Vulnerability · Published Mar 16, 2026 · Assigned by Mattermost
CVE-2026-24458DoS attack via login attempts with multi-megabyte passwords
High 7.5
In plain English
A high-severity resource allocation without limits in Mattermost from Mattermost. There are no confirmed reports of exploitation so far. The chance it is exploited in the next 30 days is estimated at 0.3% (higher than 22% of all known vulnerabilities). Fixed versions are available - upgrade the affected package.
Severity (CVSS 3.1)7.5High
Exploit odds (30 days)0.3%top 78.4% of all CVEs
Exploited in the wildNo reportsCISA SSVC: none
Attack toolingNoneno public tooling known
Official description
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
Affected packages & fixed versions
| Ecosystem | Package | Fixed in | Advisory |
|---|---|---|---|
| Go | github.com/mattermost/mattermost-server | 11.2.3 | GHSA-m5rv-56xx-hfc6 |
| Go | github.com/mattermost/mattermost-server | 5.3.2-0.20260129164748-7201f42d955f | GHSA-m5rv-56xx-hfc6 |
| Go | github.com/mattermost/mattermost-server | 10.11.11 | GHSA-m5rv-56xx-hfc6 |
| Go | github.com/mattermost/mattermost-server | 11.3.1 | GHSA-m5rv-56xx-hfc6 |
| Go | github.com/mattermost/mattermost-server | 10.11.11+incompatible, 11.2.3+incompatible, 11.3.1+incompatible | GO-2026-4731 |
| Go | github.com/mattermost/mattermost-server/v5 | no fix listed | GO-2026-4731 |
| Go | github.com/mattermost/mattermost-server/v6 | no fix listed | GO-2026-4731 |
| Go | github.com/mattermost/mattermost/server/v8 | 8.0.0-20260129164748-7201f42d955f | GO-2026-4731 |
| Go | github.com/mattermost/mattermost/server/v8 | 8.0.0-20260129164748-7201f42d955f | GHSA-m5rv-56xx-hfc6 |
Affected products (as reported)
| Vendor | Product | Versions |
|---|---|---|
| Mattermost | Mattermost | 11.3.0 – through 11.3.011.2.0 – through 11.2.210.11.0 – through 10.11.10 |
Weakness: CWE-770 · Vector: CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:N/I:N/A:H
References
- MMSA-2026-00587 vendor-advisory