CVE-2026-26233 json
Denial of Service via HTTP/2 single packet attack on login endpoint
published 2026-03-25 7 mo ago modified 2026-06-17 4 mo ago also GHSA-247x-7qw8-fp98 , GO-2026-4916 , EUVD-2026-15756
- cvss
- 4.3
- version 3.1, CNA
- cisa kev
- Not listed
- not in CISA's catalog
- epss
- 0.3%
- EPSS 0.3% chance of exploitation in 30 days, percentile 24%
- public exploits
- 0
- none known
Summary
Mattermost versions 11.4.x <= 11.4.0, 11.3.x <= 11.3.1, 11.2.x <= 11.2.3, 10.11.x <= 10.11.11 fail to rate limit login requests which allows unauthenticated remote attackers to cause denial of service (server crash and restart) via HTTP/2 single packet attack with 100+ parallel login requests.. Mattermost Advisory ID: MMSA-2025-00566
Patch / fix
- go github.com/mattermost/mattermost-server 10.11.12, 10.11.12+incompatible, 11.2.4, 11.2.4+incompatible, 11.3.2, 11.3.2+incompatible, 11.4.1, 11.4.1+incompatible
- Mattermost Mattermost 10.11.12, 11.2.4, 11.3.2, 11.4.1, 11.5.0
- govulncheck-vulndb openSUSE Leap 15.6 0.0.20260402T184258-150000.1.158.1
suse advisories SUSE-SU-2026:1205-1
- govulncheck-vulndb openSUSE Leap 16.0 0.0.20260723T184607-160000.1.1
opensuse advisories openSUSE-SU-2026:21483-1
CISA SSVC
- Exploitation
- none
- Automatable
- no
- Technical impact
- partial
- Assessed
- 7 mo ago
Exploit prediction
0.31% chance of exploitation in the next 30 days, higher than 24% of all scored CVEs (FIRST EPSS, 2026-11-08).
CVSS scores
| assigned by | version | score | vector |
|---|---|---|---|
| CNA | 3.1 | 4.3 | CVSS:3.1/AV:N/AC:L/PR:L/UI:N/S:U/C:N/I:N/A:L |
| NVD | 3.1 | 6.5 | CVSS:3.1/AV:N/AC:L/PR:L/UI:N/S:U/C:N/I:N/A:H |
| GitHub | 3.1 | 4.3 | CVSS:3.1/AV:N/AC:L/PR:L/UI:N/S:U/C:N/I:N/A:L |
Affected packages
| ecosystem | package | affected | fixed in |
|---|---|---|---|
| go | github.com/mattermost/mattermost-server | >=11.4.0-rc1, <11.4.1 >=11.3.0-rc1, <11.3.2 >=11.2.0-rc1, <11.2.4 >=10.11.0-rc1, <10.11.12 >=10.11.0-rc1+incompatible, <10.11.12+incompatible >=11.2.0-rc1+incompatible, <11.2.4+incompatible >=11.3.0-rc1+incompatible, <11.3.2+incompatible >=11.4.0-rc1+incompatible, <11.4.1+incompatible |
11.4.1 11.3.2 11.2.4 10.11.12 10.11.12+incompatible 11.2.4+incompatible 11.3.2+incompatible 11.4.1+incompatible |
Affected products
- Mattermost Mattermost
Classification
- Weakness
-
- CWE-400 Uncontrolled Resource Consumption
References
-
mattermost.com
/security-updates
vendor-advisory, web
-
nvd.nist.gov
/vuln/detail/CVE-2026-26233
advisory
-
github.com
/mattermost/mattermost
package
-
github.com
/advisories/GHSA-247x-7qw8-fp98
advisory
Sources
- CVE List CVE-2026-26233
- GitHub Advisory GHSA-247x-7qw8-fp98
- NVD CVE-2026-26233
- OSV GO-2026-4916
Fencer Vulns keeps one entry per vulnerability: the CVE id wins, then GHSA, and records that alias each other are merged, except that two CVEs always keep separate entries. The same data is available as JSON.