CVE-2026-20556 MediaTek, Inc. CVE debrief

Who should care

Defenders responsible for Modem or related systems should assess exposure and prioritize verification of affected versions and remediation guidance from official sources. This includes operators, platform administrators, vulnerability management teams, and security teams who need to review and apply patches or mitigations to prevent potential remote escalation of privilege. They should also review compensating controls for exposed systems while remediation

Why it matters

CVE-2026-20556 is a possible out of bounds write in Modem due to a missing bounds check. Defenders should prioritize verification of affected versions and remediation guidance from official sources to prevent potential remote escalation of privilege.

• Remote escalation of privilege possible if UE connects to rogue base station
• Requires verification of affected versions and systems
• Patch application recommended if available

Technical summary

A possible out of bounds write in Modem due to a missing bounds check could lead to remote escalation of privilege if a UE has connected to a rogue base station controlled by the attacker. This vulnerability affects Modem and could be exploited without additional execution privileges needed. User interaction is not needed for exploitation. The CVE record indicates that the Patch ID is MOLY01876662 and the Issue ID is MSV-9833. Defenders should prioritize verification of affected versions and remediation guidance from official sources.

Defensive priority

Defenders should prioritize verification of affected versions and remediation guidance from official sources.

Recommended defensive actions

• Verify affected versions and systems
• Review and apply patch if available
• Monitor for potential exploitation attempts
• Confirm whether affected product deployments exist in managed environments and assign an owner for follow-up
• Review the supplied official advisory or CVE record to validate affected scope, severity, and vendor guidance
• Plan vendor-supported updates or mitigations through normal change control where exposure is confirmed
• Check relevant monitoring, detection, and logs for exposed assets that need extra review

Evidence notes

The CVE record indicates a possible out of bounds write in Modem due to a missing bounds check, which could lead to remote escalation of privilege if a UE has connected to a rogue base station controlled by the attacker.

Sources and references

Methodology and review provenance

AI-assisted synthesis based on stored public vulnerability evidence. System validation, approval state, and publication status do not by themselves establish human review of this revision. PatchSiren helps prioritize defensive review and does not prove exposure or remediation on any system.