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Mattermost CVE-2024-9155

MEDIUM
Incorrect Authorization (CWE-863)
2024-09-26 responsibledisclosure@mattermost.com
4.3
CVSS 3.1 · Vendor: mattermost
View

Vulnerability Assessment

Weakness
CWE
OWASP Top 10:2025
A01:2025 - Broken Access Control
ASVS 5.0
V8 - Authorization Authorization logic validation
MITRE ATT&CK

1 technique across 1 tactic: Privilege Escalation

The technique list with ATT&CK links and the kill-chain view is part of the Basic plan and up.

Impact

CVSS score of 4.3 (MEDIUM). Attack characteristics: network attack vector, low complexity, low privileges required, no user interaction not required.

Exploit ScenarioDerived

A remote attacker could bypass authorization checks to access restricted resources by sending crafted requests to the affected application.

This Month Plan within 30 days. Why: MEDIUM severity (CVSS 4.0-6.9).
No patch listed yet 0.3% exploitation probability (EPSS)

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AnalysisAI

Mattermost versions 9.10.x <= 9.10.1, 9.9.x <= 9.9.2, 9.5.x <= 9.5.8 fail to limit access to channels files that have not been linked to a post which allows an attacker to view them in channels that. Rated medium severity (CVSS 4.3), this vulnerability is remotely exploitable, low attack complexity. No vendor patch available.

RemediationAI

No vendor patch is available at time of analysis. Monitor vendor advisories for updates. Review and test authorization logic, implement consistent access control checks, use centralized authorization framework.

Affects your stack

Find out whether the stacks and servers you run are on an affected version.

Checking this CVE against your own stacks and servers is part of the Basic plan and up.

Technical ContextAI · show details

This vulnerability is classified as Incorrect Authorization (CWE-863), which allows attackers to bypass authorization checks to access restricted resources. Mattermost versions 9.10.x <= 9.10.1, 9.9.x <= 9.9.2, 9.5.x <= 9.5.8 fail to limit access to channels files that have not been linked to a post which allows an attacker to view them in channels that they are a member of. Affected products include: Mattermost Mattermost Server.

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  • Exploit and PoC references, threat intelligence from 22 sources

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Severity by source

Vendor (mattermost) PRIMARY 4.3 MEDIUM
AV:N/AC:L/PR:L/UI:N/S:U/C:L/I:N/A:N

Primary rating from Vendor (mattermost) · only source for this CVE.

CVSS VectorVendor: mattermost

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

DescriptionCVE.org

Mattermost versions 9.10.x <= 9.10.1, 9.9.x <= 9.9.2, 9.5.x <= 9.5.8 fail to limit access to channels files that have not been linked to a post which allows an attacker to view them in channels that they are a member of.

Threat Intelligence Overview

EPSS Score
0.3%
Top 83% exploitable
Data Quality
2 sources
Confidence: Low

How this decision was reached

The engine reads each signal below and applies a fixed list of rules from top to bottom. The first rule that matches sets the recommended action – like a statement, every line is shown.

SignalValue
Severity MEDIUM
CISA KEV No
Public POC No
EPSS 0.3%
Patch available No
Active threat No
Deciding rule
MEDIUM severity (CVSS 4.0-6.9)
What every action level means
Emergency Immediate action required. Criteria: CRITICAL + in CISA KEV (actively exploited) without patch, OR CRITICAL + EPSS > 30% without patch, OR CRITICAL + active threat signals without patch.
Act Now Prioritize within 24-48h. Criteria: in KEV with patch available, OR CRITICAL + public POC, OR HIGH + EPSS > 10%, OR CRITICAL + active threat, OR any CRITICAL severity.
This Week Schedule remediation this week. Criteria: HIGH severity (CVSS 7.0-8.9). Patch within normal change window.
This Month Plan within 30 days. Criteria: MEDIUM severity (CVSS 4.0-6.9), lower exploitation probability. Include in regular patch cycle.
Monitor Track and reassess. Criteria: LOW severity (CVSS 0.1-3.9), minimal exploitation risk. No immediate action needed.

SSVC AssessmentENISA

SSVC Decision· derived
Scheduled
Exploitation· derived
None
System Exposure· derived
Open
Automatable· derived
No
Human Impact· derived
Medium

Priority Score

22
Low Medium High Critical
KEV: 0
EPSS: 0
CVSS: +22
PoC: 0
Weaponized: 0
Threat intel: 0
Gov advisory: 0

Attack Technique

Authentication bypass attacks exploit flaws in the verification mechanisms that control access to systems and applications.

Affected Products (CPE)CVE.org

cpe:2.3:a:mattermost:mattermost_server:*:*:*:*:*:*:*:*
cpe:2.3:a:mattermost:mattermost_server:*:*:*:*:*:*:*:*
cpe:2.3:a:mattermost:mattermost_server:*:*:*:*:*:*:*:*
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