Security readout for executives and security teams
Plain-English summary
CVE-2026-20421 is a MediaTek modem vulnerability that can crash a device’s modem when it connects to an attacker-controlled rogue base station. The business impact is availability loss, not data theft or code execution based on current sources. Exploitation requires local radio proximity and no user interaction.
Executive priority
Treat as a moderate-priority availability risk. Patch exposed mobile or embedded fleets through normal firmware channels, with higher urgency for personnel or assets operating in hostile or high-surveillance radio environments.
Technical view
MediaTek describes improper input validation in modem firmware, mapped to CWE-125, causing a possible system crash. CVSS 3.1 is 6.5 with adjacent attack vector, low complexity, no privileges, no user interaction, and high availability impact. Affected chipsets include listed MT27xx, MT68xx, and MT8791 models. Patch ID is MOLY01738293.
Likely exposure
Organizations using devices with the listed MediaTek chipsets may be exposed until OEM firmware incorporating the MediaTek patch is applied. Exposure is most relevant for mobile, IoT, or embedded fleets operating in areas where rogue base-station proximity is plausible.
Exploitation context
The source states exploitation requires a UE connected to a rogue base station controlled by the attacker. No additional privileges or user interaction are needed. The provided sources do not indicate known active exploitation, and the CVE is not marked KEV.
Researcher notes
Evidence is limited to the CVE record and MediaTek bulletin reference. The issue is described at a high level only; no protocol details, affected firmware branches, or OEM device mapping are provided in the supplied sources.
Mitigation direction
- Identify devices using the affected MediaTek chipsets.
- Check MediaTek’s February 2026 bulletin and OEM advisories for firmware availability.
- Prioritize firmware updates that include Patch ID MOLY01738293.
- For high-risk environments, review rogue base-station detection or cellular usage controls.
Validation and detection
- Inventory device models and map them to MediaTek chipset identifiers.
- Confirm vendor firmware notes reference CVE-2026-20421 or Patch ID MOLY01738293.
- Verify deployed firmware versions against OEM security bulletin guidance.
- Monitor device crash reports for modem-related instability in suspicious locations.
Public sources used
Generated from the cited source records. This long-tail analysis has not been individually reviewed by a named human.
Conservative CVE-to-ATT&CK context
These mappings and lookup hints may be relevant to the vulnerability behavior, CWE, affected product, or exposure path. Glexia-inferred context is not an official MITRE, ATT&CK, CWE, or CVE Program mapping.
ATT&CK lookup starting points
Use these exact CWE pages and searches to review the Glexia ATT&CK library from this CVE's weakness and description context.
CWE-125: Exact CWE lookup
Use the exact CWE identifier as the starting point before reviewing related ATT&CK behavior. Open the exact CWE lookup page first, then review the ATT&CK searches from that MITRE weakness context. This is a Glexia lookup hint, not an official ATT&CK mapping.
Open ATT&CK lookupCVE-2026-20421 mapping review
Open the CVE-to-ATT&CK bridge for reviewed, inferred, or future official mappings tied to this CVE.
Open ATT&CK lookup- Severity
- Medium
- CVSS
- 6.5 (3.1)
- Known Exploited
- No
- Published
Vector: CVSS:3.1/AV:A/AC:L/PR:N/UI:N/S:U/C:N/I:N/A:H
CNA and ADP enrichment extracted from CVE v5
These fields come from the CVE record and ADP containers, not from Glexia's Take. They preserve time-varying source decisions such as CISA SSVC, KEV status, CVSS metrics, and provider references.
CVSS vector scores
1 official scoreWe collect every scored CVSS vector available in the official CNA and ADP containers. When more than one version is present, the table keeps the source vectors side by side instead of collapsing them into the highest score.
CVSS:3.1/AV:A/AC:L/PR:N/UI:N/S:U/C:N/I:N/A:H2.83.6Primary CVE scoreVulnerability scoring details
Base CVSS 3.1 score
6.5MediumVector: CVSS:3.1/AV:A/AC:L/PR:N/UI:N/S:U/C:N/I:N/A:H
Source materials
- CVE List V5 sourceCVE List V5
- https://corp.mediatek.com/product-security-bulletin/February-2026CVE reference
Products and packages named in the record
CWE details
CWE links open Glexia weakness intelligence pages with official CWE context, developer remediation guidance, and related CVE mappings.
Out-of-bounds Read
Out-of-bounds Read represents a recurring weakness pattern that can create exploitable paths when design, validation, or implementation controls are missing.