CVE-2026-9859

Exploitation

Assessed, none found. CISA's assessment recorded neither public exploit code nor evidence of exploitation when it was made.

SSVC decision

• ExploitationnoneCISA recorded no public exploit code and no evidence of exploitation.
• AutomatablenoAt least one step from reconnaissance to exploitation cannot be reliably automated.
• Technical ImpactpartialSuccessful exploitation gives limited control of the vulnerable component.

CISA publishes the decision points, not a final SSVC decision. The decision also depends on mission and well-being impact, which is a property of your deployment rather than of the vulnerability.

EPSS probability

0.34% probability of exploitation activity in the next 30 days.

EPSS percentile

Equal to or higher than the score of 27.2% of scored records. A rank, not a probability.

NVD base score

6.5 (CVSS v3.x), scored by the NVD independently of the CNA.

NVD CVSS vector

CVSS:3.1/AV:N/AC:L/PR:L/UI:N/S:U/C:H/I:N/A:N

NVD analysis status

Analyzed. NVD last modified this record on 2026-08-19.

Red Hat severity

No Red Hat rating. Red Hat rates the CVEs that affect its products.

Exploit-prediction scores from FIRST. Independent scoring and analysis status from the NVD. Vendor severity from Red Hat. Exploitation assessment and catalog membership from CISA.

Published

2026-08-17 22:06Z2 MO AGO

Last updated

2026-08-18 14:22Z2 MO AGO

Reserved

2026-05-28

Assigning CNA

Mattermost

Record state

PUBLISHED

Severity

Medium (CVSS 6.5)

CNA CVSS vector

CVSS:3.1/AV:N/AC:L/PR:L/UI:N/S:U/C:H/I:N/A:N

Weaknesses

• CWE-863Incorrect AuthorizationClass

Data version

5.2

Document digest

5b5a27f6805a514f6e2daf0f70670bd66b5b58ca883b8e71a3c297c227909052

• mattermost.comMMSA-2026-00686https://mattermost.com/security-updatesvendor-advisory