CVE-2026-70579: Windows Mobile Broadband Info Disclosure

CVE-2026-70579 Overview

CVE-2026-70579 is an out-of-bounds read vulnerability [CWE-125] in the Windows Mobile Broadband component. An unauthenticated attacker can exploit the flaw over a network to read memory contents outside allocated buffer boundaries. Successful exploitation results in information disclosure from the affected system.

The vulnerability requires no privileges and no user interaction to exploit. Microsoft published the advisory on September 8, 2026, and rates the issue as high severity based on the confidentiality impact. No public proof-of-concept code or in-the-wild exploitation has been reported at the time of publication.

Critical Impact
Unauthenticated network attackers can read out-of-bounds memory in the Windows Mobile Broadband stack, potentially exposing sensitive kernel or process memory contents.

Affected Products

Windows Mobile Broadband component
Microsoft Windows (versions listed in the Microsoft Security Update CVE-2026-70579)
Systems with active mobile broadband (WWAN) interfaces

Discovery Timeline

2026-09-08 - CVE CVE-2026-70579 published to NVD
2026-09-08 - Last updated in NVD database

Technical Details for CVE-2026-70579

Vulnerability Analysis

The flaw resides in the Windows Mobile Broadband subsystem, which manages cellular WWAN connections. The component processes protocol messages received over the network interface and fails to validate buffer boundaries during a read operation. An attacker sending crafted traffic can cause the code to read memory beyond the intended buffer.

The confidentiality impact is high while integrity and availability remain unaffected. This pattern is consistent with information disclosure primitives that leak process memory, pointer values, or cryptographic material. Attackers commonly chain such leaks with memory corruption bugs to bypass address space layout randomization (ASLR) and achieve reliable code execution.

The EPSS score is 1.049% at the 62nd percentile, indicating moderate probability of exploitation activity over the next 30 days.

Root Cause

The root cause is an out-of-bounds read [CWE-125] in a parsing or message-handling routine within the Mobile Broadband stack. The affected code path processes attacker-controllable length or offset fields without verifying they remain within the bounds of the source buffer.

Attack Vector

Exploitation occurs over a network. An attacker with access to send crafted Mobile Broadband protocol traffic to a vulnerable interface can trigger the out-of-bounds read. No authentication, privileges, or user interaction are required. Because the attack surface depends on active WWAN interfaces, exposure is highest on laptops, tablets, and IoT devices with cellular modems.

No verified public exploit code is available. See the Microsoft Security Update CVE-2026-70579 advisory for authoritative technical details on the vulnerable code path and impacted builds.

Detection Methods for CVE-2026-70579

Indicators of Compromise

Unexpected inbound traffic targeting Mobile Broadband service ports on WWAN-enabled endpoints
Anomalous crashes or watchdog resets in wwansvc.dll or related Mobile Broadband service processes
Repeated malformed WWAN protocol frames observed at the cellular network edge

Detection Strategies

Monitor endpoint telemetry for abnormal behavior in the Windows Mobile Broadband service and related driver stack
Correlate crash dumps and Windows Error Reporting events referencing the Mobile Broadband components
Alert on unusual network activity patterns targeting devices with active WWAN adapters

Monitoring Recommendations

Enable verbose logging for the Mobile Broadband service on high-value endpoints with cellular connectivity
Ingest Windows Event Log and crash telemetry into a centralized SIEM for correlation
Track patch compliance across all WWAN-capable devices in the fleet

How to Mitigate CVE-2026-70579

Immediate Actions Required

Apply the Microsoft security update referenced in the Microsoft Security Update CVE-2026-70579 advisory
Inventory all endpoints with active Mobile Broadband (WWAN) hardware and prioritize patching
Restrict exposure of WWAN interfaces on systems that do not require cellular connectivity

Patch Information

Microsoft has released a security update addressing CVE-2026-70579. Consult the Microsoft Security Update CVE-2026-70579 advisory for the specific KB articles, affected builds, and update packages applicable to your Windows version.

Workarounds

Disable the Mobile Broadband service (wwansvc) on systems that do not use cellular connectivity
Remove or disable WWAN hardware adapters via Device Manager where operationally acceptable
Apply network segmentation to limit adversary access to WWAN-enabled devices until patches are deployed

bash

# Disable the Windows Mobile Broadband service where cellular connectivity is not required
sc.exe config wwansvc start= disabled
sc.exe stop wwansvc