# CVE-2026-3861: LINE client for iOS denial of service in in-app browser

Source: https://junglewise.ai/threats/cve-2026-3861-line-client-for-ios-denial-of-service-in-in-app-browser  
Publisher: Junglewise Threat Intelligence, https://junglewise.ai/threats  
Published: 2026-04-16. Updated: 2026-07-08  
License: CC BY 4.0 with a link back

CVE-2026-3861 · Severity: medium · CVSS 6.5 · Published 2026-04-16

The LINE messaging app for iOS contains a flaw in its built-in web browser. If a user visits a malicious website through the app, the site can force the phone to display a continuous loop of system alerts. This can effectively freeze the device and make it unusable until the app is closed or the phone is restarted.

Technologies: [Linecorp Line](https://junglewise.ai/threats/technologies/line). Vendors: [Linecorp](https://junglewise.ai/threats/vendors/linecorp).

## Quick answers

**Is CVE-2026-3861 exploited in the wild?** No. Junglewise Threat Intelligence has no report of CVE-2026-3861 being exploited in the wild.

**How severe is CVE-2026-3861?** Medium severity, with a CVSS score of 6.5, published 16 April 2026.

**Which products and versions are affected?** LY Corporation LINE client for iOS versions prior to 26.3.0.

**Is there a fix for CVE-2026-3861?** No fixed version is recorded yet. Check the vendor's advisory in the references below. If you run it, Junglewise drafts a mitigation that fits your setup and applies it once you approve, with senior security engineers behind it.

**How is CVE-2026-3861 attacked?** It is attacked over the network, in a network appliance.

**Am I affected by CVE-2026-3861?** Check whether you run Linecorp Line. Junglewise does that check for you around the clock: connect your code, cloud and domains, and it matches new vulnerabilities like this one against what you actually run and tells you when one reaches you.

## Technical details

A vulnerability exists in the in-app browser of the LINE iOS application due to insufficient safeguards when handling arbitrary URL schemes. By enticing a user to visit a specially crafted webpage, a remote attacker can trigger a loop of OS-level dialogs (CWE-451). This results in a denial-of-service condition where the device becomes temporarily inoperable due to the persistent UI interference. The issue is resolved in version 26.3.0.

## Affected products

- LY Corporation LINE client for iOS versions prior to 26.3.0

## Timeline

- 2026-04-16: disclosed
- 2026-04-16: advisory

## References

- [https://hackerone.com/reports/3422905](https://hackerone.com/reports/3422905)

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