Twilio Authy Information Disclosure
CVE-2024-39891 is a medium-severity observable discrepancy vulnerability in authy_2-factor_authentication from Twilio, with a CVSS 3.1 base score of 5.3 out of 10. It can be exploited remotely over the network by an unauthenticated attacker, without any action from a user. The record lists versions 26.1.0, 25.1.0 as the first without the flaw, so updating authy_2-factor_authentication to one of those releases or later removes the exposure. CISA added it to the Known Exploited Vulnerabilities catalogue on July 23, 2024, which means attacks have been observed in the wild.
Attackers are already exploiting this vulnerability, according to CISA.
What to do
- Update authy_2-factor_authentication to 26.1.0 or 25.1.0, whichever matches your release line, or a later version.
- Update Authy to 26.1.0 or a later version.
- Update Authy Authenticator to 25.1.0 or a later version.
- CISA's required action: Apply mitigations per vendor instructions or discontinue use of the product if mitigations are unavailable.
- Until you can update, restrict network access to the affected service so it is not reachable from untrusted networks.
Affected products and versions
| Vendor | Product | Affected versions | Fixed in |
|---|---|---|---|
| Twilio | authy_2-factor_authentication | before 26.1.0; before 25.1.0 | 26.1.0, 25.1.0 |
| Twilio | Authy | before 26.1.0 | 26.1.0 |
| Twilio | Authy Authenticator | before 25.1.0 | 25.1.0 |
Version data comes from the organisation that assigned the CVE. Confirm against the vendor advisory before deciding you are unaffected.
How the severity score breaks down
- Attack vector
- NetworkCan be exploited remotely over a network, including the internet.
- Attack complexity
- LowNo special conditions are needed; the attack works reliably.
- Privileges required
- NoneNo account or login is needed.
- User interaction
- NoneNo action by a victim is required.
- Scope
- UnchangedImpact stays within the vulnerable component.
- Confidentiality
- LowSome restricted data can be read.
- Integrity
- NoneNothing can be modified.
- Availability
- NoneAvailability is not affected.
Vector: CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:L/I:N/A:N. Scored by NVD.
| Scoring system | Score | Severity | Scored by |
|---|---|---|---|
| CVSS 3.1 | 5.3 | Medium | CNA (mitre.org) |
| CVSS 3.1 | 5.3 | Medium | NVD |
Official description
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.)
Source: the CVE record as published by its numbering authority, via NVD and CVE.org.
The underlying weakness: Observable Discrepancy
The product behaves differently or sends different responses under different circumstances in a way that is observable to an unauthorized actor.
How developers prevent this class of flaw
- Compartmentalize the system to have safe areas where trust boundaries can be unambiguously drawn. Do not allow sensitive data to go outside of the trust boundary and always be careful when interfacing with a compartment outside of the safe area. Ensure that appropriate compartmentalization is built into the system design, and the compartmentalization allows for and reinforces privilege separation functionality. Architects and designers should rely on the principle of least privilege to decide the appropriate time to use privileges and the time to drop privileges.
Timeline
- CVE record published.
- CISA published its SSVC assessment (exploitation: active, automatable: yes, technical impact: partial).
- Added to CISA's Known Exploited Vulnerabilities catalogue.
- Deadline for US federal agencies to remediate, set by CISA.
- Record last changed materially (score, affected products, status or references).
References
Patches and release notes
- twilio.com/en-us/changelogRelease Notes
Third-party and government advisories
- cisa.gov/known-exploited-vulnerabilities-catalog?field_cve=CVE-2024-39891US Government Resource
Other references
Recent Observable Discrepancy vulnerabilities
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