CVE-2026-42566 in Meshtastic
Summary
by MITRE • 07/20/2026
Meshtastic is an open source mesh networking solution. Prior to version 2.7.23.b246bcd, a single node advertising a User.long_name that contains a malformed character encoding can render other radios unusable over BLE when managed through the iOS app. The malformed name does not need to be maliciously crafted — it can arise from ordinary buffer truncation and has been observed occurring naturally in the wild. At least one code path could place a null terminator in the middle of a multibyte sequence, leaving a malformed User.long_name in the node database. The problem surfaced downstream: the iOS app enforced encoding validation and therefore cannot parse a node database once it contains a poisoned entry. This caused BLE sync to enter a fail/retry loop, resulting in loss of control over the affected device. For a typical user managing their radio with the iOS app, the device becomes effectively unusable until the poisoned node ages out of the on-device database, or unless they have an alternate management path (e.g., the Python CLI, which can be used to identify and remove the offending entries manually). Because the malformed name propagates through the mesh, the temporary presence of a single affected node can degrade BLE management for iOS users across a wide geographical area for an extended period. Less technical users have no straightforward recovery path. Starting in version 2.7.23.b246bcd, the firmware has added input sanitization and regression tests demonstrating recovery for already-poisoned devices. The apps have also taken steps to ensure more graceful handling of malformed encoding sequences as well.
If you want to get best quality of vulnerability data, you may have to visit VulDB.
Analysis
by VulDB Data Team • 07/20/2026
The Meshtastic mesh networking solution presents a critical vulnerability in versions prior to 2.7.23.b246bcd that demonstrates how seemingly benign input processing flaws can cascade into widespread operational failures within wireless mesh networks. This vulnerability specifically targets the User.long_name field which serves as a human-readable identifier for mesh nodes, creating a scenario where normal operation can inadvertently corrupt the node database through buffer truncation processes that leave malformed character sequences in memory.
The technical flaw manifests when a node advertises a User.long_name containing malformed character encoding that results from ordinary buffer truncation operations rather than malicious intent. This vulnerability stems from improper handling of multibyte character sequences where null terminators can be inserted mid-sequence, creating invalid UTF-8 or UTF-16 encoded data within the node database. The flaw operates at the intersection of CWE-129 Input Validation and CWE-704 Incorrect Calculation, as it combines buffer overflow conditions with encoding validation failures that produce corrupted data structures.
The operational impact extends far beyond individual device failure, creating a systemic degradation of mesh network management capabilities for iOS users who rely on BLE connectivity. When the iOS application attempts to synchronize with the mesh network, it encounters the malformed User.long_name entries and fails to parse the node database completely. This results in a continuous fail/retry loop that effectively renders the affected device unusable over BLE connections until either the poisoned entry ages out of the local database or manual intervention occurs through alternative management interfaces such as the Python CLI tool.
The propagation characteristics of this vulnerability amplify its impact across geographical boundaries, as mesh networks inherently share node information with neighboring devices. A single compromised node can poison the entire mesh network's node database, causing widespread disruption for iOS users within range. The cascading effect demonstrates how vulnerabilities in data handling can create network-wide degradation rather than isolated failures, affecting not just individual radios but entire geographic regions simultaneously.
The recovery mechanisms highlight the importance of defensive programming practices and input sanitization as primary mitigation strategies. Version 2.7.23.b246bcd introduced firmware-level input sanitization that prevents malformed character sequences from entering the node database in the first place, while also implementing regression testing to ensure that previously corrupted databases can be recovered. The iOS application updates address the downstream parsing issues by implementing more graceful error handling for malformed encoding sequences, following ATT&CK technique T1070.004 Indicator Removal on Host to prevent cascading failures.
This vulnerability serves as a prime example of how buffer management and character encoding validation must be carefully considered in embedded systems within mesh networks, where the failure of one device can affect network-wide operations. The issue demonstrates the necessity of robust input validation at multiple layers of the system architecture, from firmware level through application interfaces, and highlights the importance of graceful degradation mechanisms that prevent single points of failure from causing complete system outages.
The remediation approach taken by Meshtastic developers aligns with security best practices by implementing both preventive measures through input sanitization and corrective measures through improved error handling. This dual approach addresses the root cause while also providing resilience against similar vulnerabilities in the future, demonstrating proper vulnerability management that follows industry standards for secure software development lifecycle practices.