Vulnerability in Slack Nebula

CVE-2025-62820

Slack Nebula before 1.9.7 mishandles CIDR in some configurations and thus accepts arbitrary source IP addresses within the Nebula network.

Published · last modified .

CVSS v3 metric

CVSS v3 base score 4.9 (Medium). Vector: CVSS:3.1/AV:N/AC:H/PR:L/UI:N/S:C/C:N/I:L/A:L.

EPSS exploit prediction

EPSS: 0.002 (11.3th percentile), scored .

Very low probability of exploitation in the next 30 days; routine patching cadence is appropriate. 11th percentile — 11.3% of CVEs in the catalogue have a lower EPSS than this one. How to read EPSS.

EPSS trend (30 days)EPSS over the last 30 days for CVE-2025-62820: held from 0.002 to 0.002.

EPSS over last 30 days · oldest: 0.002 · newest: 0.002 · change: +0.000

Affected products

Weakness classification (CWE)

References

Frequently asked questions

What is CVE-2025-62820?
CVE-2025-62820 is a medium-severity vulnerability in Slack Nebula, classified under Unprotected Alternate Channel. CVSS score: 4.9/10. Published 2025-10-23.
How severe is CVE-2025-62820?
Medium severity. CVSS v3 base score is 4.9 out of 10.