CVE-2026-24458

HIGH

Mattermost fails to properly handle very long passwords

Published March 16, 2026Updated March 23, 2026Source: osv

Summary

Mattermost versions 11.3.x <= 11.3.0, 11.2.x <= 11.2.2, 10.11.x <= 10.11.10 fail to properly handle very long passwords, which allows an attacker to overload the server CPU and memory via executing login attempts with multi-megabyte passwords. Mattermost Advisory ID: MMSA-2026-00587

Remediation

Upgrade to the fixed version using your package manager.

Update github.com/mattermost/mattermost/server/v8 to 8.0.0-20260129164748-7201f42d955f or later

go get github.com/mattermost/mattermost/server/v8@v8.0.0-20260129164748-7201f42d955f

Update github.com/mattermost/mattermost-server to 5.3.2-0.20260129164748-7201f42d955f or later

go get github.com/mattermost/mattermost-server@v5.3.2-0.20260129164748-7201f42d955f

Update github.com/mattermost/mattermost-server to 11.3.1 or later

go get github.com/mattermost/mattermost-server@v11.3.1

Update github.com/mattermost/mattermost-server to 10.11.11 or later

go get github.com/mattermost/mattermost-server@v10.11.11

Update github.com/mattermost/mattermost-server to 11.2.3 or later

go get github.com/mattermost/mattermost-server@v11.2.3

After upgrading, run your dependency scanner again to confirm the vulnerability is resolved.

Affected Packages (5)

Package	Ecosystem	Affected	Fixed In
github.com/mattermost/mattermost/server/v8	go	All versions	8.0.0-20260129164748-7201f42d955f
github.com/mattermost/mattermost-server	go	All versions	5.3.2-0.20260129164748-7201f42d955f
github.com/mattermost/mattermost-server	go	All versions	11.3.1
github.com/mattermost/mattermost-server	go	All versions	10.11.11
github.com/mattermost/mattermost-server	go	All versions	11.2.3

Vulnerability Classification

Common Weakness Enumeration (CWE) identifiers for this vulnerability type.

CWE-770
Allocation of Resources Without LimitsMITRE

CVSS Score Breakdown

What the CVSS (Common Vulnerability Scoring System) 7.5 score means for each attack dimension.

Attack Vector

Network

Attack Complexity

Low

Privileges Required

None

User Interaction

None

Scope

Unchanged

Confidentiality

None

Integrity

None

Availability

High

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

References

Frequently Asked Questions

What is CVE-2026-24458?: Mattermost fails to properly handle very long passwords This vulnerability has been assigned a severity rating of HIGH (CVSS score: 7.5/10).
How do I check if my project is affected by CVE-2026-24458?: CVE-2026-24458 affects github.com/mattermost/mattermost/server/v8 and github.com/mattermost/mattermost-server. Use GeekWala's free vulnerability scanner to check your dependencies against CVE-2026-24458 and 200,000+ other known vulnerabilities.

Severity & Exploitability

CVSS Score

7.5

High exploitability or significant impact. Prioritize remediation within days.

Also Known As

GHSA-m5rv-56xx-hfc6

GO-2026-4731

Related CVEs

CVE-2025-12419
CRITICAL
Mattermost fails to properly validate OAuth state tokens during OpenID Connect authentication
CVE-2025-12421
CRITICAL
Mattermost fails to to verify the token used during code exchange
CVE-2025-4981
CRITICAL
Mattermost allows authenticated users to write files to arbitrary locations
CVE-2026-3108
HIGH
Mattermost allows attackers to manipulate administrator terminals via crafted messages containing ANSI and OSC escape sequences
CVE-2025-58073
HIGH
Mattermost has a Missing Authorization vulnerability
CVE-2026-6346
HIGH
Mattermost doesn't sanitize sensitive configuration fields before including them in support packet generation
CVE-2025-58075
HIGH
Mattermost has a Missing Authorization vulnerability
CVE-2026-5740
HIGH
Mattermost doesn't properly validate msgpack-encoded WebSocket frames before memory allocation

Check if you're affected

Scan your dependencies to see if this vulnerability affects your projects.

Scan Your Dependencies