CVE-2026-4858

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 ImpacttotalSuccessful exploitation gives total 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

0.32% probability of exploitation activity in the next 30 days.

EPSS percentile

Equal to or higher than the score of 25.6% of scored records. A rank, not a probability.

NVD base score

9.9 (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:C/C:H/I:H/A:H

NVD analysis status

Analyzed. NVD last modified this record on 2026-07-23.

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

2026-05-21 08:12Z5 MO AGO

Last updated

2026-05-22 03:55Z5 MO AGO

Reserved

2026-03-25

Assigning CNA

Mattermost

Record state

PUBLISHED

Severity

High (CVSS 8.0)

CNA CVSS vector

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

Weaknesses

• CWE-22Improper Limitation of a Pathname to a Restricted Directory ('Path Traversal')Base

Data version

5.2

Document digest

1c872339b30f39bc8e2933293aa0630097114c82b7d8ecc0cdc1c0f575e30dc9

• mattermost.comMMSA-2026-00640https://mattermost.com/security-updatesvendor-advisory