CVE-2026-21061 Overview
CVE-2026-21061 is an improper input validation vulnerability [CWE-20] in the Samsung Dialer application. Versions prior to Samsung Mobile Release (SMR) Aug-2026 Release 1 fail to properly validate input, allowing remote attackers to access SIM-related functions. Exploitation requires user interaction, which raises the attack complexity but does not eliminate the risk on unpatched Samsung devices. Samsung addressed the flaw in the August 2026 security maintenance release.
Critical Impact
Remote attackers can reach SIM-related functionality on affected Samsung devices when a user is convinced to interact with malicious content, potentially exposing telephony-layer operations and confidential data tied to the SIM.
Affected Products
- Samsung Dialer application on Samsung mobile devices
- Samsung devices running firmware prior to SMR Aug-2026 Release 1
- Samsung Android builds that have not applied the August 2026 security maintenance release
Discovery Timeline
- 2026-08-10 - CVE-2026-21061 published to the National Vulnerability Database (NVD)
- 2026-08-10 - Last updated in NVD database
Technical Details for CVE-2026-21061
Vulnerability Analysis
The flaw resides in the Samsung Dialer application, which handles telephony user interface actions including dialing, call management, and interactions with SIM-related functions. The Dialer accepts input from external sources without sufficient validation. A remote attacker can craft input that reaches SIM-related handlers exposed by the Dialer.
Because the Dialer runs with the privileges required to interact with telephony and SIM services, reaching these functions from an unprivileged remote context breaks the application's intended trust boundary. The Common Weakness Enumeration classification is [CWE-20] Improper Input Validation. Exploitation is remote and requires user interaction, such as opening a link or a message that triggers the Dialer with attacker-controlled parameters.
Root Cause
The Samsung Dialer does not adequately validate the content, structure, or origin of input passed to code paths that reach SIM-related operations. Missing validation permits values that the Dialer's SIM handlers were not designed to receive from untrusted sources. Samsung's August 2026 advisory tracks the fix as part of SMR Aug-2026 Release 1.
Attack Vector
The attack vector is network-based with user interaction required. An attacker delivers crafted content, such as a tel: URI, an SMS, or a web link, that causes the Dialer to process attacker-controlled input. When the victim taps or otherwise interacts with the payload, the Dialer routes the input to SIM-related functionality without validating it, granting the attacker access to functions that should require local or privileged context.
No verified public exploit code is available for this issue. Refer to the Samsung Security Update August 2026 for advisory details.
Detection Methods for CVE-2026-21061
Indicators of Compromise
- Unexpected Dialer activity such as unsolicited launches, SIM prompts, or dialogs triggered by an inbound message or link
- Outbound telephony events (calls, USSD codes, SIM toolkit actions) that do not correlate with user activity
- Delivery of SMS or web content containing crafted tel: URIs or Dialer deep links from untrusted senders
Detection Strategies
- Inventory Samsung devices in mobile device management (MDM) and flag builds older than SMR Aug-2026 Release 1
- Inspect mobile telemetry for Dialer intents originating from browsers, messaging apps, or unknown sources
- Correlate Dialer launches with preceding SMS, MMS, or URL clicks to identify user-interaction-driven exploitation attempts
Monitoring Recommendations
- Forward mobile threat defense and MDM logs to a centralized analytics platform for anomaly review
- Track carrier-side call detail records for anomalous short codes, USSD strings, or premium-rate numbers
- Alert on SIM state changes, PIN prompts, or SIM toolkit actions that occur outside normal user workflows
How to Mitigate CVE-2026-21061
Immediate Actions Required
- Apply the August 2026 Samsung security maintenance release (SMR Aug-2026 Release 1) to all affected devices
- Enforce patch compliance through MDM policies and quarantine devices that cannot receive the update
- Instruct users to avoid tapping telephony links or SIM prompts from unsolicited messages until patched
Patch Information
Samsung released the fix in SMR Aug-2026 Release 1 as part of its August 2026 monthly security update. Update details are available in the Samsung Security Update August 2026 advisory. Device availability depends on model and carrier distribution schedules.
Workarounds
- Disable or restrict handling of tel: URIs from untrusted apps and browsers where policy allows
- Block SMS and messaging content from unknown senders using carrier and MDM filtering
- Educate users to reject unexpected Dialer prompts and to verify SIM-related actions initiated by messages or links
# Verify Samsung security patch level on a connected device via ADB
adb shell getprop ro.build.version.security_patch
# Expected: a date of 2026-08-01 or later, corresponding to SMR Aug-2026 Release 1
Disclaimer: This content was generated using AI. While we strive for accuracy, please verify critical information with official sources.
