Authy API: Unauth Endpoint Exposes Phone # Data (Android <25.1.0 / iOS <26.1.0)
CVE-2024-39891 Published on July 2, 2024
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.)
Known Exploited Vulnerability
This Twilio Authy Information Disclosure Vulnerability is part of CISA's list of Known Exploited Vulnerabilities. Twilio Authy contains an information disclosure vulnerability in its API that allows an unauthenticated endpoint to accept a request containing a phone number and respond with information about whether the phone number was registered with Authy.
The following remediation steps are recommended / required by August 13, 2024: Apply mitigations per vendor instructions or discontinue use of the product if mitigations are unavailable.
Vulnerability Analysis
CVE-2024-39891 can be exploited with network access, and does not require authorization privileges or user interaction. This vulnerability is considered to have a low attack complexity. This vulnerability is known to be actively exploited by threat actors in an automatable fashion. The potential impact of an exploit of this vulnerability is considered to have a small impact on confidentiality, a small impact on integrity and availability.
Weakness Type
What is a Side Channel Attack Vulnerability?
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. Discrepancies can take many forms, and variations may be detectable in timing, control flow, communications such as replies or requests, or general behavior. These discrepancies can reveal information about the product's operation or internal state to an unauthorized actor. In some cases, discrepancies can be used by attackers to form a side channel.
CVE-2024-39891 has been classified to as a Side Channel Attack vulnerability or weakness.
Products Associated with CVE-2024-39891
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Exploit Probability
EPSS (Exploit Prediction Scoring System) scores estimate the probability that a vulnerability will be exploited in the wild within the next 30 days. The percentile shows you how this score compares to all other vulnerabilities.