CVE-2020-28086 in pass
Summary
by MITRE • 12/10/2020
pass through 1.7.3 has a possibility of using a password for an unintended resource. For exploitation to occur, the user must do a git pull, decrypt a password, and log into a remote service with the password. If an attacker controls the central Git server or one of the other members' machines, and also controls one of the services already in the password store, they can rename one of the password files in the Git repository to something else: pass doesn't correctly verify that the content of a file matches the filename, so a user might be tricked into decrypting the wrong password and sending that to a service that the attacker controls. NOTE: for environments in which this threat model is of concern, signing commits can be a solution.
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Analysis
by VulDB Data Team • 12/15/2020
The vulnerability identified as CVE-2020-28086 affects pass through version 1.7.3, a command-line password manager that stores passwords in git repositories. This security flaw represents a significant risk in environments where password management is centralized and automated. The vulnerability stems from a critical design weakness in how pass validates file names against their actual content within the git repository. When users execute git pull operations, pass automatically processes password files without performing proper content verification, creating an attack surface where malicious actors can manipulate the system through repository manipulation. The exploit requires a specific set of conditions to be successful, including control over the central git server or other member machines, along with access to services already present in the password store, making this a sophisticated attack vector that leverages supply chain compromise.
The technical flaw manifests in pass's failure to validate that the content of password files matches their filenames during decryption and usage processes. This validation gap creates a scenario where an attacker can rename password files within the git repository to misleading names while maintaining the actual password content. For example, an attacker could rename a password file from "server1_password" to "server2_password" while keeping the original password content, causing users to decrypt the wrong password and inadvertently provide credentials to an attacker-controlled service. This type of vulnerability aligns with CWE-200, which addresses "Information Exposure," and CWE-345, "Insufficient Verification of Data Authenticity," as it involves improper validation of file content against expected identifiers. The flaw operates at the intersection of authentication and access control mechanisms, where the system fails to properly verify the integrity and authenticity of stored credentials before deployment.
The operational impact of this vulnerability extends beyond simple credential theft, as it enables attackers to establish persistent access to systems through legitimate password management workflows. When users perform git pull operations, they unknowingly trigger the exploitation process, making this attack particularly dangerous in automated environments where regular repository synchronization occurs. The vulnerability creates a trust relationship breakdown between the password manager and the user, as the system fails to provide adequate safeguards against malicious file renaming operations. This can lead to unauthorized access to critical systems, data exfiltration, and potential lateral movement within networks where the compromised credentials are used. The attack requires specific environmental conditions to be effective, but once established, it can provide attackers with continuous access to targeted services, making it particularly concerning for organizations with centralized password management practices.
Mitigation strategies for CVE-2020-28086 should focus on implementing robust commit signing and verification mechanisms as recommended in the vulnerability description. Organizations should enable and enforce GPG commit signing within their git repositories, ensuring that all commits are cryptographically verified before being accepted into the repository. This approach aligns with ATT&CK technique T1556.004, which covers "Modify Authentication Process," by establishing cryptographic verification of repository integrity. Additional protective measures include implementing strict access controls on git repositories, regular monitoring for unauthorized file renames, and establishing automated checks that validate file content against expected naming conventions. Security teams should also consider implementing multi-factor authentication for critical systems and regularly auditing password store contents to detect unauthorized modifications. The vulnerability highlights the importance of defense in depth strategies, where cryptographic verification serves as a critical control mechanism against supply chain attacks that manipulate credential storage systems. Organizations should also review their password management workflows and consider implementing additional validation layers that verify file integrity before password usage, ensuring that the system maintains proper authentication guarantees throughout the credential access lifecycle.