Security readout for executives and security teams
Plain-English summary
Twilio Authy exposed whether submitted phone numbers were registered with Authy. Attackers exploited this in June 2024 to validate phone numbers for targeting, but the sources say Authy accounts were not compromised. The main risk is privacy exposure and follow-on phishing or social-engineering against MFA users.
Executive priority
Treat this as urgent hygiene because exploitation is confirmed and MFA users are attractive targets. It is not a confirmed account-compromise event, but validated phone-number lists can materially improve attacker targeting.
Technical view
CVE-2024-39891 is an unauthenticated Authy API information-disclosure issue affecting Authy Android before 25.1.0 and iOS before 26.1.0. The endpoint revealed registration status for supplied phone numbers, matching CWE-203 observable discrepancy. CVSS is 5.3, with network access, no privileges, and low confidentiality impact.
Likely exposure
Organizations with employees, customers, or administrators using vulnerable Authy mobile versions had exposure to phone-number enumeration. Exposure is not evidence of token compromise or account takeover, but it can increase targeted smishing, phishing, and MFA-fatigue risk.
Exploitation context
The CVE record states exploitation occurred in the wild in June 2024, and CISA lists CVE-2024-39891 in KEV. BleepingComputer reported abuse to verify millions of Authy MFA phone numbers. Sources do not provide evidence that Authy accounts were compromised.
Researcher notes
Evidence supports unauthenticated enumeration of Authy registration status, not token theft. The affected surface is described as Twilio Authy API access by older Android and iOS clients. Public sources do not describe detailed server-side fixes beyond version thresholds and vendor guidance.
Mitigation direction
- Update Authy Android to 25.1.0 or later.
- Update Authy iOS to 26.1.0 or later.
- Check Twilio/Authy guidance for any additional remediation.
- Warn Authy users about targeted smishing and MFA social engineering.
- Review privileged users for phone-number exposure risk.
Validation and detection
- Inventory corporate and privileged users relying on Authy.
- Confirm deployed Authy app versions meet fixed minimums.
- Check mobile management records for outdated Authy clients.
- Monitor helpdesk and security reports for Authy-themed phishing.
- Review CISA KEV tracking for remediation deadlines.
Public sources used
Generated from the cited source records. This long-tail analysis has not been individually reviewed by a named human.
Conservative CVE-to-ATT&CK context
These mappings and lookup hints may be relevant to the vulnerability behavior, CWE, affected product, or exposure path. Glexia-inferred context is not an official MITRE, ATT&CK, CWE, or CVE Program mapping.
ATT&CK lookup starting points
Use these exact CWE pages and searches to review the Glexia ATT&CK library from this CVE's weakness and description context.
CWE-203: Information exposure and cloud metadata lookup
Information exposure and SSRF weaknesses can make discovery, cloud metadata, and credential material review relevant. Open the exact CWE lookup page first, then review the ATT&CK searches from that MITRE weakness context. This is a Glexia lookup hint, not an official ATT&CK mapping.
Open ATT&CK lookupCVE-2024-39891 mapping review
Open the CVE-to-ATT&CK bridge for reviewed, inferred, or future official mappings tied to this CVE.
Open ATT&CK lookup- Severity
- Medium
- CVSS
- 5.3 (3.1)
- Known Exploited
- Yes
- Published
Vector: CVSS:3.1/AC:L/AV:N/A:N/C:L/I:N/PR:N/S:U/UI:N
CNA and ADP enrichment extracted from CVE v5
These fields come from the CVE record and ADP containers, not from Glexia's Take. They preserve time-varying source decisions such as CISA SSVC, KEV status, CVSS metrics, and provider references.
CISA KEV status
CVSS vector scores
1 official scoreWe collect every scored CVSS vector available in the official CNA and ADP containers. When more than one version is present, the table keeps the source vectors side by side instead of collapsing them into the highest score.
CVSS:3.1/AC:L/AV:N/A:N/C:L/I:N/PR:N/S:U/UI:N3.91.4Primary CVE scoreVulnerability scoring details
Base CVSS 3.1 score
5.3MediumVector: CVSS:3.1/AC:L/AV:N/A:N/C:L/I:N/PR:N/S:U/UI:N
Source materials
- CVE List V5 sourceCVE List V5
- https://cwe.mitre.org/data/definitions/203.htmlCVE reference
- https://www.twilio.com/docs/usage/security/reporting-vulnerabilitiesCVE reference
- https://www.twilio.com/en-us/changelogCVE reference
- https://www.bleepingcomputer.com/news/security/hackers-abused-api-to-verify-millions-of-authy-mfa-phone-numbers/CVE reference
- https://www.cisa.gov/known-exploited-vulnerabilities-catalog?field_cve=CVE-2024-39891CVE reference · government-resource
Products and packages named in the record
CWE details
CWE links open Glexia weakness intelligence pages with official CWE context, developer remediation guidance, and related CVE mappings.
Observable Discrepancy
Observable Discrepancy represents a recurring weakness pattern that can create exploitable paths when design, validation, or implementation controls are missing.