Is CVE-2026-4858 in the CISA KEV catalog?

No. CVE-2026-4858 is not currently on the CISA Known Exploited Vulnerabilities list.

What is the CVSS severity of CVE-2026-4858?

CVE-2026-4858 has a CVSS v3 base score of 8.0 (HIGH).

What is the EPSS score for CVE-2026-4858?

CVE-2026-4858 has an EPSS score of 0.25% (16th percentile), estimating the probability of exploitation in the next 30 days.

CVE & CISA-KEV Catalog

CVE-2026-4858

HIGH

8.0

CVSS v3

NVD

Description

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 check integration URL for path traversal which allows an malicious authenticated user to call an arbitrary API via system admin Mattermost auth token using via path traversal in integration action URL.. Mattermost Advisory ID: MMSA-2026-00640

CWE-22Path Traversal

CVSS v3 Vector

Exploitability

Attack VectorNetwork

Attack ComplexityHigh

Privileges RequiredLow

User InteractionRequired

ScopeChanged

Impact

ConfidentialityHigh

IntegrityHigh

AvailabilityHigh

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

Exploit Intelligence

0.25%probability of exploitation in 30 days

16thpercentile

Low risk: more likely to be exploited than 16% of all known CVEs.

References

https://mattermost.com/security-updates

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This product uses NVD data but is not endorsed or certified by the NVD. EPSS scores courtesy of FIRST.org (https://www.first.org/epss). Source: CISA KEV Catalog. Data as of 2026-05-21.