CVE-2022-29173 is a vulnerability in go-tuf, a Go language implementation of The Update Framework (TUF), which is designed to secure software update systems by ensuring the integrity and freshness of update metadata. The vulnerability arises from improper validation of integrity check values, specifically in the client workflow for updating metadata files related to roles other than the root role. The core issue is that go-tuf does not correctly implement rollback attack protections. Rollback attacks occur when an attacker causes a client to accept and install older versions of software, potentially reintroducing known vulnerabilities or malicious code that had been patched in later versions. Technically, the vulnerability manifests in two main ways: First, the client does not consider previously trusted metadata when updating non-root roles, leading to version verification checks being performed against a default zero value, which always passes. This flaw violates the intended TUF client workflow steps 5.4.3.1 and 5.5.5, which require comparing new metadata versions against previously trusted versions to prevent rollback. Second, for timestamp and snapshot roles, the client prematurely saves newly downloaded metadata as trusted before verifying the correctness of the version numbers they reference (contravening steps 5.5.4 and 5.6.4). This premature trust can allow attackers to present stale metadata that appears valid, enabling rollback. The vulnerability affects all go-tuf versions prior to 0.3.0, with a fix implemented in version 0.3.0 and later. No known workarounds exist aside from upgrading to a patched version. While no exploits have been observed in the wild, the flaw undermines a fundamental security guarantee of TUF, potentially allowing attackers to distribute outdated and vulnerable software updates to clients relying on go-tuf for secure update delivery.

For European organizations, the impact of this vulnerability can be significant, particularly for those relying on go-tuf as part of their software supply chain security. The improper validation of metadata integrity and versioning can lead to rollback attacks, enabling adversaries to force the installation of outdated software versions with known vulnerabilities. This can compromise confidentiality, integrity, and availability of systems by reintroducing exploitable flaws, potentially facilitating further compromise such as privilege escalation, data breaches, or service disruptions. Industries with critical infrastructure, such as finance, healthcare, telecommunications, and manufacturing, which often depend on secure update mechanisms, may face increased risk. The vulnerability could be exploited to undermine trust in software updates, leading to operational disruptions or regulatory compliance issues under frameworks like GDPR or NIS Directive. Additionally, organizations using go-tuf in automated deployment pipelines or IoT device management could see widespread impact if rollback attacks are successful. Given that no authentication or user interaction is required for the update process, and the scope includes all clients using vulnerable go-tuf versions, the attack surface is broad. Although no active exploitation is reported, the potential for supply chain compromise and cascading effects on software integrity makes this a medium to high concern for European entities dependent on this framework.

The primary and only effective mitigation is to upgrade all go-tuf implementations to version 0.3.0 or later, where the rollback protection logic has been correctly implemented. Organizations should audit their software supply chains and update infrastructure to ensure no legacy versions of go-tuf remain in use. Beyond upgrading, organizations should implement the following practical measures: 1. Conduct a comprehensive inventory of all software components and update frameworks in use, verifying whether go-tuf is employed directly or indirectly. 2. Integrate strict version and metadata validation checks in the update pipeline to detect and block any attempts to install older software versions. 3. Employ additional monitoring and anomaly detection on update metadata and software versions to identify unexpected downgrades or suspicious update patterns. 4. Use cryptographic signing and verification of all update metadata and payloads, ensuring signatures are validated against trusted keys. 5. For critical systems, implement multi-factor verification of updates or out-of-band validation mechanisms to reduce reliance on a single update framework. 6. Engage with software vendors and open-source communities to track updates and patches related to go-tuf and TUF implementations. These steps, combined with timely patching, will significantly reduce the risk posed by this vulnerability.