CVE-2026-9859Disclosure(mattermost / mattermost_server)

LOWCVSS 6.5 · MEDIUM

Signal is active with 2 mentions in latest observed window

Immediate actions

Track advisory updates for patch or workaround availability

Recommended action window: Monitor and triage in normal cycle

NVD description

Mattermost versions 11.7.x <= 11.7.6, 10.11.x <= 10.11.21, 11.8.x <= 11.8.3 fail to enforce PermissionManageBoardRoles on the channelId field of the batch endpoint, which allows an authenticated board editor to relink any board they can edit to an arbitrary channel via a crafted PATCH request. Mattermost Advisory ID: MMSA-2026-00686

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0.0/ 10 priority

Sources & remediation

Vendor / third-party advisories

https://mattermost.com/security-updates

Weakness type (CWE)

CWE-863

Priority

LOW

Exploitation

NONE

PoC

NONE

Patch

NONE

Momentum

NONE

Are you affected?

If you run products in this scope, you should treat this CVE as relevant to your environment.

mattermost_server

Threat summary

2 mentions across 1 observed day

What's happening

Technical details provided in 1 signal
Disclosure: 2 classified signals
2 total mentions across 1 day

Affected systems

Vendors

mattermost

Products

mattermost_server

Deep dive

Activity timeline2 mentions / 1d

Signal classification1 categories

Disclosure

2100.0%

Referenced assets2 URLs

By indicator

Full discourse2 posts

Infoflowcloud@infoflowcloud46d
Disclosure
🚨*CVE* CVE-2026-9859 Mattermost versions 11.7.x <= 11.7.6, 10.11.x <= 10.11.21, 11.8.x <= 11.8.3 fail to enforce PermissionManageBoardRoles on the channelId field of the batch endpoint, whi… https://www.cve.org/CVERecord?id=CVE-2026-9859 ----- Traducción: CVE-2026-9859 Mat… https://infoflow.cloud`
Post summary
The message announces CVE-2026‑9859 affecting multiple Mattermost releases by highlighting a permission check flaw, but lacks PoC, exploit, patch, or active exploitation details.
0000026
100 followersView on X
CVE@CVEnew46d
Disclosure
CVE-2026-9859 Mattermost versions 11.7.x <= 11.7.6, 10.11.x <= 10.11.21, 11.8.x <= 11.8.3 fail to enforce PermissionManageBoardRoles on the channelId field of the batch endpoint, whi… https://www.cve.org/CVERecord?id=CVE-2026-9859
Post summary
The post identifies affected Mattermost versions and describes a permission enforcement flaw in the batch endpoint’s channelId field, but it offers no PoC, exploit, patch, or evidence of active exploitation.
000001.5K
58.0K followersView on X

CPE platform detail1 entries

Part:

Vendor:

Product:

Version:

Target SW:

Target HW:

1 of 1 entries

Part	Vendor	Product	Version	Target SW	Target HW
App	mattermost	mattermost_server	-	-	-

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