# CVE-2026-42566: Meshtastic: Malformed UTF-8 in User.long_name broadcast over LoRa causes mesh-wide client decode failure > 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. - **Severity:** High 7.5 (`CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:N/I:N/A:H`) - **Exploited in the wild:** Not known - **Login needed:** Not needed - **Attackable:** Over the internet - **Victim action needed:** Not needed - **Fix available:** No - **Published:** 19 Jul 2026 - **Updated:** 21 Jul 2026 - **Also known as:** GHSA-7ph5-2mjv-69h8, UBUNTU-CVE-2026-42566 ## 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 (Improper Input Validation) ## Which versions are affected by CVE-2026-42566? It affects 1 product. Products: 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. ## Is CVE-2026-42566 being exploited? There is no known exploitation of CVE-2026-42566 in the wild and no public exploit code. ## Other vulnerabilities in meshtastic firmware - [CVE-2025-52464](https://insights.sbomify.com/CVE-2025-52464/): Meshtastic Repeated Public and Private Keypairs (critical 9.5) - [CVE-2025-55293](https://insights.sbomify.com/CVE-2025-55293/): Meshtastic allows crafting of specific NodeInfo packets that overwrite any publicKey saved in the NodeDB (critical 9.4) - [CVE-2025-24797](https://insights.sbomify.com/CVE-2025-24797/): Meshtastic incorrectly hands malformed packets leads to controlled buffer overflow (critical 9.4) - [CVE-2025-55292](https://insights.sbomify.com/CVE-2025-55292/): In Meshtastic, an attacker can spoof licensed amateur flag for a node (high 8.2) - [CVE-2024-47078](https://insights.sbomify.com/CVE-2024-47078/): Meshtastic firmware Authentication/Authorization Bypass via MQTT (high 8.1) ## Fix prompt for AI coding agents ```text Check this codebase for CVE-2026-42566 and fix it if it is affected. What it is: 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. Exploitation: There is no known exploitation of CVE-2026-42566 in the wild and no public exploit code. Affected product: meshtastic firmware. No package-level version data is available, so check the vendor advisory linked from the reference page. Task: 1. Search the dependency manifests and lockfiles (for example package.json, package-lock.json, requirements.txt, poetry.lock, uv.lock, pom.xml, build.gradle, go.mod, Cargo.lock, Gemfile.lock) and any Dockerfiles for the affected packages, including transitive dependencies. 2. If an affected version is in use, upgrade it to the fixed version for its release line with the project's package manager, so the lockfile is regenerated. Prefer the smallest upgrade that fixes it. 3. If there is no fix, or the upgrade would break the build, do not guess: explain the risk and the safest workaround instead. 4. Run the tests and summarise what changed and why. 5. If nothing in the project is affected, say so and change nothing. Reference: https://insights.sbomify.com/CVE-2026-42566/ (Markdown: https://insights.sbomify.com/CVE-2026-42566/index.md) ``` ## Sources - CVE record: https://www.cve.org/CVERecord?id=CVE-2026-42566 - NVD: https://nvd.nist.gov/vuln/detail/CVE-2026-42566 - OSV: https://osv.dev/vulnerability/CVE-2026-42566 --- From sbomify Insights: https://insights.sbomify.com/CVE-2026-42566/ Summaries are generated and may contain mistakes; the official description above is the record.