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
2026-06-16
AI Q&A
2026-02-07
EPSS Evaluated
2026-06-15
NVD
CVE-2026-25793
EUVD
EUVD-2026-6933
Affected Vendors & Products
Showing 1 associated CPE
Vendor Product Version / Range
slack nebula From 1.7.0 (inc) to 1.10.3 (exc)
Helpful Resources
Exploitability
CWE
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KEV
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CWE ID Description
CWE-347 The product does not verify, or incorrectly verifies, the cryptographic signature for data.
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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

I don't know

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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