Security readout for executives and security teams
Plain-English summary
CVE-2026-20405 is a MediaTek modem flaw that can crash affected devices when they connect to an attacker-controlled rogue base station. The impact described is denial of service, not data theft or code execution. Practical risk is highest for devices using listed MediaTek chipsets in environments where rogue cellular base stations are plausible.
Executive priority
Treat as a targeted availability risk. It is unlikely to be mass-exploited remotely over the internet, but could disrupt affected devices near hostile cellular infrastructure. Prioritize asset identification and firmware coordination for critical mobile or embedded deployments.
Technical view
The issue is a missing bounds check in MediaTek modem firmware, associated with CWE-617. CVSS 3.1 is 6.5, with adjacent-network attack vector, no privileges, no user interaction, and high availability impact. MediaTek identifies Patch ID MOLY01688495 and Issue ID MSV-4818. Affected chipset models are listed in the CVE record and MediaTek bulletin.
Likely exposure
Exposure depends on whether an organization owns devices containing the listed MediaTek chipsets and whether vendors have shipped firmware incorporating MediaTek’s fix. This is not broadly internet-reachable; the CVSS vector and description require proximity through a rogue base station scenario.
Exploitation context
Sources state exploitation requires a UE connected to a rogue base station controlled by the attacker. No user interaction or privileges are needed. The provided sources do not report active exploitation, and the CVE is not listed as KEV in the supplied bundle.
Researcher notes
Evidence is limited to the CVE record and MediaTek bulletin metadata. Sources identify affected chipset families and a patch ID, but do not provide fixed firmware versions, OEM rollout status, or proof-of-concept details. Avoid assuming all devices with these chipsets are patched without OEM confirmation.
Mitigation direction
- Inventory mobile, IoT, tablet, and embedded devices for listed MediaTek chipsets.
- Check OEM and carrier firmware advisories for updates containing MediaTek Patch ID MOLY01688495.
- Prioritize updates for devices used in high-risk locations or sensitive operations.
- If no update is available, ask the device vendor for remediation timelines.
Validation and detection
- Confirm whether assets contain affected MediaTek chipset models listed in the CVE.
- Record current baseband, modem, or device firmware versions where available.
- Verify vendor firmware notes reference CVE-2026-20405 or Patch ID MOLY01688495.
- Monitor MediaTek and OEM advisories for updated affected-version or fix information.
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-617: 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-2026-20405 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.
Reachable Assertion
Reachable Assertion represents a recurring weakness pattern that can create exploitable paths when design, validation, or implementation controls are missing.