SB20260425201 - Improper Verification of Cryptographic Signature in Nebula

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Main Vulnerability Database SB20260425201

SB20260425201 - Improper Verification of Cryptographic Signature in Nebula

Published: April 25, 2026

Security Bulletin ID SB20260425201
Severity
Medium
Patch available
YES
Number of vulnerabilities 1
Exploitation vector Remote access
Highest impact Data manipulation

Breakdown by Severity

Medium 100%
  • Low
  • Medium
  • High
  • Critical

Description

This security bulletin contains information about 1 security vulnerability.


1) Improper Verification of Cryptographic Signature (CVE-ID: CVE-2026-25793)

The vulnerability allows a remote user to bypass certificate blocklist enforcement.

The vulnerability exists due to improper handling of ECDSA signature malleability in certificate fingerprint blocklist validation when processing P256 certificates. A remote user can use a copy of a certificate with a different fingerprint to bypass certificate blocklist enforcement.

Exploitation requires the use of CURVE_P256 certificates, an existing blocklist entry for a certificate signed by a trusted CA that is not expired, and access to the corresponding private key and certificate.


Remediation

Install update from vendor's website.

References