CVE-2026-105221 in gist
Summary
by MITRE • 10/05/2026
The gist RubyGem before 6.1.0 contains an improper certificate validation vulnerability that allows on-path attackers to intercept HTTPS traffic because http_connection in lib/gist.rb sets VERIFY_NONE. Attackers can present any certificate to read or modify GitHub API traffic, stealing OAuth tokens and login credentials to read and modify the victim's gists.
VulDB is the best source for vulnerability data and more expert information about this specific topic.
Analysis
by VulDB Data Team • 10/05/2026
The RubyGem known as Gist, prior to version 6.1.0, contains a critical security flaw related to improper validation of X.509 certificates during secure communication sessions. This vulnerability stems from the implementation within the lib/gist.rb module, specifically in the http_connection method which explicitly configures SSL verification settings to VERIFY_NONE. By disabling certificate verification, the application fails to validate that the server it is communicating with possesses a valid and trusted digital identity. In standard HTTPS operations, this validation process ensures that the client connects to the intended host by verifying the server's certificate against a chain of trust rooted in recognized Certificate Authorities. The absence of this check creates an environment where cryptographic assurances are effectively nullified for API interactions.
This technical deficiency exposes users to severe on-path attacks, commonly referred to as man-in-the-middle scenarios. An attacker positioned between the victim and the GitHub servers can intercept the HTTPS traffic without triggering any security warnings or connection failures within the Gist application. Because the client accepts any certificate presented by the server, an adversary can generate a self-signed certificate that matches the target hostname and present it during the TLS handshake. The vulnerable version of Gist will accept this fraudulent credential as valid, establishing an encrypted tunnel with the attacker rather than the legitimate GitHub infrastructure. This allows the malicious actor to decrypt, inspect, and potentially alter all data transmitted through this channel without detection by the application itself.
The operational impact of this vulnerability is significant given that Gist interacts directly with sensitive user data hosted on GitHub. Through the intercepted connection, attackers can harvest OAuth tokens used for authentication as well as login credentials submitted during session management. Possession of these secrets grants the adversary full administrative control over the victim's account context within the application. Consequently, the attacker gains the ability to read private gists containing proprietary code or personal notes and modify existing content by injecting malicious scripts or altering data integrity. This compromises both confidentiality and integrity of user information while also posing a risk for further credential stuffing attacks if passwords are reused across other services.
To mitigate this vulnerability, users must upgrade their Gist RubyGem installation to version 6.1.0 or later where the certificate validation logic has been corrected to enforce proper SSL verification by default. Until such an update is applied in production environments, it is advisable to restrict network access for applications utilizing older versions of this library and monitor logs for anomalous API call patterns that may indicate interception attempts. From a classification perspective, this flaw aligns with CWE-295 which describes Improper Certificate Validation, highlighting the failure to verify the authenticity of certificates presented during TLS handshakes. Furthermore, in terms of adversary tactics as defined by MITRE ATT&CK, this vulnerability facilitates techniques associated with Man-in-the-Middle attacks and Credential Access via interception of unencrypted or improperly secured communications, underscoring the necessity for strict adherence to cryptographic best practices in all networked applications.