CVE-2026-42566 Meshtastic: Malformed UTF-8 in User.long_name broadcast over LoRa causes mesh-wide client decode failure

High 7.5 Published 19 Jul 2026 Updated 21 Jul 2026

Malformed UTF-8 in user names causes iOS app BLE sync failures, rendering devices unusable for mesh users until the bad entry expires or is manually removed.

Exploited in the wild: Not known
Login needed: Not needed
Attackable: Over the internet
Victim action needed: Not needed
Fix: None listed

What is CVE-2026-42566?

CVE-2026-42566 is a high-severity denial of service vulnerability in meshtastic firmware, published on 19 Jul 2026. An attacker can exploit it over the internet without logging in, with no action from the victim.

Official description

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.

Weakness: CWE-20

Which versions are affected by CVE-2026-42566?

It affects 1 product.

Products include Meshtastic Meshtastic Firmware.

How do I fix CVE-2026-42566?

No fix has been published for CVE-2026-42566 yet. Limit exposure of the affected software until one is available.

Upgrade, then put limits on request size, rate and nesting depth so one client cannot exhaust the service. More about Denial of service.

Is CVE-2026-42566 being exploited?

There is no known exploitation of CVE-2026-42566 in the wild and no public exploit code.

Sources

Also known as GHSA-7ph5-2mjv-69h8, UBUNTU-CVE-2026-42566.