CVE-2026-21388 json
Unbounded Request Body Read in MS Teams Plugin {{/lifecycle}} Webhook Endpoint
published 2026-04-09 7 mo ago modified 2026-06-25 4 mo ago also GHSA-x274-8qfc-hrgf , GO-2026-5734 , EUVD-2026-20880
- cvss
- 3.7
- 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 Plugins versions <=2.3.1 fail to limit the request body size on the {{/lifecycle}} webhook endpoint which allows an authenticated attacker to cause memory exhaustion and denial of service via sending an oversized JSON payload. Mattermost Advisory ID: MMSA-2026-00610
Patch / fix
- go github.com/mattermost/mattermost-plugin-msteams 1.15.1-0.20260213190728-6fe4d295592e
- Mattermost Mattermost 2.3.2.0
- 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
0.32% 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 | 3.7 | CVSS:3.1/AV:N/AC:H/PR:N/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 | 3.7 | CVSS:3.1/AV:N/AC:H/PR:N/UI:N/S:U/C:N/I:N/A:L |
Affected packages
| ecosystem | package | affected | fixed in |
|---|---|---|---|
| go | github.com/mattermost/mattermost-plugin-msteams | <1.15.1-0.20260213190728-6fe4d295592e |
1.15.1-0.20260213190728-6fe4d295592e |
Affected products
- Mattermost Mattermost
Classification
- Weakness
-
- CWE-770 Allocation of Resources Without Limits or Throttling
References
-
github.com
/mattermost/mattermost-plugin-msteams/commit/6fe4d295592ecc8767d67e69286cbeec01be3210
web, patch
-
mattermost.com
/security-updates
vendor-advisory, web
-
nvd.nist.gov
/vuln/detail/CVE-2026-21388
advisory
-
github.com
/mattermost/mattermost-plugin-msteams
package
-
github.com
/mattermost/mattermost-plugin-msteams/releases/tag/v2.3.2
web
-
github.com
/advisories/GHSA-x274-8qfc-hrgf
advisory
Sources
- CVE List CVE-2026-21388
- GitHub Advisory GHSA-x274-8qfc-hrgf
- NVD CVE-2026-21388
- OSV GO-2026-5734
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.