CVE-2026-12284 — Mattermost Desktop App Missing IPC Sender Validation in Calls Leave Handler

Mattermost Desktop App versions <=6.2 6.2.2.0 fails to validate the IPC sender in the leaveCall handler which allows a malicious or compromised Mattermost server (or a user with script access to a connected server view) to disconnect an active call belonging to a different connected server via the desktopAPI.leaveCall IPC message. Mattermost Advisory ID: MMSA-2026-00699

Published Sep 17, 2026Updated Sep 17, 2026Sources: cvelistV5, Mattermost

Triage

Is it exploited, how likely is exploitation, what does it touch, and how severe do the scoring sources call it.

Exploitation

Unreported

no source claims exploitation

EPSS

chance of exploitation in 30 days

Affects

mattermost

CVSS base

3.8

LOW

CISA SSVC assessment

Three decision points CISA publishes for the CVEs it assesses · SSVC 2.0.3. A stakeholder decision, not a severity score.

CISA

Exploitation

None

none · proof-of-concept · active

Automatable

can an attacker script all four kill-chain steps

Technical impact

Partial

partial · total control of the vulnerable component

Affected scope

The catalog records vendors and products as separate lists, not pairs, so which product belongs to which vendor is not something this page can say.

Vendors (1)

mattermost

Products (1)

mattermost

Every base score collected

Sources score independently and disagree; each row says who scored it and under which version.

Score	Version	Severity	Expl.	Impact	Source
3.8	CVSS 3.1	LOW	—	—	cvelistV5

Weakness & attack patterns

CWE-346

Attack patterns reported against this CVE. The ATT&CK techniques below are inferred from its weakness class.

T1557.002Adversary-in-the-Middle: ARP Cache Poisoning
T1584.002Compromise Infrastructure: DNS Server
T1134Access Token Manipulation

References

1 on the record

mattermost.com/security-updates
vendor-advisory

Elsewhere on this site

mattermostevery CVE for this vendor
CWE-346other pages naming this weakness

Not in any source we poll

Listed rather than left blank: an empty field and an unmeasured one look identical on screen, and only one is a reason to look elsewhere.

No confirmed IOCs, IP addresses, domains, file hashes, or malware artifacts supplied.
No organization-specific asset inventory, compensating-control status, or patch deployment evidence supplied.
No exploit packet captures, log samples, or incident case IDs supplied.