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

Severity: critical (CVSS 9.3 v4.0)
Exploited in the wild: not listed in CISA KEV
EPSS: 0.6% probability of exploitation in the next 30 days
Public exploit or detection template: none known
Published: 2026-05-27 · updated 2026-10-26
Weakness: CWE-288

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.

Affected products

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

How to fix

Upgrade to a fixed version: Slican CCT-1668 6.56.0430; Slican CXS-0424 6.30.0510; Slican IPL-256 6.61.0040; Slican IPM-032 6.61.0040; Slican MAC-6400 6.56.0430. Check the vendor advisory for mitigations.

References

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

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