitation Probability (EPSS) 0.1
Affected packages and libraries
dovecot
dovecot-devel
Sources
NVD
Debian 11, 1
Wiz
CVE-2026-0394 Impact, Exploitability, and Mitigation Steps | Wiz
blogs_wiz·CVSS 5.3
CVE-2026-0394 [MEDIUM] CVE-2026-0394 Impact, Exploitability, and Mitigation Steps | Wiz
## CVE-2026-0394 :
Dovecot vulnerability analysis and mitigation
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 to allowed characters, path traversal can happen if the domain component is directory partial. This allows inadvertently reading /etc/passwd (or some other path which ends with passwd). If this file contains passwords, it can be used to authenticate wrongly, or if this is userdb, it can unexpectly make system users appear valid users. Upgrade to fixed version, or use different authentication scheme that does not rely on paths. Alternatively you can also ensure that the per-domain passwd files are in some other location, such as /etc/dovecot/auth/%d. No publicly available exploits are kn
Wiz
CVE-2026-27856 Impact, Exploitability, and Mitigation Steps | Wiz
blogs_wiz·CVSS 7.4
CVE-2026-27856 [HIGH] CVE-2026-27856 Impact, Exploitability, and Mitigation Steps | Wiz
## CVE-2026-27856 :
Dovecot vulnerability analysis and mitigation
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 : NVD
## 7.4
Score
Published March 27, 2026
Severity HIGH
CNA Score 7.4
Affected Technologies
Dovecot
Linux Red Hat
Has Public Exploit No
Has CISA KEV Exploit No
CISA KEV Release Date N/A
CISA KEV Due Date N/A
Exploitation Probability Percentile (EPSS) 11.8
Exploitation Probability (EPSS) N/A
Affected packages and libraries
dovecot-pgsql
do
Wiz
CVE-2026-27855 Impact, Exploitability, and Mitigation Steps | Wiz
blogs_wiz·CVSS 6.8
CVE-2026-27855 [MEDIUM] CVE-2026-27855 Impact, Exploitability, and Mitigation Steps | Wiz
## CVE-2026-27855 :
Dovecot vulnerability analysis and mitigation
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.
Source : NVD
## 6.8
Score
Published March 27, 2026
Severity MEDIUM
CNA Score 6.8
Affected Technologies
Dovecot
Linux Red Hat
Has Public Exploit No
Has CISA KEV Exploit No
CISA KEV Release Date N/A
CISA KEV Due Dat
Wiz
CVE-2025-59032 Impact, Exploitability, and Mitigation Steps | Wiz
blogs_wiz·CVSS 7.5
CVE-2025-59032 [HIGH] CVE-2025-59032 Impact, Exploitability, and Mitigation Steps | Wiz
## CVE-2025-59032 :
Dovecot vulnerability analysis and mitigation
ManageSieve AUTHENTICATE command crashes when using literal as SASL initial response. This can be used to crash ManageSieve service repeatedly, making it unavailable for other users. Control access to ManageSieve port, or disable the service if it's not needed. Alternatively upgrade to a fixed version. No publicly available exploits are known.
Source : NVD
## 7.5
Score
Published March 27, 2026
Severity HIGH
CNA Score 7.5
Affected Technologies
Dovecot
Linux Red Hat
Has Public Exploit No
Has CISA KEV Exploit No
CISA KEV Release Date N/A
CISA KEV Due Date N/A
Exploitation Probability Percentile (EPSS) 21.3
Exploitation Probability (EPSS) 0.1
Affected packages and libraries
dovecot
dovecot-devel
Sources
N
Wiz
CVE-2026-27860 Impact, Exploitability, and Mitigation Steps | Wiz
blogs_wiz·CVSS 7.4
CVE-2026-27860 [HIGH] CVE-2026-27860 Impact, Exploitability, and Mitigation Steps | Wiz
## CVE-2026-27860 :
Dovecot vulnerability analysis and mitigation
If auth_username_chars is empty, it is possible to inject arbitrary LDAP filter to Dovecot's LDAP authentication. This leads to potentially bypassing restrictions and allows probing of LDAP structure. Do not clear out auth_username_chars, or install fixed version. No publicly available exploits are known.
Source : NVD
## 3.7
Score
Published March 27, 2026
Severity LOW
CNA Score 3.7
Affected Technologies
Dovecot
Linux Red Hat
Has Public Exploit No
Has CISA KEV Exploit No
CISA KEV Release Date N/A
CISA KEV Due Date N/A
Exploitation Probability Percentile (EPSS) 17.7
Exploitation Probability (EPSS) 0.1
Affected packages and libraries
dovecot-pigeonhole
dovecot
Sources
NVD
Alpine 3.23 Severity LOW Has Fi
Wiz
CVE-2025-59028 Impact, Exploitability, and Mitigation Steps | Wiz
blogs_wiz·CVSS 5.3
CVE-2025-59028 [MEDIUM] CVE-2025-59028 Impact, Exploitability, and Mitigation Steps | Wiz
## CVE-2025-59028 :
Dovecot vulnerability analysis and mitigation
When sending invalid base64 SASL data, login process is disconnected from the auth server, causing all active authentication sessions to fail. Invalid BASE64 data can be used to DoS a vulnerable server to break concurrent logins. Install fixed version or disable concurrency in login processes (heavy perfomance penalty on large deployments). No publicly available exploits are known.
Source : NVD
## 5.3
Score
Published March 27, 2026
Severity MEDIUM
CNA Score 5.3
Affected Technologies
Dovecot
Linux Red Hat
Has Public Exploit No
Has CISA KEV Exploit No
CISA KEV Release Date N/A
CISA KEV Due Date N/A
Exploitation Probability Percentile (EPSS) 27
Exploitation Probability (EPSS) 0.1
Affected packages and librar
Wiz
CVE-2026-27859 Impact, Exploitability, and Mitigation Steps | Wiz
blogs_wiz·CVSS 7.4
CVE-2026-27859 [HIGH] CVE-2026-27859 Impact, Exploitability, and Mitigation Steps | Wiz
## CVE-2026-27859 :
Dovecot vulnerability analysis and mitigation
A mail message containing excessive amount of RFC 2231 MIME parameters causes LMTP to use too much CPU. A suitably formatted mail message causes mail delivery process to consume large amounts of CPU time. Use MTA capabilities to limit RFC 2231 MIME parameters in mail messages, or upgrade to fixed version where the processing is limited. No publicly available exploits are known.
Source : NVD
## 5.3
Score
Published March 27, 2026
Severity MEDIUM
CNA Score 5.3
Affected Technologies
Dovecot
Linux Red Hat
Has Public Exploit No
Has CISA KEV Exploit No
CISA KEV Release Date N/A
CISA KEV Due Date N/A
Exploitation Probability Percentile (EPSS) 15.8
Exploitation Probability (EPSS) 0.1
Affected packages and librarie
Wiz
CVE-2026-24031 Impact, Exploitability, and Mitigation Steps | Wiz
blogs_wiz·CVSS 7.7
CVE-2026-24031 [HIGH] CVE-2026-24031 Impact, Exploitability, and Mitigation Steps | Wiz
## CVE-2026-24031 :
Dovecot vulnerability analysis and mitigation
Dovecot SQL based authentication can be bypassed when auth_username_chars is cleared by admin. This vulnerability allows bypassing authentication for any user and user enumeration. Do not clear auth_username_chars. If this is not possible, install latest fixed version. No publicly available exploits are known.
Source : NVD
## 7.7
Score
Published March 27, 2026
Severity HIGH
CNA Score 7.7
Affected Technologies
Dovecot
Linux Red Hat
Has Public Exploit No
Has CISA KEV Exploit No
CISA KEV Release Date N/A
CISA KEV Due Date N/A
Exploitation Probability Percentile (EPSS) 20
Exploitation Probability (EPSS) 0.1
Affected packages and libraries
dovecot
dovecot-devel
Sources
NVD
Alpine 3.23 Severity HIGH Has Fi
Wiz
CVE-2025-59031 Impact, Exploitability, and Mitigation Steps | Wiz
blogs_wiz·CVSS 4.3
CVE-2025-59031 [MEDIUM] CVE-2025-59031 Impact, Exploitability, and Mitigation Steps | Wiz
## CVE-2025-59031 :
Dovecot vulnerability analysis and mitigation
Dovecot has provided a script to use for attachment to text conversion. This script unsafely handles zip-style attachments. Attacker can use specially crafted OOXML documents to cause unintended files on the system to be indexed and subsequently ending up in FTS indexes. Do not use the provided script, instead, use something else like FTS tika. No publicly available exploits are known.
Source : NVD
## 4.3
Score
Published March 27, 2026
Severity MEDIUM
CNA Score 4.3
Affected Technologies
Dovecot
Linux Red Hat
Has Public Exploit No
Has CISA KEV Exploit No
CISA KEV Release Date N/A
CISA KEV Due Date N/A
Exploitation Probability Percentile (EPSS) 8.6
Exploitation Probability (EPSS) N/A
Affected packages and l
Wiz
CVE-2026-27857 Impact, Exploitability, and Mitigation Steps | Wiz
blogs_wiz·CVSS 4.3
CVE-2026-27857 [MEDIUM] CVE-2026-27857 Impact, Exploitability, and Mitigation Steps | Wiz
## CVE-2026-27857 :
Dovecot vulnerability analysis and mitigation
Sending "NOOP (((...)))" command with 4000 parenthesis open+close results in ~1MB extra memory usage. Longer commands will result in client disconnection. This 1 MB can be left allocated for longer time periods by not sending the command ending LF. So attacker could connect possibly from even a single IP and create 1000 connections to allocate 1 GB of memory, which would likely result in reaching VSZ limit and killing the process and its other proxied connections. Attacker could connect possibly from even a single IP and create 1000 connections to allocate 1 GB of memory, which would likely result in reaching VSZ limit and killing the process and its other proxied connections. Install fixed version, there is no other remed
Bugzilla
CVE-2026-27856 dovecot: Doveadm: Full access via timing oracle attack in credential verification
bugzilla·2026-03-27·CVSS 7.4
CVE-2026-27856 [HIGH] CVE-2026-27856 dovecot: Doveadm: Full access via timing oracle attack in credential verification
CVE-2026-27856 dovecot: Doveadm: Full access via timing oracle attack in credential verification
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.
https://documentation.open-xchange.com/dovecot/security/advisories/csaf/2026/oxdc-adv-2026-0001.jsonhttps://access.redhat.com/errata/RHSA-2026:26564https://access.redhat.com/security/cve/CVE-2026-27856https://bugzilla.redhat.com/show_bug.cgi?id=2452171https://security.access.redhat.com/data/csaf/v2/vex/2026/cve-2026-27856.json
2026-03-27
Published