CVE-2024-39891
CVE-2024-39891 is a security flaw in Twilio Authy. Attackers can read information from Twilio Authy that should be private from anywhere, without logging in. The US Cybersecurity and Infrastructure Security Agency (CISA) added it to its catalog of flaws known to be used in attacks on 23 Jul 2024.[1]
Twilio Authy is business software or equipment. Most families won’t have it, but attackers break into it to get inside companies, and from there to what those companies hold about their customers, patients and staff. Fixed in version 26.1.0 and 25.1.0 of authy_2-factor_authentication.
Description
CISA calls it an information disclosure in Twilio Authy. In its words: “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.”[1]
The CVE record adds: “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.)”[2]
The underlying weakness is CWE-203, in MITRE’s list of common software weaknesses.
It scores 5.3 out of 10 on the Common Vulnerability Scoring System, which rates it medium, scored by NVD using CVSS 3.1.[2]
Affected versions
NVD’s record lists these fixed versions: in each line, everything before the version shown is affected.[2]
| Product | Fixed in |
|---|---|
| authy_2-factor_authentication | 26.1.0 |
| authy_2-factor_authentication | 25.1.0 |
Most families won’t have Twilio Authy; it’s for whoever looks after IT at work.
Exploitation
CISA added it to its catalog of known exploited vulnerabilities on 23 Jul 2024, 21 days after it was made public. CISA lists a flaw only when it has reliable evidence of it being exploited, and gave US federal agencies until 13 Aug 2024 to fix it.[1]
FIRST’s Exploit Prediction Scoring System, which estimates how likely a flaw is to be used in attacks in the next 30 days from what it sees across the internet, puts it at 2%. That’s in the top 24% of the flaws it scores.[4]
CISA assesses it as automatable: attackers can run it against many targets at once.
CISA doesn’t say who was attacked, or how.
Fix
Twilio has published a fix or advice.[3] CISA’s required action: “Apply mitigations per vendor instructions or discontinue use of the product if mitigations are unavailable.”[1]
- Check whether you use it.Twilio Authy is business software or equipment, so most families won’t have it. If you run a business, or work from home on company equipment, ask whoever looks after your IT.
- Send this page to your IT person.Ask them to confirm it’s fixed (fixed in version 26.1.0 and 25.1.0 of authy_2-factor_authentication), or not in use. CISA gave US government agencies until 13 Aug 2024 to fix it.
- If it can’t be fixed, take it offline.CISA’s advice when there’s no fix is to stop using the product, or take it off the internet, until there is one.
You can’t fix someone else’s server, but you can watch for what follows a break-in like this: a breach notice, a password reset you didn’t ask for, or a scam message that knows things it shouldn’t. HARD watches for those for you and your family.
Timeline
| Date | Event |
|---|---|
| The flaw is made public in the National Vulnerability Database, with a severity score of 5.3.[2] | |
| CISA adds it to its catalog of flaws known to be used in attacks.[1] | |
| CISA’s deadline for US government agencies to fix it.[1] | |
| FIRST puts the odds of it being used in attacks in the next 30 days at 2%.[4] |
See also
Added the same day
- CVE-2012-4792, Microsoft Internet Explorer: use-after-free ·
References
- ^ Cybersecurity and Infrastructure Security Agency. “Twilio Authy Information Disclosure Vulnerability”. Known Exploited Vulnerabilities Catalog, added 23 Jul 2024.
- ^ National Institute of Standards and Technology. “CVE-2024-39891 Detail”. National Vulnerability Database, published 2 Jul 2024.
- ^ Twilio. Advisories and fixes: twilio.com, twilio.com.
- ^ FIRST. “Exploit Prediction Scoring System”. EPSS 0.017, percentile 76.8, 31 Oct 2026.
- CVE Program. “CVE-2024-39891”. The official CVE record.
This article is built from CISA’s catalog (version 2026.10.30), NVD’s record and FIRST’s scores, kept in HARD’s database and checked every morning. The plain English is HARD’s.