VulnerabilityPublished 2 Jul 2024Updated 21 Oct 2025

CVE-2024-39891: Twilio Authy · Observable Discrepancy

Affects Twilio AuthySource CVE Database V5

Exploited in the wild · KEV due 13 Aug 2024 · 1% EPSS : upgrade to 26.1.0 or 25.1.0 now.

Data as of 26 Oct 2026, 13:47 UTC

CVSS 3.1 base score

5.3Medium

How severe the flaw is on the 0–10 CVSS scale.

KEV deadline: 13 Aug 2024 US federal agencies must patch by this date; a sensible deadline for everyone else. Other KEV due dates
EPSS: 1.6% chance of exploitation in 30 days – higher than 76% of CVEsExploit Prediction Scoring System: the likelihood attackers will use this flaw soon.
Patch: Available – fixed in 26.1.0, 25.1.0

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

Attack Complexity: Low
Attack Vector: Network
Availability: None
Confidentiality: Low
Integrity: None
Privileges Required: None
Scope: Unchanged
User Interaction: None

Bold values are the worst case: easiest to exploit or largest impact.

Attack Complexity: Low: Specialized access conditions or extenuating circumstances do not exist. An attacker can expect repeatable success against the vulnerable component.
Attack Vector: Network: The vulnerable component is bound to the network stack and the set of possible attackers extends beyond the other options listed, up to and including the entire Internet. Such a vulnerability is often termed 'remotely exploitable' and can be thought of as an attack being exploitable at the protocol level one or more network hops away (e.g., across one or more routers).
Availability: None: There is no impact to availability within the impacted component.
Confidentiality: Low: There is some loss of confidentiality. Access to some restricted information is obtained, but the attacker does not have control over what information is obtained, or the amount or kind of loss is limited. The information disclosure does not cause a direct, serious loss to the impacted component.
Integrity: None: There is no loss of integrity within the impacted component.
Privileges Required: None: The attacker is unauthorized prior to attack, and therefore does not require any access to settings or files to carry out an attack.
Scope: Unchanged: An exploited vulnerability can only affect resources managed by the same security authority. In this case, the vulnerable component and the impacted component are either the same, or both are managed by the same security authority.
User Interaction: None: The vulnerable system can be exploited without any interaction from any user.

Definitions: FIRST CVSS v3.1 specification.

Exploitation evidence

t = 0 is the CVE’s publication on cve.org

Disclosed: evidence found.
CVE published 2 Jul 2024
Detectable: no evidence on record.
No public nuclei template indexed
Weaponised: no evidence on record.
No public exploit code indexed in Metasploit or Exploit-DB
Exploited in the wildExploited: evidence found.
Listed in CISA KEV 21 days after disclosure
Observed by OffSeq MirageSeen by Mirage: no evidence on record.
No attack traffic recorded by OffSeq Mirage sensors

CVE published
on cve.org
2 Jul 2024, t = 0
Added to CISA KEV (opens in a new tab)
exploitation confirmed
23 Jul 2024, 21 days after disclosure
KEV remediation due
US federal deadline
13 Aug 2024, 42 days after disclosure

A missing step is not evidence of safety. Sources: cve.org (opens in a new tab), CISA KEV (opens in a new tab), the Metasploit, Exploit-DB and nuclei-templates index as of 26 Oct 2026.

Disclosed: The CVE record is public on cve.org. Its publication is t = 0.
Detectable: A public nuclei template can find exposed instances, for defenders and attackers alike.
Weaponised: Public exploit code exists in Metasploit or Exploit-DB, or CISA SSVC or the CVSS exploit maturity reports a public proof of concept.
Exploited in the wild: CISA KEV lists it, CISA SSVC rates exploitation active, or a source reports attacks.
Observed by OffSeq Mirage: OffSeq Mirage honeypot sensors recorded attack traffic for this CVE, or found exposed hosts without attack traffic.

Moments are spaced evenly, not to scale; a dashed line marks a gap of six months or more. Deltas count from t = 0. Sources that give only a date (CISA KEV, Exploit-DB, or a time of exactly 00:00Z) read “same day” rather than hours. Metasploit modules carry the flaw’s disclosure date, not their release date, and nuclei templates carry no date, so both appear above but not on the timeline.

What to do

Upgrade Twilio Authy to 26.1.0 or 25.1.0.

Affected software

Product	Affected	Fixed in
Twilio Authy	Affected <25.1.0 <26.1.0	Fixed in 25.1.0 26.1.0

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.)

Impact

The primary impact of CVE-2024-39891 is the unauthorized disclosure of whether specific phone numbers are registered with the Authy two-factor authentication service. This leakage of user registration data compromises confidentiality but does not directly affect the integrity or availability of Authy accounts or services. However, the exposed information can facilitate targeted social engineering, phishing campaigns, or reconnaissance by attackers seeking to identify users who rely on Authy for authentication. Organizations using Authy for securing sensitive accounts may face increased risk of targeted attacks against their employees or customers. The vulnerability's ease of exploitation—requiring no authentication or user interaction—amplifies its threat potential. While no direct account compromise has been reported, the information disclosure could be a stepping stone for more sophisticated attacks. The impact is especially significant for organizations with high-value targets or those in sectors where phone-based authentication is prevalent.

Mitigation

To mitigate CVE-2024-39891, organizations and users should promptly update Authy Android clients to version 25.1.0 or later and Authy iOS clients to version 26.1.0 or later, where the vulnerability has been addressed. Network-level controls such as rate limiting and anomaly detection on API endpoints can help detect and block suspicious enumeration attempts. Organizations should monitor logs for unusual patterns of phone number queries against Authy services. Employing additional layers of authentication beyond phone number verification can reduce the risk posed by this information disclosure. Security teams should educate users about phishing and social engineering risks that may arise from leaked registration data. Finally, Twilio should be engaged to confirm patch availability and ensure secure API endpoint configurations to prevent unauthenticated access.

CWE-203Observable Discrepancy (opens in a new tab)
Base weakness
The product behaves differently or sends different responses under different circumstances in a way that is observable to an unauthorized actor.
Architecture and Design · Separation of Privilege
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.
Implementation
Ensure that error messages only contain minimal details that are useful to the intended audience and no one else. The messages need to strike the balance between being too cryptic (which can confuse users) or being too detailed (which may reveal more than intended).
OWASP Cheat Sheets
Error Handling (opens in a new tab)
Logging (opens in a new tab)
OWASP ASVS 4.0.3
V8.3.4 (opens in a new tab)
V14.3.3 (opens in a new tab)
V7.3.3 (opens in a new tab)
Attack patterns
Black Box Reverse Engineering (opens in a new tab)
From MITRE CWE, MITRE CAPEC and OWASP (Top 10, OpenCRE).

References

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Exploitation evidence

Timeline

What to do

Affected software

Description

AI analysisMachine-generated, updated 28 Feb 2026, 04:37 UTC

WeaknessesCWE-203

Technical details

References

Community reviews

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