Mattermost Open Redirect vulnerability

Description

Mattermost versions 10.10.x <= 10.10.1, 10.5.x <= 10.5.9, 10.9.x <= 10.9.4 fail to validate the redirect_to parameter, allowing an attacker to craft a malicious link that, once a user authenticates with their SAML provider, could post the user’s cookies to an attacker-controlled URL.

Basic information

Type
reviewed
Severity
high
Advisory on GitHub
Open advisory ↗
Repository advisory
Source code
Browse source ↗
Published (advisory)
2025-09-15 12:31:25 UTC
Updated
2025-09-16 19:54:55 UTC
GitHub reviewed
2025-09-16 19:54:54 UTC
NVD published
2025-09-15

EPSS Score

Score Percentile
0.03% 9.40%

CVSS Scores

Base score Version Severity Vector
7.6 3.1
CVSS:3.1/AV:N/AC:L/PR:L/UI:R/S:U/C:H/I:H/A:L Click to expand
Attack vector (AV:N)
Could be attacked over the internet or any normal routed network—not just someone sitting at the machine.
Attack complexity (AC:L)
Once they can reach the bug, pulling it off is straightforward—no weird race conditions or rare setup.
Privileges required (PR:L)
A normal user session is enough; they don’t have to be admin.
User interaction (UI:R)
A real person has to do something—click, install, enable—otherwise it doesn’t land.
Scope (S:U)
Damage stays in the same “trust bubble” as the broken component—no big spill into unrelated systems.
Confidentiality (C:H)
Serious risk that confidential data gets exposed in a big way.
Integrity (I:H)
They could widely tamper with or forge data—trust in the data is badly hurt.
Availability (A:L)
Might cause slowdowns, glitches, or partial disruption—not a full brick.

Identifiers

CWEs

CWE id Name
CWE-601 URL Redirection to Untrusted Site ('Open Redirect')

Affected packages (4)

Vulnerable version ranges and first patched releases as published by GitHub.

Ecosystem Package Vulnerable range First patched Vulnerable functions
go github.com/mattermost/mattermost-server >= 10.10.0, < 10.10.2 10.10.2
go github.com/mattermost/mattermost-server >= 10.5.0, < 10.5.10 10.5.10
go github.com/mattermost/mattermost-server >= 10.9.0, < 10.9.5 10.9.5
go github.com/mattermost/mattermost/server/v8 < 8.0.0-20250731063404-9eebaadf8f72 8.0.0-20250731063404-9eebaadf8f72

References

cvelogic Threat Intelligence