medium Known exploitedREV. 01
CVE-2024-39891Twilio Authy — an endpoint that confirmed phone numbers
An endpoint in the Twilio Authy service answered without a login, telling anyone who asked whether a given phone number had an account. Attackers fed it millions of numbers in June 2024. The accounts themselves were not compromised.
Read the risk
THE VITAL STATS- CVSS score
- 5.3/ 10 CVSS v3.1
- EPSS probability
- 2% Likelihood of exploitation
- Attack complexity
- Low Conditions needed to exploit
- Known exploited
- Yes — CISA KEV
- CVE published
- 2024-07-02
- Added to KEV
- 2024-07-23
- Exploit published
- Not recorded
- Confidence
- medium
- Kill chain
- reconnaissance
- MITRE ATT&CK
- T1589
- Severity
- medium
CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:L/I:N/A:N
Attacker needsNothing beyond network access to the service endpoint.
Fixed inAuthy Android >= 25.1.0, Authy iOS >= 26.1.0
Behind the card
3 REFERENCES- 01CVE recordNVD recordnvd.nist.gov
- 02CISACISA Known Exploited Vulnerabilities catalogcisa.gov
- 03Writeupcwe.mitre.orgcwe.mitre.org
Field-level provenanceTRACE THE SOURCES +
Which source supports each field, when it was retrieved, and who extracted it.
| Fields | Source | Retrieved | Extractor | Confidence |
|---|---|---|---|---|
| cvss, exploitation.attack_complexity, exploitation.exploit_available, references, published_at | nvd.nist.gov | 2026-09-24 | scrty-crds-pipeline/0.1 | high |
| exploitation.known_exploited, exploitation.kev_added | cisa.gov | 2026-09-24 | scrty-crds-pipeline/0.1 | high |
| epss | api.first.org | 2026-09-24 | scrty-crds-pipeline/0.1 | high |
| title, summary, severity, remediation, mitre_attack, kill_chain, recommended_action, confidence, tags, exploitation.prerequisites | nvd.nist.gov | 2026-09-24 | claude-code | high |
Printing history
THE RECORD- r1Initial base card
First printing. This card has not been reprinted since publication.