---
id: CVE-2025-62820
title: >-
  Slack Nebula before 1.9.7 mishandles CIDR in some configurations and thus
  accepts arbitrary source IP addresses within the Nebula network.
summary: >-
  Slack Nebula before 1.9.7 mishandles CIDR in some configurations and thus
  accepts arbitrary source IP addresses within the Nebula network.
severity: medium
cvss: 4.9
cvssVector: 'CVSS:3.1/AV:N/AC:H/PR:L/UI:N/S:C/C:N/I:L/A:L'
cwe:
  - CWE-420
published: '2025-10-23'
updated: '2026-10-08'
sourceUpdated: '2026-10-08T11:10:00.250'
source: NVD
sourceUrl: 'https://nvd.nist.gov/vuln/detail/CVE-2025-62820'
references:
  - url: 'https://github.com/slackhq/nebula/pull/1493'
    label: cve@mitre.org
  - url: 'https://github.com/slackhq/nebula/pull/1494'
    label: cve@mitre.org
tags:
  - nvd
epss: 0.0022
epssPercentile: 0.11476
ingestedAt: '2026-10-08T11:31:27.555Z'
---

## Overview

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

## Remediation

Refer to the linked advisories for vendor-supplied fixes and affected version ranges.