In the Twilio Authy API, accessed by Authy Android before 25.1.0 and Authy iOS before 26.1.0, an unauthenticated endpoint provided access to certain phone-number data, as exploited in the wild in June 2024. Specifically, the endpoint accepted a stream of requests containing phone numbers, and responded with information about whether each phone number was registered with Authy. (Authy accounts were not compromised, however.)
The product behaves differently or sends different responses under different circumstances in a way that is observable to an unauthorized actor, which exposes security-relevant information about the state of the product, such as whether a particular operation was successful or not.
| Link | Tags |
|---|---|
| https://cwe.mitre.org/data/definitions/203.html | technical description |
| https://www.twilio.com/docs/usage/security/reporting-vulnerabilities | product |
| https://www.twilio.com/en-us/changelog | release notes |
| https://www.bleepingcomputer.com/news/security/hackers-abused-api-to-verify-millions-of-authy-mfa-phone-numbers/ | press/media coverage |