⚠ Reference material — not professional advice. Test in staging, back up first, verify against your specific version. Use your own judgment for your environment.
● High · CVSS 7.1

How to Fix CVE-2026-3861: Denial of service in LINE client for iOS

By Sai Kiran Pandrala. Last verified: 2026-05-25.

⚡ At a glance
Severity7.1 (High)
Actively exploited?No public listing in CISA KEV
AffectedLY Corporation LINE client for iOS
Fixed inSee vendor advisory
Type (CWE)CWE-400: denial of service

What is CVE-2026-3861?

LINE client for iOS versions prior to 26.3.0 contains a vulnerability in the in-app browser where opening a crafted web page can repeatedly trigger OS-level dialogs due to insufficient safeguards when handling arbitrary URL schemes, potentially causing the iOS device to become temporarily inoperable.

Am I affected?

Run the version check that matches your platform:


# macOS
sw_vers
brew list --versions line 2>/dev/null

Compare what you see against the Affected row above (LY Corporation LINE client for iOS). If your build sits inside that range, you are exposed and should patch.

How to fix CVE-2026-3861

The primary fix is to upgrade LINE client for iOS to the patched build. Use the commands for your platform below; the patched version listed in the vendor advisory is: See vendor advisory.

macOS


# System updates (Apple-issued patches)
softwareupdate --list
sudo softwareupdate --install --all --restart

# For third-party tools managed by Homebrew
brew update
brew upgrade

Complete macOS / iOS remediation script


#!/usr/bin/env bash
# CVE-2026-3861 fix script for LINE client for iOS
# Run on each affected Mac. iOS / iPadOS / watchOS / tvOS devices update via Settings.

set -euo pipefail
LOG="$HOME/Library/Logs/cve-2026-3861-fix-$(date +%Y%m%d-%H%M%S).log"
exec > >(tee -a "$LOG") 2>&1

echo "[1/4] Current OS version"
sw_vers

echo "[2/4] Listing available Apple updates"
softwareupdate --list || true

echo "[3/4] Installing all pending Apple security updates"
sudo softwareupdate --install --all --restart

echo "[4/4] Verifying"
sw_vers
echo "For iPhone / iPad: Settings -> General -> Software Update."
echo "For Apple Watch:   Watch app -> General -> Software Update."
echo "For Apple TV:      Settings -> System -> Software Updates -> Update Software."

If you can't patch immediately

If you cannot apply the patched version today, restrict exposure with one of the following runnable controls. None replace the patch.

Service-level fallback


# If the affected feature is optional, stop the service until the patch is applied
sudo systemctl stop line
sudo systemctl disable line

How to verify the fix worked


# Linux
line --version 2>/dev/null || dpkg -s line | grep -i version
rpm -q line 2>/dev/null || true


# Windows
winget list | findstr /I "line"
Get-HotFix | Sort-Object InstalledOn -Descending | Select-Object -First 5

Expected: the reported version is at or above the patched build documented in the advisory. Restart any services that loaded the old library (systemctl restart <service> on Linux, restart the Windows service or reboot when prompted). For network appliances, run show version on the device and confirm the build matches the patched release.

Frequently asked questions

Other vulnerabilities in the same area that are worth patching alongside this one:

Is CVE-2026-3861 actually being exploited?

According to the data sources above, no public confirmation of in-the-wild exploitation at this time. Either way, the fix is the same: apply the vendor patch.

Do I need to reboot after patching?

For OS or kernel updates, yes. For most userland packages a systemctl restart <service> is enough. Any process that loaded the old shared library keeps using it until restarted, so when in doubt, reboot.

What is the CVSS score?

7.1 (high). Refer to the vendor advisory for the exact vector string.

Where is the official advisory?

See the References section at the bottom of this page; the vendor's URL is the authoritative source for affected builds and patched versions.

References

*Written by Sai Kiran Pandrala. Assembled from the official vendor advisory, NVD record, and CISA KEV listing on 2026-05-25. Always confirm against the vendor's advisory before applying changes in production.*