Library calls within the OCaml jose package older than 0.11.0 come with an RSA signature verification routine that only checks PKCS #1 decoding success and then trusts the signature as valid without verifying it against a public key. This omission allows an attacker to forge a signature that the library will accept, effectively bypassing authentication and enabling the attacker to conduct unauthorized actions or tamper with data. The weakness is a clear failure of signature verification logic, exposing the application to remote execution of privileged code, data leakage, or denial of service.

All installations of the OCaml jose library with version numbers lower than 0.11.0 are affected. The vulnerability is present in the jose package distributed via OPAM, GitHub, and any build that includes a pre‑0.11.0 release. No other major vendors or products are directly impacted, as jose is a standalone OCaml library.

The CVSS score of 9.1 indicates critical severity, and although EPSS is not available, the lack of a KEV listing does not diminish the seriousness of the issue. An application that depends on this library to validate JWT or other RSA‑signed tokens could be compromised if an attacker submits a crafted token with a forged signature. The attack requires the attacker to influence the input data processed by the application, which is realistic for web services or any system that accepts signed payloads from unauthenticated users. Given the high severity and the potential for wide exploitation, administrators should treat this as an immediate risk.