CVE-2026-4915

mediumpriority · track · 0EPSS 0.003 · 20 %ileEURUUS

grimoire priorityP3 · Track

Exploitable?

—

no known exploitation

Likely / severe?

0.28% (20th) EPSS

CVSS 6.5 · medium

Is it mine?

23 products

Check your exposure

Who says so?

5 sources

cnnvd · enisa_euvd · fstec_bdu · osv

EPSS · scored 2026-10-27

Mattermost versions 11.6.x <= 11.6.0, 11.5.x <= 11.5.3, 11.4.x <= 11.4.4, 10.11.x <= 10.11.14 fail to filter nil elements from outgoing webhook attachment payloads before processing, which allows an authenticated user to cause a denial of service (server process termination) via a crafted webhook callback response containing a null attachment entry.. Mattermost Advisory ID: MMSA-2026-00641

cvss

Technical severity, 0–10. One row per scoring source.

6.5

010

base score 0–10 · higher = more severe · hover a vector to decode

v3.16.5mediumAV:N/AC:L/PR:L/UI:N/S:U/C:N/I:N/A:Hsecondary · FSTEC (BDU) RU

v3.16.5mediumCVSS:3.1/AV:N/AC:L/PR:L/UI:N/S:U/C:N/I:N/A:Hsecondary · ENISA EU

v3.16.5mediumCVSS:3.1/AV:N/AC:L/PR:L/UI:N/S:U/C:N/I:N/A:Hsecondary · responsibledisclosure@mattermost.comexploitability 2.8 · impact 3.6

v3.16.5mediumCVSS:3.1/AV:N/AC:L/PR:L/UI:N/S:U/C:N/I:N/A:Hsecondary · OSV

v3.16mediumCVSS:3.1/AV:N/AC:L/PR:L/UI:N/S:U/C:N/I:N/A:H/E:Usecondary · CVSS-BT (t0sche)

ssvc

A stakeholder decision — act, attend, or track — from exploitation and impact.

Trackcoordinatorcisa_ssvcUS

weaknesses

The CWE weakness classes this flaw belongs to.

CWE-754USCWE-754USCWE-754US

affected products (23)

Products and version ranges known to be affected.

Mattermost Mattermost≤ 10.11.0 ≤10.11.14enisa_euvdEU
Mattermost Mattermost≤ 11.5.0 ≤11.5.3enisa_euvdEU
Mattermost Mattermost≤ 11.6.0 ≤11.6.0enisa_euvdEU
Mattermost Mattermost≤ 11.4.0 ≤11.4.4enisa_euvdEU
Mattermost Inc Mattermost10.11.0 → 10.11.14fstec_bduRU
Mattermost Inc Mattermost11.4.0 → 11.4.4fstec_bduRU
Mattermost Inc Mattermost11.5.0 → 11.5.3fstec_bduRU
Mattermost Inc Mattermost11.6.0 → 11.6.1fstec_bduRU
mattermost mattermost server10.11.0 → 10.11.15nvdUScpe:2.3:a:mattermost:mattermost_server:*:*:*:*:*:*:*:*
mattermost mattermost server11.4.0 → 11.4.5nvdUScpe:2.3:a:mattermost:mattermost_server:*:*:*:*:*:*:*:*
mattermost mattermost server11.5.0 → 11.5.4nvdUScpe:2.3:a:mattermost:mattermost_server:*:*:*:*:*:*:*:*
mattermost mattermost server11.6.0 → 11.6.1nvdUScpe:2.3:a:mattermost:mattermost_server:*:*:*:*:*:*:*:*
Go github.com/mattermost/mattermost-server10.11.0 → 10.11.15osvUSpkg:golang/github.com/mattermost/mattermost-server
Go github.com/mattermost/mattermost-server10.11.0+incompatible → 10.11.15+incompatibleosvUSpkg:golang/github.com/mattermost/mattermost-server
Go github.com/mattermost/mattermost-server11.4.0 → 11.4.5osvUSpkg:golang/github.com/mattermost/mattermost-server
Go github.com/mattermost/mattermost-server11.4.0+incompatible → 11.4.5+incompatibleosvUSpkg:golang/github.com/mattermost/mattermost-server
Go github.com/mattermost/mattermost-server11.5.0 → 11.5.4osvUSpkg:golang/github.com/mattermost/mattermost-server
Go github.com/mattermost/mattermost-server11.5.0+incompatible → 11.5.4+incompatibleosvUSpkg:golang/github.com/mattermost/mattermost-server
Go github.com/mattermost/mattermost-server11.6.0 → 11.6.1osvUSpkg:golang/github.com/mattermost/mattermost-server
Go github.com/mattermost/mattermost-server11.6.0+incompatible → 11.6.1+incompatibleosvUSpkg:golang/github.com/mattermost/mattermost-server

showing 20 of 23

advisories (2)

Vendor and ecosystem advisories describing this.

GHSA-5gmf-x7hg-97wfMattermost doesn't filter nil elements from outgoing webhook attachment payloads before processing2026-05-26ghsa · osvUS
Mattermost versions 11.6.x <= 11.6.0, 11.5.x <= 11.5.3, 11.4.x <= 11.4.4, 10.11.x <= 10.11.14 fail to filter nil elements from outgoing webhook attachment payloads before processing, which allows an authenticated user to cause a denial of service (server process termination) via a crafted webhook callback response containing a null attachment entry. Mattermost Advisory ID: MMSA-2026-00641
GO-2026-5845Mattermost doesn't filter nil elements from outgoing webhook attachment payloads before processing in github.com/mattermost/mattermost-server2026-07-07vendor · osvUS
Mattermost doesn't filter nil elements from outgoing webhook attachment payloads before processing in github.com/mattermost/mattermost-server

also known as (7)

Other names and identifiers for this entity.

sources

Which sources assert this record, and when.

cnnvd enisa_euvd fstec_bdu osv nvd NVD CVE.org MITRE

published 2026-05-25modified 2026-07-23

references (5)

External citations — patches, advisories, analysis.

scry

Attackers weaponise vulnerabilities like this against internet-exposed services. See what is exposed on your perimeter with a free passive scan.

Free scan