CVE-2025-62820: Github.com/slackhq/nebula Remote Code Execution Vulnerability

MODERATE
Advisory Identifier: GHSA-x6fh-7qmf-69xh
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CVSS 4.9
CWE-420
Published
Advisory Summary

CVE-2025-62820 is a MODERATE (CVSS 4.9) remote code execution vulnerability (CWE-420: Unprotected Alternate Channel) affecting Github.com/slackhq/nebula libraries in the Go ecosystem. The issue involves slack nebula may accept arbitrary source ip addresses. Remediation is available by upgrading affected packages to version 1.9.7.

CVE-2025-62820 at a Glance

CVE Identifier CVE-2025-62820
GHSA Identifier GHSA-x6fh-7qmf-69xh
Severity MODERATE
CVSS v3.1 Base Score 4.9
CWE Classification CWE-420: Unprotected Alternate Channel
Affected Product Github.com/slackhq/nebula
Package Ecosystem Go
Published Date
Last Updated

Security Impact

CVSS: 4.9

The security impact metrics below are parsed directly from the CVSS v3.1 vector string (CVSS:3.1/AV:N/AC:H/PR:L/UI:N/S:C/C:N/I:L/A:L).

Attack Vector Network (AV:N)
Attack Complexity High (AC:H)
Privileges Required Low (PR:L)
User Interaction None (UI:N)
Scope Changed (S:C)
Confidentiality None (C:N)
Integrity Low (I:L)
Availability Low (A:L)

How to Fix CVE-2025-62820

To remediate this vulnerability, upgrade all affected Github.com/slackhq/nebula dependencies to a patched release. Both direct and transitive dependencies should be checked, as frameworks or security libraries may pull in vulnerable versions transitively.

github.com/slackhq/nebula fixed: 1.9.7 
Upgrade github.com/slackhq/nebula to 1.9.7
Verify Direct and Transitive Dependencies

Run the following command in your project directory to verify that all resolved dependencies use the patched release: 

inspect dependencies for github.com/slackhq/nebula

How to Check if You Are Affected

To determine whether your application is affected by CVE-2025-62820, inspect your project dependencies for Github.com/slackhq/nebula:

inspect dependencies for github.com/slackhq/nebula

Analyze the terminal output to locate any version of Github.com/slackhq/nebula in your dependency tree. If any resolved version matches the vulnerable ranges listed in the table below (for example, versions earlier than 1.9.7), your application is affected.

Note: Verify declared build manifests and deployed runtime container environments.

Technical Details

Vulnerability Mechanism & Technical Analysis

This vulnerability is classified under CWE-420: Unprotected Alternate Channel, where the product protects a primary channel, but it does not use the same level of protection for an alternate channel. In Github.com/slackhq/nebula, software state validation or input boundaries are circumvented during processing. Review the official source advisory statement below for specific affected components, classes, and reproduction details.

Source Advisory Statement

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

CVE-2025-62820 Affected Github.com/slackhq/nebula Versions

1 component(s)
Fixed Versions:
1.9.7
Product / Package Ecosystem Affected Versions Fixed Version
github.com/slackhq/nebula
golang/github.com/slackhq/nebula
Go
≥ 1.9.4
< 1.9.7
1.9.7

References

NVD — CVE-2025-62820 NVD
https://nvd.nist.gov/vuln/detail/CVE-2025-62820
Github.com/slackhq/nebula Source Repository REPOSITORY
https://github.com/slackhq/nebula/pull/1493
Github.com/slackhq/nebula Source Repository REPOSITORY
https://github.com/slackhq/nebula/pull/1494
Security Fix Commit FIX COMMIT
https://github.com/slackhq/nebula/commit/e264a0ff888c7bf0568579306755a60fc42f6ecc
Github.com/slackhq/nebula Source Repository REPOSITORY
https://github.com/slackhq/nebula

Frequently Asked Questions

What is CVE-2025-62820?
CVE-2025-62820 is a security vulnerability in Github.com/slackhq/nebula involving Slack Nebula may accept arbitrary source IP addresses under CWE-420: Unprotected Alternate Channel.
Which Github.com/slackhq/nebula versions are affected?
Affected versions include releases prior to 1.9.7 across affected packages: github.com/slackhq/nebula.
What version fixes CVE-2025-62820?
Upgrading to 1.9.7 (or the latest patched release for your respective branch) resolves the vulnerability.
Is github.com/slackhq/nebula affected?
Yes, github.com/slackhq/nebula is affected in releases prior to 1.9.7. Upgrade your dependency to 1.9.7 or later.
What is the CVSS score of CVE-2025-62820?
CVE-2025-62820 has a CVSS v3.1 base score of 4.9 (MODERATE) with vector string CVSS:3.1/AV:N/AC:H/PR:L/UI:N/S:C/C:N/I:L/A:L.
What CWE is associated with CVE-2025-62820?
CVE-2025-62820 is classified under CWE-420: Unprotected Alternate Channel (The product protects a primary channel, but it does not use the same level of protection for an alternate channel.).
How can I check Go dependencies for CVE-2025-62820?
Run the dependency tree command: 'inspect dependencies for github.com/slackhq/nebula'. This command lists direct and transitive dependencies in your build configuration so you can verify if a vulnerable version is resolved.
Machine-readable OSV JSON OSV v1.5 Schema
Normalized schema output
View Raw JSON 
{
  "schema_version" : "1.4.0",
  "id" : "GHSA-x6fh-7qmf-69xh",
  "modified" : "2025-10-23T16:49:07Z",
  "published" : "2025-10-23T06:31:00Z",
  "aliases" : [ "CVE-2025-62820" ],
  "summary" : "Slack Nebula may accept arbitrary source IP addresses ",
  "details" : "Slack Nebula before 1.9.7 mishandles CIDR in some configurations and thus accepts arbitrary source IP addresses within the Nebula network.",
  "severity" : [ {
    "type" : "CVSS_V3",
    "score" : "CVSS:3.1/AV:N/AC:H/PR:L/UI:N/S:C/C:N/I:L/A:L"
  } ],
  "affected" : [ {
    "package" : {
      "ecosystem" : "Go",
      "name" : "github.com/slackhq/nebula"
    },
    "ranges" : [ {
      "type" : "ECOSYSTEM",
      "events" : [ {
        "introduced" : "1.9.4"
      }, {
        "fixed" : "1.9.7"
      } ]
    } ]
  } ],
  "references" : [ {
    "type" : "ADVISORY",
    "url" : "https://nvd.nist.gov/vuln/detail/CVE-2025-62820"
  }, {
    "type" : "WEB",
    "url" : "https://github.com/slackhq/nebula/pull/1493"
  }, {
    "type" : "WEB",
    "url" : "https://github.com/slackhq/nebula/pull/1494"
  }, {
    "type" : "WEB",
    "url" : "https://github.com/slackhq/nebula/commit/e264a0ff888c7bf0568579306755a60fc42f6ecc"
  }, {
    "type" : "PACKAGE",
    "url" : "https://github.com/slackhq/nebula"
  } ],
  "database_specific" : {
    "cwe_ids" : [ "CWE-420" ],
    "severity" : "MODERATE",
    "github_reviewed" : true,
    "github_reviewed_at" : "2025-10-23T16:49:07Z",
    "nvd_published_at" : "2025-10-23T04:18:57Z"
  }
}