CVE-2026-27852VulnerabilityPublished 6 Oct 2026Updated 31 Oct 2026

Red Hat Security Advisory: dovecot security, bug fix, and enhancement update

Affects Red Hat dovecot security,Source GCVE Database

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Mentioned vulnerabilities

Authoritative record:CVE-2026-27852· High 7.5

Not known to be exploited · CVSS 7.5 High · fixed in Red Hat package updates : patch Red Hat dovecot security, soon.

Data as of 31 Oct 2026, 10:37 UTC

CVSS 3.1 base score

7.5High

How severe the flaw is on the 0–10 CVSS scale.

Patch: Available – fixed in 3.1.6, 3.0.7, 2.3.22.2 +1

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

Attack Vector: Network
Attack Complexity: Low
Privileges Required: None
User Interaction: None
Scope: Unchanged
Confidentiality: None
Integrity: None
Availability: High

Bold values are the worst case: easiest to exploit or largest impact.

Attack Vector: Network: The vulnerable component is bound to the network stack and the set of possible attackers extends beyond the other options listed, up to and including the entire Internet. Such a vulnerability is often termed 'remotely exploitable' and can be thought of as an attack being exploitable at the protocol level one or more network hops away (e.g., across one or more routers).
Attack Complexity: Low: Specialized access conditions or extenuating circumstances do not exist. An attacker can expect repeatable success against the vulnerable component.
Privileges Required: None: The attacker is unauthorized prior to attack, and therefore does not require any access to settings or files to carry out an attack.
User Interaction: None: The vulnerable system can be exploited without any interaction from any user.
Scope: Unchanged: An exploited vulnerability can only affect resources managed by the same security authority. In this case, the vulnerable component and the impacted component are either the same, or both are managed by the same security authority.
Confidentiality: None: There is no loss of confidentiality within the impacted component.
Integrity: None: There is no loss of integrity within the impacted component.
Availability: High: There is total loss of availability, resulting in the attacker being able to fully deny access to resources in the impacted component; this loss is either sustained (while the attacker continues to deliver the attack) or persistent (the condition persists even after the attack has completed). Alternatively, the attacker has the ability to deny some availability, but the loss of availability presents a direct, serious consequence to the impacted component (e.g., the attacker cannot disrupt existing connections, but can prevent new connections; the attacker can repeatedly exploit a vulnerability that, in each instance of a successful attack, leaks a only small amount of memory, but after repeated exploitation causes a service to become completely unavailable).

Definitions: FIRST CVSS v3.1 specification.

Exploitation evidence

Disclosed: evidence found.
CVE published 28 Aug 2026
Detectable: no evidence on record.
No public nuclei template indexed
Weaponized: no evidence on record.
No public exploit code indexed in Metasploit or Exploit-DB
Exploited in the wildExploited: no evidence on record.
Not in CISA KEV and no source reports exploitation
Observed by OffSeq MirageSeen by Mirage: no evidence on record.
No attack traffic recorded by OffSeq Mirage sensors

A missing step is not evidence of safety. Sources: cve.org (opens in a new tab), the Metasploit, Exploit-DB and nuclei-templates index as of 30 Oct 2026.

Disclosed: The CVE record is public on cve.org. Its publication is t = 0.
Detectable: A public nuclei template can find exposed instances, for defenders and attackers alike.
Weaponized: A Metasploit exploit module or Exploit-DB entry exists (Metasploit scanner modules do not count), or CISA SSVC or the CVSS exploit maturity reports a public proof of concept.
Exploited in the wild: CISA KEV lists it, CISA SSVC rates exploitation active, or a source reports attacks.
Observed by OffSeq Mirage: OffSeq Mirage honeypot sensors recorded attack traffic for this CVE, or found exposed hosts without attack traffic.

Moments are spaced evenly, not to scale; a dashed line marks a gap of six months or more. Deltas count from t = 0. Sources that give only a date (CISA KEV, Exploit-DB, or a time of exactly 00:00Z) read “same day” rather than hours. Metasploit modules carry the flaw’s disclosure date, not their release date, and nuclei templates carry no date, so both appear above but not on the timeline.

What to do

Upgrade OX Dovecot to 3.1.6, 3.0.7 or 2.3.22.2 (Pro); 2.4.5 (CE).

Affected software

Product	Affected	Fixed in
Open-Xchange GmbHOX Dovecot Pro	Affected >=3.1.0 <3.1.6	Fixed in 3.1.6
Open-Xchange GmbHOX Dovecot Pro	Affected >=3.0.0 <3.0.7	Fixed in 3.0.7
Open-Xchange GmbHOX Dovecot Pro	Affected >=2.3.0 <2.3.22.2	Fixed in 2.3.22.2
Open-Xchange GmbHOX Dovecot CE	Affected >=2.3.0 <2.4.5	Fixed in 2.4.5

Description

Dovecot is an IMAP server for Linux and other UNIX-like systems, written primarily with security in mind. It also contains a small POP3 server, and supports e-mail in either the maildir or mbox format. The SQL drivers and authentication plug-ins are provided as subpackages. Security Fix(es): * dovecot: Dovecot: Denial of Service via IMAP ID command with excessive parameters (CVE-2026-42391) * dovecot: Dovecot: Authentication bypass via incorrect OAuth2 token validation (CVE-2026-73208) * dovecot: Dovecot: Denial of service via crafted email headers (CVE-2026-27852) * dovecot: Dovecot: Denial of Service via truncated quoted argument in ManageSieve (CVE-2026-40019) * dovecot: Dovecot: Denial of Service and potential message duplication via connection limit exhaustion (CVE-2026-33263) * dovecot: Dovecot: Denial of Service in ManageSieve login process (CVE-2026-33605) * dovecot: Dovecot: Arbitrary Code Execution via Sieve editheader use-after-free (CVE-2026-42007) * dovecot: Dovecot: MySQL multi-byte escaping wrong (CVE-2026-40018) Bug Fix(es) and Enhancement(s): * Dovecot crashes when accessing mailbox with: "Panic: file mail-user.c: line 229 (mail_user_deinit): assertion failed: ((*user)->refcount == 1)" (JIRA:RHEL-176273) For more details about the security issue(s), including the impact, a CVSS score, acknowledgments, and other related information, refer to the CVE page(s) listed in the References section.

CWE-770Allocation of Resources Without Limits or Throttling (opens in a new tab)
Base weaknessLikelihood of exploit: HighCWE Top 25 (2025): #25
The product allocates a reusable resource or group of resources on behalf of an actor without imposing any intended restrictions on the size or number of resources that can be allocated.
Requirements
Clearly specify the minimum and maximum expectations for capabilities, and dictate which behaviors are acceptable when resource allocation reaches limits.
Architecture and Design
Limit the amount of resources that are accessible to unprivileged users. Set per-user limits for resources. Allow the system administrator to define these limits. Be careful to avoid CWE-410.
Architecture and Design
Design throttling mechanisms into the system architecture. The best protection is to limit the amount of resources that an unauthorized user can cause to be expended.
OWASP Cheat Sheets
Abuse Case (opens in a new tab)
OWASP ASVS 4.0.3
V8.1.4 (opens in a new tab)
V13.4.1 (opens in a new tab)
V11.1.4 (opens in a new tab)
Attack patterns
XML Ping of the Death (opens in a new tab)
Exponential Data Expansion (opens in a new tab)
Serialized Data Parameter Blowup (opens in a new tab)
Serialized Data with Nested Payloads (opens in a new tab)
Oversized Serialized Data Payloads (opens in a new tab)
From MITRE CWE, MITRE CAPEC and OWASP (Top 10, OpenCRE).
CWE-910Use of Expired File Descriptor (opens in a new tab)
Base weaknessLikelihood of exploit: Medium
The product uses or accesses a file descriptor after it has been closed.
CWE-1286Improper Validation of Syntactic Correctness of Input (opens in a new tab)
Base weakness
The product receives input that is expected to be well-formed - i.e., to comply with a certain syntax - but it does not validate or incorrectly validates that the input complies with the syntax.
Implementation · Input Validation
Assume all input is malicious. Use an "accept known good" input validation strategy, i.e., use a list of acceptable inputs that strictly conform to specifications. Reject any input that does not strictly conform to specifications, or transform it into something that does.
OWASP Cheat Sheets
XML Security (opens in a new tab)
Mass Assignment (opens in a new tab)
OWASP ASVS 4.0.3
V13.3.1 (opens in a new tab)
V5.1.4 (opens in a new tab)
V5.1.3 (opens in a new tab)
Attack patterns
SQL Injection (opens in a new tab)
NoSQL Injection (opens in a new tab)
From MITRE CWE, MITRE CAPEC and OWASP (Top 10, OpenCRE).
CWE-89Improper Neutralization of Special Elements used in an SQL Command (SQL Injection) (opens in a new tab)
Base weaknessLikelihood of exploit: HighCWE Top 25 (2025): #2OWASP Top 10 A05:2025: Injection (opens in a new tab)
The product constructs all or part of an SQL command using externally-influenced input from an upstream component, but it does not neutralize or incorrectly neutralizes special elements that could modify the intended SQL command when it is sent to a downstream component. Without sufficient removal or quoting of SQL syntax in user-controllable inputs, the generated SQL query can cause those inputs to be interpreted as SQL instead of ordinary user data.
Architecture and Design · Libraries or Frameworks
Use a vetted library or framework that does not allow this weakness to occur or provides constructs that make this weakness easier to avoid.
Architecture and Design · Parameterization
If available, use structured mechanisms that automatically enforce the separation between data and code. These mechanisms may be able to provide the relevant quoting, encoding, and validation automatically, instead of relying on the developer to provide this capability at every point where output is generated.
Architecture and Design · Operation · Environment Hardening
Run your code using the lowest privileges that are required to accomplish the necessary tasks. If possible, create isolated accounts with limited privileges that are only used for a single task. That way, a successful attack will not immediately give the attacker access to the rest of the software or its environment.
OWASP Cheat Sheets
Query Parameterization (opens in a new tab)
Unvalidated Redirects and Forwards (opens in a new tab)
XML Security (opens in a new tab)
XML External Entity Prevention (opens in a new tab)
File Upload (opens in a new tab)
OWASP ASVS 4.0.3
V5.3.4 (opens in a new tab)
V5.3.5 (opens in a new tab)
V1.5.1 (opens in a new tab)
Attack patterns
Command Line Execution through SQL Injection (opens in a new tab)
Object Relational Mapping Injection (opens in a new tab)
SQL Injection through SOAP Parameter Tampering (opens in a new tab)
Expanding Control over the Operating System from the Database (opens in a new tab)
SQL Injection (opens in a new tab)
From MITRE CWE, MITRE CAPEC and OWASP (Top 10, OpenCRE).
CWE-835Loop with Unreachable Exit Condition (Infinite Loop) (opens in a new tab)
Base weakness
The product contains an iteration or loop with an exit condition that cannot be reached, i.e., an infinite loop.
CWE-825Expired Pointer Dereference (opens in a new tab)
Base weakness
The product dereferences a pointer that contains a location for memory that was previously valid, but is no longer valid.
Architecture and Design
Choose a language that provides automatic memory management.
Implementation
When freeing pointers, be sure to set them to NULL once they are freed. However, the utilization of multiple or complex data structures may lower the usefulness of this strategy.
OWASP Cheat Sheets
XML Security (opens in a new tab)
Mass Assignment (opens in a new tab)
OWASP ASVS 4.0.3
V13.3.1 (opens in a new tab)
V5.1.4 (opens in a new tab)
V5.1.3 (opens in a new tab)
From MITRE CWE, MITRE CAPEC and OWASP (Top 10, OpenCRE).
CWE-303Incorrect Implementation of Authentication Algorithm (opens in a new tab)
Base weaknessOWASP Top 10 A07:2025: Authentication Failures (opens in a new tab)
The requirements for the product dictate the use of an established authentication algorithm, but the implementation of the algorithm is incorrect.
OWASP Cheat Sheets
OWASP Authentication (opens in a new tab)
OWASP ASVS 4.0.3
V2.8.5 (opens in a new tab)
V2.8.4 (opens in a new tab)
V9.2.3 (opens in a new tab)
Attack patterns
Reflection Attack in Authentication Protocol (opens in a new tab)
From MITRE CWE, MITRE CAPEC and OWASP (Top 10, OpenCRE).

References

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Exploitation evidence

What to do

Affected software

Description

WeaknessesCWE-770, CWE-910, CWE-1286 +4

Technical details

References

Community reviews

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