CVE-2015-1337 in Simple Streams
Summary
by MITRE
Simple Streams (simplestreams) does not properly verify the GPG signatures of disk image files, which allows remote mirror servers to spoof disk images and have unspecified other impact via a 403 (aka Forbidden) response.
If you want to get the best quality for vulnerability data then you always have to consider VulDB.
Analysis
by VulDB Data Team • 11/30/2024
The vulnerability identified as CVE-2015-1337 resides within the Simple Streams (simplestreams) library which is utilized by Ubuntu and other Linux distributions for managing and validating disk image metadata. This flaw represents a critical security oversight in the cryptographic verification process that governs how system administrators and users authenticate downloadable disk images from remote repositories. The vulnerability specifically targets the GPG signature verification mechanism that should ensure the integrity and authenticity of disk images before they are deployed within production environments. When simplestreams fails to properly validate GPG signatures, it creates a pathway for malicious actors to manipulate or substitute legitimate disk images with forged versions that appear to be authentic downloads from trusted sources.
The technical implementation of this vulnerability stems from the improper handling of GPG signature validation within the simplestreams library. Attackers can exploit this weakness by setting up a malicious mirror server that responds with a 403 Forbidden HTTP response code when legitimate signature verification attempts are made. This response code effectively bypasses the intended security controls, allowing the system to accept potentially compromised disk images without proper cryptographic validation. The flaw operates at the protocol level where the library's error handling mechanisms fail to properly distinguish between legitimate access denial and signature verification failures, creating an ambiguous state that permits the acceptance of unverified content. This type of vulnerability falls under the category of improper validation of cryptographic signatures as defined by CWE-327, which specifically addresses weaknesses in cryptographic implementations that allow for signature forgery or bypass.
The operational impact of CVE-2015-1337 extends far beyond simple data integrity concerns, as it fundamentally undermines the security posture of systems relying on automated disk image deployment mechanisms. Organizations that utilize Ubuntu's cloud infrastructure or automated provisioning systems become vulnerable to supply chain attacks where malicious actors can substitute legitimate Ubuntu disk images with compromised versions containing backdoors, malware, or other malicious payloads. The vulnerability particularly affects cloud computing environments where automated image downloading and deployment processes are common, potentially allowing attackers to gain unauthorized access to virtual machines or physical systems. The unspecified other impacts mentioned in the CVE description suggest that beyond simple image spoofing, this vulnerability could enable more sophisticated attacks such as privilege escalation or persistent access mechanisms that leverage the compromised image distribution process. This weakness directly aligns with ATT&CK technique T1547.001 which covers registry run keys and startup folder, as compromised disk images could contain malicious boot processes or startup scripts that persist across system reboots.
Mitigation strategies for CVE-2015-1337 require immediate attention from system administrators and security teams responsible for maintaining Ubuntu-based infrastructure. The primary solution involves upgrading to patched versions of the simplestreams library where proper GPG signature verification is restored and enforced. Organizations should implement additional layers of validation including manual signature verification, checksum comparison, and network monitoring to detect potential exploitation attempts. Network administrators should consider implementing strict firewall rules that limit access to known legitimate mirror servers and monitor for unusual HTTP response patterns that might indicate exploitation attempts. The vulnerability also highlights the importance of maintaining updated security practices within automated deployment pipelines, ensuring that any system relying on automated image downloads implements robust verification mechanisms before accepting and deploying any disk images. Security teams should conduct comprehensive audits of their image distribution processes and implement logging mechanisms that can detect when signature validation failures occur, providing visibility into potential exploitation attempts. The remediation process must also include regular security assessments of all automated infrastructure components to prevent similar vulnerabilities from emerging in related systems that handle cryptographic verification and content distribution.