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Mattermost makes Use of Weak Hash

Moderate severity GitHub Reviewed Published Sep 15, 2025 to the GitHub Advisory Database • Updated Sep 16, 2025

Package

gomod github.com/mattermost/mattermost-server (Go)

Affected versions

>= 10.8.0, < 10.8.4
>= 10.5.0, < 10.5.9
>= 9.11.0, < 9.11.18
>= 10.10.0, < 10.10.2
>= 10.9.0, < 10.9.4

Patched versions

10.8.4
10.5.9
9.11.18
10.10.2
10.9.4
gomod github.com/mattermost/mattermost/server/v8 (Go)
< 8.0.0-20250718075842-cd87e5c87737
8.0.0-20250718075842-cd87e5c87737

Description

Mattermost versions 10.8.x <= 10.8.3, 10.5.x <= 10.5.8, 9.11.x <= 9.11.17, 10.10.x <= 10.10.1, 10.9.x <= 10.9.3 fail to properly validate cache keys for link metadata which allows authenticated users to access unauthorized posts and poison link previews via hash collision attacks on FNV-1 hashing.

References

Published by the National Vulnerability Database Sep 15, 2025
Published to the GitHub Advisory Database Sep 15, 2025
Reviewed Sep 16, 2025
Last updated Sep 16, 2025

Severity

Moderate

CVSS overall score

This score calculates overall vulnerability severity from 0 to 10 and is based on the Common Vulnerability Scoring System (CVSS).
/ 10

CVSS v3 base metrics

Attack vector
Network
Attack complexity
Low
Privileges required
Low
User interaction
None
Scope
Unchanged
Confidentiality
Low
Integrity
None
Availability
None

CVSS v3 base metrics

Attack vector: More severe the more the remote (logically and physically) an attacker can be in order to exploit the vulnerability.
Attack complexity: More severe for the least complex attacks.
Privileges required: More severe if no privileges are required.
User interaction: More severe when no user interaction is required.
Scope: More severe when a scope change occurs, e.g. one vulnerable component impacts resources in components beyond its security scope.
Confidentiality: More severe when loss of data confidentiality is highest, measuring the level of data access available to an unauthorized user.
Integrity: More severe when loss of data integrity is the highest, measuring the consequence of data modification possible by an unauthorized user.
Availability: More severe when the loss of impacted component availability is highest.
CVSS:3.1/AV:N/AC:L/PR:L/UI:N/S:U/C:L/I:N/A:N

EPSS score

Exploit Prediction Scoring System (EPSS)

This score estimates the probability of this vulnerability being exploited within the next 30 days. Data provided by FIRST.
(2nd percentile)

Weaknesses

Use of Weak Hash

The product uses an algorithm that produces a digest (output value) that does not meet security expectations for a hash function that allows an adversary to reasonably determine the original input (preimage attack), find another input that can produce the same hash (2nd preimage attack), or find multiple inputs that evaluate to the same hash (birthday attack). Learn more on MITRE.

CVE ID

CVE-2025-9078

GHSA ID

GHSA-9p92-x77w-9fw2

Source code

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