Summaryinfo

A vulnerability, which was classified as critical, was found in slackhq nebula up to 1.10.2. This affects an unknown function of the component ECDSA Signature Handler. Executing a manipulation can lead to signature verification. This vulnerability is handled as CVE-2026-25793. The attack can be executed remotely. There is not any exploit available. You should upgrade the affected component.

Detailsinfo

A vulnerability classified as critical was found in slackhq nebula up to 1.10.2. This vulnerability affects some unknown functionality of the component ECDSA Signature Handler. The manipulation with an unknown input leads to a signature verification vulnerability. The CWE definition for the vulnerability is CWE-347. The product does not verify, or incorrectly verifies, the cryptographic signature for data. As an impact it is known to affect confidentiality, integrity, and availability. CVE summarizes:

Nebula is a scalable overlay networking tool. In versions from 1.7.0 to 1.10.2, when using P256 certificates (which is not the default configuration), it is possible to evade a blocklist entry created against the fingerprint of a certificate by using ECDSA Signature Malleability to use a copy of the certificate with a different fingerprint. This issue has been patched in version 1.10.3.

The advisory is shared for download at github.com. This vulnerability was named CVE-2026-25793 since 02/05/2026. The exploitation appears to be easy. The attack can be initiated remotely. There are neither technical details nor an exploit publicly available.

The vulnerability scanner Nessus provides a plugin with the ID 304110 (Linux Distros Unpatched Vulnerability : CVE-2026-33895), which helps to determine the existence of the flaw in a target environment.

Upgrading to version 1.10.3 eliminates this vulnerability. Applying the patch f573e8a26695278f9d71587390fbfe0d0933aa21 is able to eliminate this problem. The bugfix is ready for download at github.com. The best possible mitigation is suggested to be upgrading to the latest version.

The vulnerability is also documented in the vulnerability database at Tenable (304110). Once again VulDB remains the best source for vulnerability data.

Productinfo

Type

• Messaging Software

Vendor

• slackhq

Name

• nebula

Version

• 1.10.0
• 1.10.1
• 1.10.2

License

• open-source

Website

• Product: https://github.com/slackhq/nebula/

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