Phison PS3111‑S11 controller firmware verifies RSA signatures by storing the public modulus inside the firmware image. Attackers can create a new RSA key pair, sign altered firmware with the private key, embed the new modulus in the signature segment, and the controller accepts the tampered image. This permits the loading of arbitrary firmware, effectively enabling attackers to execute any code on the device. The weakness corresponds to CWE‑347, improper validation of cryptographic signatures.

The only affected product listed is Phison Electronics Corporation’s PS3111‑S11 controller firmware. No specific firmware versions are enumerated beyond the model, but any device implementing this firmware is potentially vulnerable until corrected.

The vulnerability carries a CVSS score of 9.3, indicating critical severity. EPSS is not available, but the high CVSS suggests a substantial likelihood of exploitation especially in supply chain or manufacturing scenarios. It is not yet recorded in CISA KEV. The exploit requires the attacker to supply or modify the firmware image and sign it with a key that the controller will trust. This means that devices which accept externally signed firmware without immutable key storage can be compromised when an adversary gains access to firmware distribution or manufacturing. The risk for end‑users is that a compromised controller could execute arbitrary code, potentially compromising data integrity and confidentiality.