CWE-288Weakness · CWE-288

CVE-2026-35090

CRITICAL · 9.3 CVSS v4.0 Published 2026-05-27

Mitigation only

No fix yet — a mitigation exists. There is no fixed release. A documented workaround reduces exposure in the meantime.

See remediation →

100/100

Remediation priority · Urgent

Remotely reachable No privileges Zero-click

Official description

NVD · unedited

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.

Technical summary

dbcve analysis · high confidence

This is an authentication bypass vulnerability in Slican telephone exchange systems. An unauthenticated attacker can call the modem with a specific caller ID to bypass admin authentication and gain full access to the configuration panel. If remote access is disabled, the caller ID triggers a temporary enablement. This affects multiple models including IPL-256, IPM-032, CCT-1668, MAC-6400, and CXS-0424.

MitigationApply vendor-supplied firmware updates to patched versions (IPL-256/IPM-032: 6.61.0040, CCT-1668/MAC-6400: 6.56.0430, CXS-0424: 6.30.0510). End-of-life devices (CCT-1668, MAC-6400, CXS-0424 in v4.xx) require hardware replacement as software updates cannot be applied.

Verify against the referenced sources before acting — the references below are authoritative for this CVE, this summary is not.

CVSS breakdown

From the vector

Attack vector: Network
Complexity: Low
Privileges: None
Authentication: X
User interaction: None
Scope: X

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/E:X/CR:X/IR:X/AR:X/MAV:X/MAC:X/MAT:X/MPR:X/MUI:X/MVC:X/MVI:X/MVA:X/MSC:X/MSI:X/MSA:X/S:X/AU:X/R:X/V:X/RE:X/U:X

Am I affected?

dbcve checks

Work through these to decide whether this CVE applies to you.

Identify the Slican device model

Locate the device label on the hardware unit, or access the admin web interface and check the System Information or Status page for the model number (IPL-256, IPM-032, CCT-1668, MAC-6400, or CXS-0424)

Affected if The device model is one of IPL-256, IPM-032, CCT-1668, MAC-6400, or CXS-0424
Determine the installed firmware version

In the admin web interface, navigate to Settings, System, or About section and record the firmware version number displayed (format typically xx.xx.xxxx)

Affected if The firmware version is lower than 6.61.0040 for IPL-256/IPM-032, lower than 6.56.0430 for CCT-1668/MAC-6400, or lower than 6.30.0510 for CXS-0424
Verify if remote access is enabled

In the admin web interface, locate the Remote Access, Remote Management, or Network Access settings and check whether remote HTTP/HTTPS management is currently allowed

Affected if Remote access is enabled (the caller ID can also temporarily enable it if disabled)
Check if the device is exposed to caller ID/callback access

Review network firewall rules and telephony line connections to determine if the device modem or callback interface is reachable from untrusted networks or external phone lines

Affected if The device modem or callback interface is accessible from untrusted networks or external phone lines

A defender is affected if they run any of the listed Slican models with firmware below the patched versions and the device or its modem is reachable from untrusted callers or networks.

Generated from the published advisory. Verify against your own configuration.

Remediation

dbcve · scoped

Mitigation available No clean upgrade yet — mitigate in the meantime

Mitigation

Apply vendor-supplied firmware updates to patched versions (IPL-256/IPM-032: 6.61.0040, CCT-1668/MAC-6400: 6.56.0430, CXS-0424: 6.30.0510). End-of-life devices (CCT-1668, MAC-6400, CXS-0424 in v4.xx) require hardware replacement as software updates cannot be applied.

Recommended fix High confidence

Upgrade to fixed version: IPL-256 and IPM-032 to 6.61.0040; CCT-1668 and MAC-6400 to 6.56.0430; CXS-0424 to 6.30.0510

1. Identify the Slican telephone exchange model (IPL-256, IPM-032, CCT-1668, MAC-6400, or CXS-0424) currently in use
2. Check the current firmware/software version installed on the device
3. For non-EOL products: Download and install the fixed firmware version from Slican's official support channels
4. For CCT-1668, MAC-6400, or CXS-0424 running versions 4.xx (EOL products): Contact Slican's service department to arrange hardware upgrade required for software updates
5. After upgrade, verify that the caller ID-based authentication bypass no longer functions
6. Confirm remote access controls remain in the intended state regardless of incoming caller ID

Caveat EOL products (CCT-1668, MAC-6400, CXS-0424 in 4.xx) require hardware replacement/update before software can be patched; contact vendor for upgrade options

Generated from the published advisory — verify against the referenced sources before acting.

Have this fixed Scoped from the published advisory

Consultation4.0 h
Implementation8.0 h
Testing4.0 h
Review / QA2.0 h

18.0 hours of engineering $3,200

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References

Primary sources

cert.pl
nvd.nist.govNVD record

Practitioner notes

Contributed

Peer-ranked notes from engineers who’ve handled CVE-2026-35090 in production — separate from our analysis above.

Notes0 Guidelines

Know something about CVE-2026-35090?

The advisory tells you what broke. It rarely tells you what actually worked. If you’ve dealt with this one, that detail is what the next engineer is searching for.

The version that genuinely resolved it — not the one the vendor claimed
A config change or rule that shut the vector down
A gotcha in the upgrade path that cost you an afternoon

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What this is

A place for practitioners to share what actually worked: a mitigation you’ve tested, a configuration change, a version- or environment-specific caveat, or a link to a verified patch. The most useful notes rise to the top as peers upvote them, so the signal stays high.

What belongs here

Verified mitigations, workarounds, and config changes
Version or environment caveats, and links to real fixes
No weaponised exploit code, or anything meant to cause harm
No spam, self-promotion, credentials, or personal data

At a glance

A fix existsA vendor remedy is published

Severity 9.3 Critical

Exploit likelihood EPSS, next 30 days 0.6%

Remediation

A high-priority fix

Have this fixed 18 hrs · Moderate

Typical engagement from $3,200

Get a fix See the full breakdown ↓

A high-priority vulnerability. Send your environment and a specialist will scope CVE-2026-35090 and return a fixed quote and timeline.

You’ll deal with our team directly and deploy the reviewed fix to staging first — never straight to production.

Official description Straight from the sourceThe vendor's or NVD's own wording, published unedited. Authoritative, but often terse — it says what broke, rarely what to do.

Technical summary Written by usOur analysis, written from the advisory, the CVSS vector and the affected-version data. It adds context the advisory leaves out, and never invents facts that are not in the source.

CVSS breakdown How the score is builtThe industry scoring standard. It rates how the flaw is reached, what it takes to exploit, and what an attacker gains — the score is derived from those, not the other way round.

Am I affected? How to checkSteps we derive from the advisory and the affected-version data, so you can decide whether this CVE reaches your setup. They are a guide, not a scan — your own configuration is the authority.

Check your environment

Remediation Closing itWhat it takes to close this. Where a vendor fix exists we point at it; where none exists we say so plainly, and can build one. Effort estimates are scoped from the advisory, not from your codebase.

Scan for this in your stack

References Go to the primary sourcePrimary sources — vendor advisories, patches and trackers. Where our summary and a reference disagree, the reference wins.

Practitioner notes

No notes yet

Official description

Technical summary

CVSS breakdown

Am I affected?

Remediation

References