Slack Nebula before 1.9.7 mishandles CIDR in some configurations and thus accepts…
Priority LOW 22CWE-420Published · Updated
Key facts
- Attack vector
- Network
- Privileges required
- Low
- User interaction
- None
- Attack complexity
- High
- Impact type
- —
- Confidentiality · integrity · availability
- None · Low · Low
- Fix status
- Fixed
Attack profile from CVSS 3.1 · CNA. Fix status from CNA and GitHub.
Summary
Slack Nebula before 1.9.7 mishandles CIDR in some configurations and thus accepts arbitrary source IP addresses within the Nebula network.
Why it matters now
Exploitation None reported CISA SSVC · not in CISA KEV
EPSS 0.0022 12th percentileScored 2026-11-07
Fix Fixed Nebula (Slack): 1.9.7github.com/slackhq/nebula (Go): 1.9.7
SSVC decision points
CISA ADP · SSVC 2.0.3
- Exploitation
- None
- Automatable
- No
- Technical impact
- Partial
The decision (Track, Attend, Act) also depends on your mission and well-being impact; see CISA's SSVC guide.
Affected products
| Vendor | Product | Affected versions | Fixed in | Status | Source |
|---|---|---|---|---|---|
| Slack | Nebula | before 1.9.7 | 1.9.7 | Patch available | CNA |
| — | github.com/slackhq/nebula (Go) | 1.9.4 to before 1.9.7 | 1.9.7 | Patch available | GHSA-x6fh-7qmf-69xh |
- Nebula VendorSlack Affected before 1.9.7 Fixed in 1.9.7 Patch available CNA
- github.com/slackhq/nebula (Go) Vendor— Affected 1.9.4 to before 1.9.7 Fixed in 1.9.7 Patch available GHSA-x6fh-7qmf-69xh
Remediation
- Fix · CNA Nebula (Slack) Fixed in 1.9.7
- Fix · GHSA-x6fh-7qmf-69xh github.com/slackhq/nebula (Go) Fixed in 1.9.7 Advisory →
Vendor assessments
Timeline
- 2026-10-02 Threatist record created from CVE-2025-62820
- 2026-10-03 Alias added: GHSA-x6fh-7qmf-69xh
References
More Slack vulnerabilities
- TI-2020-09222 Slack Nebula through 1.1.0 contains a relative path vulnerability that allows a… CVSS 3.1HIGH 8.8
- TI-2019-10709 WP SlackSync plugin through 1.8.5 for WordPress leaks a Slack Access Token in source code. CVSS 3.1HIGH 7.5
- TI-2026-20857 Nebula Has Possible Blocklist Bypass via ECDSA Signature Malleability CVSS 4.0HIGH 7.6
Sources
- CVE-2025-62820 · CVE Program
- CVE-2025-62820 · NVD
- FIRST EPSS
- GHSA-x6fh-7qmf-69xh · GitHub Advisory Database · CC BY 4.0
- CVE-2025-62820 · Red Hat security data · CC BY 4.0
This product uses the NVD API but is not endorsed or certified by the NVD. Sources and licences