CVE-2026-61910VulnerabilityPublished 09/09/2026Updated 09/14/2026

CVE-2026-61910: CWE-863 Incorrect Authorization in cyrusimap Cyrus IMAP

Affects cyrusimap Cyrus IMAPSource CVE Database V5

Not known to be exploited · CVSS 3.5 Medium · fixed in 3.12.4 : update cyrusimap Cyrus IMAP when convenient.

Data as of 10/25/2026, 04:40:13 UTC

CVSS 3.1 base score

3.5Medium

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

Exploitation: Not in CISA KEV, no exploitation reported
EPSS: 0.1% chance of exploitation in 30 days – higher than 8% of CVEsExploit Prediction Scoring System: the likelihood attackers will use this flaw soon.
Patch: Available – fixed in 3.12.4

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

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

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: High: A successful attack depends on conditions beyond the attacker's control. That is, a successful attack cannot be accomplished at will, but requires the attacker to invest in some measurable amount of effort in preparation or execution against the vulnerable component before a successful attack can be expected. For example, a successful attack may require an attacker to: gather knowledge about the environment in which the vulnerable target/component exists; prepare the target environment to improve exploit reliability; or inject themselves into the logical network path between the target and the resource requested by the victim in order to read and/or modify network communications (e.g., a man in the middle attack).
Privileges Required: Low: The attacker is authorized with (i.e., requires) privileges that provide basic user capabilities that could normally affect only settings and files owned by a user. Alternatively, an attacker with Low privileges may have the ability to cause an impact only to non-sensitive resources.
User Interaction: None: The vulnerable system can be exploited without any interaction from any user.
Scope: Changed: An exploited vulnerability can affect resources beyond the security scope managed by the security authority of the vulnerable component. In this case, the vulnerable component and the impacted component are different and managed by different security authorities.
Confidentiality: Low: There is some loss of confidentiality. Access to some restricted information is obtained, but the attacker does not have control over what information is obtained, or the amount or kind of loss is limited. The information disclosure does not cause a direct, serious loss to the impacted component.
Integrity: None: There is no loss of integrity within the impacted component.
Availability: None: There is no impact to availability within the impacted component.

Definitions: FIRST CVSS v3.1 specification.

What to do

Affected software

Product	Affected	Fixed in
cyrusimapCyrus IMAP	Affected <3.8.8 >=3.9.0 <3.10.4 >=3.11.0 <3.12.4	Fixed in 3.8.8 3.10.4 3.12.4

AI-suggested

A fix is available in Cyrus IMAP version 3.12.4. Users should upgrade to version 3.12.4 or later to remediate this issue. No other specific mitigations are indicated by the vendor advisory.

Description

CVE-2026-61910 is an authorization vulnerability in Cyrus IMAP before version 3.12.4. It allows an authenticated user with maySetKeywords permission on another user's mailbox to change the special-use role annotation of a shared mailbox. This could result in the sharee modifying the mailbox role to archived, snoozed, or other roles, potentially causing mail to be written to the shared mailbox and exposing more content than intended. The situation is considered unusual and is further mitigated by role duplication suppression if the target mailbox already has a non-shared mailbox with that role.

Impact

The vulnerability allows a sharee with limited permissions to change special-use mailbox roles on shared mailboxes, which might lead to mail being routed to the shared mailbox and exposing more content than intended. The impact is limited by the unusual nature of the scenario and role duplication suppression mechanisms. The CVSS score of 3.5 (medium severity) reflects low confidentiality impact, no integrity or availability impact, and requires network access with low privileges and high attack complexity.

Weaknesses

CWE-863Incorrect Authorization (opens in a new tab)
Class weaknessLikelihood of exploit: HighCWE Top 25 (2025): #17OWASP Top 10 A01:2025: Broken Access Control (opens in a new tab)
The product performs an authorization check when an actor attempts to access a resource or perform an action, but it does not correctly perform the check.
Architecture and Design
Divide the product into anonymous, normal, privileged, and administrative areas. Reduce the attack surface by carefully mapping roles with data and functionality. Use role-based access control (RBAC) to enforce the roles at the appropriate boundaries.
Architecture and Design
Ensure that access control checks are performed related to the business logic. These checks may be different than the access control checks that are applied to more generic resources such as files, connections, processes, memory, and database records.
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.
OWASP Cheat Sheets
Authorization (opens in a new tab)
OWASP ASVS 4.0.3
V8.3.8 (opens in a new tab)
V13.4.2 (opens in a new tab)
V7.2.2 (opens in a new tab)
From MITRE CWE, MITRE CAPEC and OWASP (Top 10, OpenCRE).

References

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