CVE-2024-39891

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.)

CVSS: 5.3Mediumscored by the publisher (CNA)
Exploited in the wild: Yes, in CISA KEV since 23 Jul 2024CISA deadline for US federal agencies: 13 Aug 2024
EPSS: 1.7%chance of exploitation in the next 30 daystop 23% of scored CVEsFIRST score of 11 Nov 2026
Fix: Patch availablesee the advisories in the references
Published: 2 Jul 2024analysed here 12 Nov 2026

Do first. Apply mitigations per vendor instructions or discontinue use of the product if mitigations are unavailable. (CISA's required action for this KEV entry)

Summary

Triage

Exploitable: At runtime
Attack vector: network
Weakness: CWE-203 Common Weakness

The summary, impact and action text on this page are written by our AI analysis pipeline, or taken from the NVD description when a CVE was imported from NVD. They are not the vendor's wording: check them against the sources. A longer AI executive summary and technical analysis are generated for signed-in accounts on the Max plan.

Affected products

Products named in our analysis

twilio:authy
twilio:authy_authenticator

Fix and mitigation

WAF and other mitigations

Can a WAF block it? Partly. The attack involves sending HTTP requests with phone numbers to an unauthenticated API endpoint. While the requests look normal, the volume or pattern of phone numbers queried may be unusual and could be partially detected by a WAF. A custom WAF rule can filter requests containing phone numbers to an unauthenticated endpoint, but attackers can vary the request. No tracked WAF vendor has published a rule for this CVE yet.

What a custom rule would match: requests containing phone numbers to an unauthenticated endpoint

Also consider: patch · custom WAF rule

Based on an AI reading of the CVE description, and no vendor rule found yet. We check Cloudflare, AWS, Google Cloud Armor and Azure; for Akamai, Imperva, Fastly, F5, ask your vendor.

Remediation steps (AI-written)

Step-by-step remediation is generated for accounts on the Max plan, for CVEs that match a technology in their stack. Add this technology to your stack to see the fix checklist.

Exploitation evidence

CISA KEV catalog: Listed since 23 Jul 2024.
CISA due date: 13 Aug 2024, the remediation deadline for US federal agencies
CISA required action: Apply mitigations per vendor instructions or discontinue use of the product if mitigations are unavailable.
Public exploit code: None on record in Exploit-DB, Metasploit, Nuclei templates or PoC-in-GitHub.
CISA SSVC: exploitation active, automatable yes, technical impact partialAssessed by CISA 23 Jul 2024 (SSVC 2.0.3). Exploitation is none, poc (public proof of concept) or active.

Timeline

2 Jul 2024Published
23 Jul 2024Added to CISA KEV (exploited in the wild)20 days later
23 Jul 2024CISA SSVC assessment: exploitation activesame day later
13 Aug 2024CISA remediation due date (US federal agencies)21 days later
21 Oct 2025CVE record last updated435 days (about 1 year) later
12 Nov 2026Analysed by vulneraibility.com387 days (about 1 year) later

CVSS vector

CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:L/I:N/A:N

Metric	Value	What it means
Attack vector	NetworkReachable over the internet or any routable network.	Reachable over the internet or any routable network.
Attack complexity	LowRepeatable attack, no special conditions.	Repeatable attack, no special conditions.
Privileges required	NoneThe attacker needs no prior access.	The attacker needs no prior access.
User interaction	NoneNo victim action needed.	No victim action needed.
Scope	UnchangedImpact stays within the vulnerable component.	Impact stays within the vulnerable component.
Confidentiality	LowPartial data disclosure.	Partial data disclosure.
Integrity	NoneNo unauthorised modification.	No unauthorised modification.
Availability	NoneThe service stays up.	The service stays up.

Common questions

Is CVE-2024-39891 being exploited?

Yes. CVE-2024-39891 appears in CISA's Known Exploited Vulnerabilities catalog, which means exploitation in the wild has been confirmed and reported. Treat it as active rather than theoretical, and patch it ahead of higher-scoring vulnerabilities that carry no exploitation evidence.

How severe is CVE-2024-39891?

CVE-2024-39891 is rated Medium with a CVSS score of 5.3. Severity describes how bad exploitation would be, not how likely it is: pair it with exploitation evidence before deciding what to patch first.

Is there a patch for CVE-2024-39891?

Yes. A fix has been recorded for CVE-2024-39891. The vendor advisory is the authority on the exact fixed version — apply it from there rather than from a summary.

What does CVE-2024-39891 affect?

CVE-2024-39891 affects twilio:authy, twilio:authy_authenticator. Confirm the exact affected versions against the vendor advisory before deciding you are exposed.

Exploitation status reflects CISA's KEV catalog as we last synced it. Check the catalog directly.

References

NVD CVE.org CVE Details Source

5 references in the CVE record, grouped by the tags the record gives them.

Where the data on this page comes from

CVE List (CVE.org): description, affected versions, references; CVE Terms of Use
NVD: CVSS and CPE data
CISA KEV catalog: exploitation, date added, due date
CISA Vulnrichment (ADP): SSVC decision points
FIRST EPSS: exploit probability and percentile

Summary, impact and triage tags: written by our AI analysis pipeline from the sources above. Check them against the sources.

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