CVE-2026-25793

Unknown Unknown - Not Provided

ECDSA Signature Malleability Allows Blocklist Bypass in Nebula

Publication date: 2026-02-06

Last updated on: 2026-02-18

Assigner: GitHub, Inc.

Description

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.

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Meta Information

Published

2026-02-06

Last Modified

2026-02-18

Generated

2026-07-07

AI Q&A

2026-02-07

EPSS Evaluated

2026-07-05

NVD

CVE-2026-25793

EUVD

EUVD-2026-6933

Affected Vendors & Products

Vendor	Product	Version / Range
slack	nebula	From 1.7.0 (inc) to 1.10.3 (exc)

Helpful Resources

Exploitability

CWE

KEV

CWE ID	Description
CWE-347	The product does not verify, or incorrectly verifies, the cryptographic signature for data.

Attack-Flow Graph

Executive Summary

This vulnerability affects Nebula, a scalable overlay networking tool, in versions 1.7.0 to 1.10.2 when using P256 certificates, which is not the default configuration.

The issue involves ECDSA Signature Malleability, which allows an attacker to evade a blocklist entry created against the fingerprint of a certificate by using a copy of the certificate with a different fingerprint.

This means that even if a certificate is blocked based on its fingerprint, an attacker can manipulate the signature to create a different fingerprint and bypass the blocklist.

The vulnerability was fixed in Nebula version 1.10.3.

Impact Analysis

This vulnerability can allow an attacker to bypass security controls that rely on certificate fingerprint blocklists.

As a result, unauthorized or malicious certificates could be used to gain access or communicate within the Nebula network despite being blocked.

This could lead to potential unauthorized access, data interception, or other security breaches within the network.

Compliance Impact

I don't know

Detection Guidance

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Mitigation Strategies

To mitigate this vulnerability, upgrade Nebula to version 1.10.3 or later where the issue has been patched.

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