VulnerabilityPublished 11 Aug 2025

CVE-2025-53910: Mattermost Confluence Plugin · Missing Authorization

Affects Mattermost Confluence PluginSource CVE Database V5

Not known to be exploited · CVSS 4.0 Medium · fixed in 1.5.0 : update Mattermost Confluence Plugin when convenient.

Data as of 26 Oct 2026, 15:59 UTC

CVSS 3.1 base score

4.0Medium

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

EPSS: 0.1% chance of exploitation in 30 days – higher than 9% of CVEsExploit Prediction Scoring System: the likelihood attackers will use this flaw soon.
Patch: Available – fixed in 1.5.0

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

Attack Vector: Network
Attack Complexity: High
Privileges Required: None
User Interaction: None
Scope: Changed
Confidentiality: None
Integrity: Low
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: 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: 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: None: There is no loss of confidentiality within the impacted component.
Integrity: Low: Modification of data is possible, but the attacker does not have control over the consequence of a modification, or the amount of modification is limited. The data modification does not have a direct, serious impact on the impacted component.
Availability: None: There is no impact to availability within the impacted component.

Definitions: FIRST CVSS v3.1 specification.

Exploitation evidence

Disclosed: evidence found.
CVE published 11 Aug 2025
Detectable: no evidence on record.
No public nuclei template indexed
Weaponised: 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 26 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.
Weaponised: Public exploit code exists in Metasploit or Exploit-DB, 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

Affected software

Product	Affected	Fixed in
Mattermost Mattermost Confluence Plugin	Affected =0	Fixed in–

AI-suggested

European organizations should immediately assess their Mattermost Confluence Plugin versions and plan to upgrade to version 1.5.0 or later once available, as this version addresses the missing authorization checks. If you cannot patch yet, organizations can mitigate risk by restricting network access to the Mattermost API endpoints, especially the edit channel subscription API, using firewalls or API gateways to limit exposure. Implementing strict monitoring and logging of API calls related to channel subscriptions can help detect anomalous or unauthorized subscription creation attempts. Additionally, organizations should review and tighten access control policies within Mattermost and Confluence integrations, ensuring that only trusted users and systems have API access. Employing network segmentation to isolate Mattermost servers and enforcing multi-factor authentication for administrative access can further reduce risk. Finally, organizations should stay informed about updates from Mattermost and apply security patches promptly once released.

Description

Mattermost Confluence Plugin version <1.5.0 fails to check the access of the user to the channel which allows attackers to create a channel subscription without proper access to the channel via API call to the edit channel subscription endpoint.

Impact

For European organizations using Mattermost with the Confluence Plugin, this vulnerability could lead to unauthorized access to channel subscriptions, potentially exposing sensitive internal communications or project information. While the vulnerability does not directly compromise confidentiality, the ability to subscribe to channels without proper authorization could allow attackers to receive updates or notifications intended only for authorized users, indirectly leading to information leakage. This could be particularly impactful in sectors with strict data privacy regulations such as finance, healthcare, and government institutions across Europe. The integrity impact is low but still relevant, as unauthorized subscriptions could be used to manipulate or monitor communication flows. Given the network-based exploitation and no requirement for authentication, attackers could remotely exploit this vulnerability, increasing the risk of widespread abuse. The medium severity rating suggests that while the vulnerability is not critical, it poses a tangible risk that should not be ignored, especially in environments where Mattermost is used for sensitive collaboration. The lack of known exploits in the wild provides a window of opportunity for organizations to remediate before active exploitation occurs.

CWE-862Missing Authorization (opens in a new tab)
Class weaknessLikelihood of exploit: HighCWE Top 25 (2025): #4OWASP Top 10 A01:2025: Broken Access Control (opens in a new tab)
The product does not perform an authorization check when an actor attempts to access a resource or perform an action.
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)
Attack patterns
Exploitation of Thunderbolt Protection Flaws (opens in a new tab)
From MITRE CWE, MITRE CAPEC and OWASP (Top 10, OpenCRE).

References

mattermost.com/security-updates (opens in a new tab)

Community reviews

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Exploitation evidence

What to do

Affected software

Description

AI analysisMachine-generated, updated 11 Aug 2025, 19:35 UTC

WeaknessesCWE-862

Technical details

References

Community reviews

Related threats