Security readout for executives and security teams
Plain-English summary
CVE-2026-20403 is a MediaTek modem flaw that can crash affected devices when they connect to an attacker-controlled rogue base station. It does not require user interaction or device privileges. The business impact is availability disruption for devices using listed MediaTek chipsets, not data theft or code execution based on current sources.
Executive priority
Treat as a moderate availability risk. Prioritize environments where device uptime matters and devices may operate in untrusted radio environments. This is not currently evidenced as exploited in the wild, but remediation should follow normal firmware update cycles for affected fleets.
Technical view
The issue is a missing bounds check in the modem, categorized as CWE-787. CVSS 3.1 is 6.5 with adjacent attack vector, low complexity, no privileges, no user interaction, and high availability impact only. MediaTek lists patch IDs MOLY01689254 for N15/NR16 and MOLY01689259 for NR17/NR17R.
Likely exposure
Exposure is limited to devices using the listed MediaTek chipsets and modem software branches identified by MediaTek. The attacker must control a rogue base station near the user equipment. Asset owners usually need OEM device firmware information to confirm whether the relevant MediaTek modem patch is included.
Exploitation context
The source states remote denial of service is possible after a UE connects to a rogue base station. No public source in the bundle states active exploitation, and KEV is false. The practical risk is location-dependent disruption where rogue radio infrastructure is feasible.
Researcher notes
The bundle does not provide deeper protocol details, affected firmware versions, or OEM device mappings. Analysis should focus on chipset presence, modem branch applicability, and whether downstream firmware incorporates the named MediaTek patch IDs. Avoid assuming all devices with these chipsets are exposed without OEM confirmation.
Mitigation direction
- Review MediaTek February 2026 bulletin and relevant OEM firmware advisories.
- Apply firmware updates containing MOLY01689254 or MOLY01689259 where applicable.
- Prioritize managed mobile, IoT, automotive, or embedded devices using listed chipsets.
- If no OEM update is available, request remediation timing from the device vendor.
Validation and detection
- Inventory devices and map models to MediaTek chipsets listed in the bulletin.
- Confirm installed firmware includes the applicable MediaTek patch ID.
- Check vendor advisories for N15, NR16, NR17, or NR17R modem branch relevance.
- Monitor fleet telemetry for unexplained modem resets or network-triggered device crashes.
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-787: 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-2026-20403 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 Write
Out-of-bounds Write represents a recurring weakness pattern that can create exploitable paths when design, validation, or implementation controls are missing.