CVE-2026-56975: Cellular Modem DOS Vulnerability

CVE-2026-56975 Overview

CVE-2026-56975 is an improper input validation flaw [CWE-20] in a cellular modem component. An attacker within radio proximity can trigger a denial-of-service condition on the affected device. Exploitation requires no authentication, no user interaction, and no additional execution privileges. The vulnerability is tracked in the Android Security Bulletin September 2026.

Critical Impact
A proximal attacker can cause loss of cellular connectivity or full device unavailability by sending malformed radio input to the modem, disrupting communications until the device recovers.

Affected Products

Devices incorporating the vulnerable cellular modem firmware referenced in the September 2026 Android Security Bulletin
Pixel devices covered by the September 2026 Pixel Security Bulletin
Downstream OEM builds that ship the affected modem component

Discovery Timeline

2026-09-15 - CVE-2026-56975 published to the National Vulnerability Database (NVD)
2026-09-16 - Record last modified in NVD

Technical Details for CVE-2026-56975

Vulnerability Analysis

The flaw resides in the cellular modem's input validation logic. The modem processes over-the-air signaling without adequately validating attacker-controlled fields. Malformed input drives the modem into an error state that terminates or restarts modem services, producing a denial of service.

Because the modem sits below the application processor, disruption affects voice, SMS, and mobile data simultaneously. The condition can persist until the modem subsystem resets or the device reboots. No confidentiality or integrity impact is documented; the failure is limited to availability.

Root Cause

The root cause is improper input validation [CWE-20] within a modem message-handling routine. The component accepts protocol data from adjacent radio sources and fails to enforce bounds or structural constraints before parsing. Malformed values reach code paths that cannot handle them safely, causing a crash or unrecoverable state.

Attack Vector

The attack requires adjacent network access, meaning the attacker must be within radio range of the target. This is typically achieved with a rogue base station or software-defined radio operating on the same cellular bands as the victim. The attacker transmits crafted signaling frames toward the target modem. No pairing, authentication, or user interaction is required.

No public proof-of-concept, exploit code, or in-the-wild exploitation has been reported. The vulnerability is not listed in the CISA Known Exploited Vulnerabilities catalog. Refer to the Android Security Bulletin September 2026 for vendor technical details.

Detection Methods for CVE-2026-56975

Indicators of Compromise

Repeated, unexplained modem resets or radio interface layer (RIL) restarts on managed mobile devices
Sudden loss of cellular registration across multiple devices in the same physical area
logcat or vendor modem logs containing crash traces from the cellular baseband subsystem

Detection Strategies

Correlate mobile device management (MDM) telemetry for spikes in modem crash events or connectivity loss on affected device models
Monitor for the presence of unauthorized cellular transmitters in sensitive facilities using RF surveys or IMSI-catcher detection tools
Track patch level compliance to identify devices still exposed to the September 2026 bulletin fixes

Monitoring Recommendations

Ingest mobile device crash and connectivity telemetry into a centralized analytics platform for anomaly detection
Alert on clusters of modem failures that coincide in time and location, which may indicate active radio-based exploitation
Review vendor security bulletins monthly and map published CVEs against your device fleet inventory

How to Mitigate CVE-2026-56975

Immediate Actions Required

Apply the September 2026 Android security patch level to all affected devices as soon as vendor builds are available
Inventory devices that cannot receive the September 2026 patch and prioritize replacement or restricted deployment
Restrict use of high-value mobile devices in untrusted RF environments until patched

Patch Information

The fix is delivered through the September 2026 Android Security Bulletin. Device manufacturers integrate the modem vendor patch into their monthly security updates. Confirm the device reports the 2026-09-01 (or later) security patch level under system settings. See the Android Security Bulletin September 2026 for the authoritative advisory and affected component list.

Workarounds

Enable airplane mode or disable cellular radios when operating in areas where rogue base stations are a credible threat
Prefer Wi-Fi calling and enterprise Wi-Fi for critical communications on unpatched devices
Enforce MDM policies that report and quarantine devices below the required security patch level

bash

# Verify Android security patch level via ADB
adb shell getprop ro.build.version.security_patch
# Expected output: 2026-09-01 or later