CVE-2026-55306: Cellular Modem DOS Vulnerability

CVE-2026-55306 Overview

CVE-2026-55306 is a denial of service vulnerability in a cellular modem component disclosed through the Android Security Bulletin. The flaw stems from improper input validation classified as [CWE-20]. A remote attacker can trigger the condition over the network without authentication and without user interaction. Successful exploitation causes loss of availability on affected devices, disrupting cellular connectivity. The issue does not grant additional execution privileges and does not compromise confidentiality or integrity.

Critical Impact
Remote attackers can disrupt cellular modem availability without authentication or user interaction, resulting in denial of service on affected mobile devices.

Affected Products

Android devices incorporating the affected cellular modem component
Google Pixel devices listed in the September 2026 Android Security Bulletin
Downstream OEM builds derived from the impacted modem firmware baseline

Discovery Timeline

2026-09-15 - CVE-2026-55306 published to the National Vulnerability Database
2026-09-16 - Last updated in NVD database

Technical Details for CVE-2026-55306

Vulnerability Analysis

The vulnerability resides in the cellular modem's input handling path. The component fails to properly validate attacker-supplied input received over the cellular network interface. Malformed or unexpected data can drive the modem into an error state that halts service. Because the modem processes radio-layer traffic before higher-level application logic executes, the flaw is reachable without any user interaction.

The advisory categorizes the issue under [CWE-20] Improper Input Validation. The result is a high-impact availability loss confined to the affected device or devices within the attacker's radio range. Confidentiality and integrity remain intact, and the attacker gains no code execution or privilege elevation.

Root Cause

The root cause is insufficient validation of fields within data structures processed by the cellular modem. When the modem parses a message containing values outside expected boundaries, the parsing routine reaches an unhandled state. This condition leads to a fault that terminates modem operation and interrupts cellular service.

Attack Vector

The attack vector is network-based and requires no privileges or user interaction. An attacker with the ability to transmit crafted radio-layer messages to the target modem can trigger the fault. This typically requires proximity and equipment capable of interacting with cellular protocols, such as a rogue base station. See the Android Security Bulletin September 2026 for vendor technical detail.

No verified proof-of-concept code is available. Refer to the
Android Security Bulletin for vendor-supplied technical detail.

Detection Methods for CVE-2026-55306

Indicators of Compromise

Unexpected cellular radio resets, modem crashes, or repeated modem service restarts recorded in device logs.
Sudden loss of cellular connectivity across multiple devices in the same geographic area without carrier-side outages.
Anomalous baseband log entries referencing malformed protocol messages or parser faults.

Detection Strategies

Monitor mobile device management (MDM) telemetry for spikes in modem reboot events or connectivity loss reports.
Correlate radio access network (RAN) telemetry with device-side failure reports to identify potential rogue base station activity.
Track Android system logs and vendor modem crash dumps for repeated failures tied to specific protocol handlers.

Monitoring Recommendations

Enroll fleet devices in MDM platforms that report patch level and surface abnormal reboot patterns.
Establish a baseline for modem availability metrics so that deviations can be flagged quickly.
Review carrier and enterprise mobility reports for clustered connectivity failures that may indicate targeted exploitation.

How to Mitigate CVE-2026-55306

Immediate Actions Required

Apply the September 2026 Android security patch level to all affected devices as soon as the OEM release is available.
Inventory devices using the affected cellular modem component and prioritize patch deployment for high-risk users.
Verify that automatic OTA updates are enabled and functioning across the managed device fleet.

Patch Information

Google addressed the vulnerability in the September 2026 Android Security Bulletin. Device manufacturers integrate the fix into their own security patch releases on a rolling schedule. Confirm the patch level on each device matches or exceeds the 2026-09-01 security patch level published in the Android Security Bulletin September 2026.

Workarounds

Restrict use of cellular connectivity in untrusted radio environments where rogue base station activity is plausible.
Prefer Wi-Fi networks with device airplane mode enabled for cellular where operational needs allow, until patches are deployed.
Enforce MDM policies that accelerate patch adoption and block use of devices below the September 2026 patch level for sensitive roles.

bash

# Verify Android security patch level on a connected device
adb shell getprop ro.build.version.security_patch
# Expected output should be 2026-09-01 or later