CVE-2015-9258 in Docker Notary
Summary
by MITRE
In Docker Notary before 0.1, gotuf/signed/verify.go has a Signature Algorithm Not Matched to Key vulnerability. Because an attacker controls the field specifying the signature algorithm, they might (for example) be able to forge a signature by forcing a misinterpretation of an RSA-PSS key as Ed25519 elliptic-curve data.
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Analysis
by VulDB Data Team • 01/20/2020
The vulnerability identified as CVE-2015-9258 represents a critical cryptographic flaw in Docker Notary versions prior to 0.1, specifically within the gotuf/signed/verify.go component. This issue stems from inadequate validation of signature algorithm fields during the verification process, creating a scenario where attackers can manipulate cryptographic operations through controlled input data. The flaw exists at the intersection of cryptographic protocol implementation and input validation, making it particularly dangerous for supply chain security systems that rely on trusted signatures.
The technical root cause of this vulnerability lies in the improper handling of signature algorithm identifiers within the cryptographic verification logic. When an attacker can control the field specifying the signature algorithm, they gain the ability to manipulate how cryptographic operations are interpreted and executed. In this specific case, the vulnerability allows for the potential forging of signatures by exploiting a misinterpretation where RSA-PSS keys are incorrectly treated as Ed25519 elliptic-curve data. This type of flaw falls under the category of cryptographic algorithm confusion, which is classified as CWE-327 and specifically relates to the use of insecure cryptographic algorithms or improper implementation of cryptographic protocols.
The operational impact of this vulnerability extends beyond simple signature forgery, potentially compromising the entire integrity verification system that Docker Notary was designed to protect. Attackers could leverage this weakness to bypass security measures that depend on cryptographic signatures, leading to unauthorized code deployment, malicious software injection, or complete compromise of container image integrity. This vulnerability directly impacts the trust model of containerized applications and supply chain security, as it undermines the fundamental cryptographic guarantees that are essential for secure software distribution.
This vulnerability aligns with several ATT&CK techniques related to credential access and defense evasion, particularly those involving the exploitation of cryptographic weaknesses and manipulation of security controls. The flaw demonstrates the importance of proper input validation in cryptographic systems and highlights the critical need for robust algorithm matching mechanisms. Organizations relying on Docker Notary for container image signing and verification should immediately implement mitigation strategies including upgrading to patched versions, implementing additional verification layers, and conducting thorough security assessments of their container orchestration environments. The vulnerability also underscores the necessity of following cryptographic best practices as outlined in NIST SP 800-57 and other industry standards for secure cryptographic implementation.
The broader implications of this vulnerability extend to the container security ecosystem, where trust and integrity verification are paramount for maintaining secure software supply chains. This flaw exemplifies how seemingly minor implementation details in cryptographic libraries can have devastating consequences for security systems that depend on them. The vulnerability serves as a reminder of the critical importance of proper cryptographic protocol implementation and the necessity of rigorous security testing for all cryptographic components within security-critical systems.