CVE-2026-49258: Auth Bypass (CVSS 8.8)

Description

Nebula Mesh is a self-hosted control plane for the Slack Nebula mesh VPN. In versions 0.3.5 and below, the web UI (/ui/*) does not apply the per-operator CA scoping employed by the JSON API. This was partially addressed by GHSA-598g-h2vc-h5vg, but the changes were not implemented in the web read/mutation surface. Any authenticated non-admin operator (for example, one created via self-registration or OIDC) can access resources belonging to other operators. The host create/edit/mobile-bundle/network-create paths and all CA-management routes were already correctly scoped. A malicious operator could block or delete any other operator's host, or read any operator's hosts and networks. This issue has been fixed in version 0.3.6.

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CVSS v3.1 Score

8.8

HIGH

CVSS:3.1/AV:N/AC:L/PR:L/UI:N/S:U/C:H/I:H/A:H

EPSS — Exploit Prediction

0.0028

Probability of exploitation

0.20%

Percentile rank

EPSS estimates the probability that this vulnerability will be exploited in the wild within the next 30 days. A higher score means more likely to be exploited.

Weakness Type (CWE)

CWE-639 CWE-639

CWE-862 Missing Authorization

References

Other References

https://github.com/forgekeep/nebula-mesh/pull/161 https://github.com/forgekeep/nebula-mesh/security/advisories/GHSA-c6v2-3ffm-vcmc

Frequently Asked Questions

What is CVE-2026-49258? +

Nebula Mesh is a self-hosted control plane for the Slack Nebula mesh VPN. In versions 0.3.5 and below, the web UI (/ui/*) does not apply the per-operator CA scoping employed by the JSON API. This was partially addressed by GHSA-598g-h2vc-h5vg, but the changes were not implemented in the web read/mutation surface. Any authenticated non-admin operator (for example, one created via self-registration or OIDC) can access resources belonging to other operators. The host create/edit/mobile-bundle/network-create paths and all CA-management routes were already correctly scoped. A malicious operator could block or delete any other operator's host, or read any operator's hosts and networks. This issue has been fixed in version 0.3.6. It has a CVSS v3.1 base score of 8.8 (HIGH).

How severe is CVE-2026-49258? +

CVE-2026-49258 has a CVSS v3.1 score of 8.8 out of 10, rated HIGH. This is a high-severity vulnerability that should be prioritized for patching. The EPSS score is 0.0028, placing it in the 0th percentile for exploitation probability.

How do I check if I'm vulnerable to CVE-2026-49258? +

You can use Secably's free Website Scanner to check your website for known vulnerabilities. For infrastructure scanning, use the Port Scanner to identify exposed services that may be affected. Check the vendor advisories linked above for specific patch and version information.

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