dbcve.org
Nr15Operating system · Mediatek

CVE-2026-20403

MEDIUM · 6.5 CVSS v3.1 Published 2026-02-02
Mitigation only
No fix yet — a mitigation exists. There is no fixed release. A documented workaround reduces exposure in the meantime.
See remediation →
70/100
Remediation priority · Elevated
No privileges Zero-click

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.

NVD · unedited
In Modem, there is a possible system crash due to a missing bounds check. This could lead to remote denial of service, if a UE has connected to a rogue base station controlled by the attacker, with no additional execution privileges needed. User interaction is not needed for exploitation. Patch ID: MOLY01689254 (Note: For N15 and NR16) / MOLY01689259 (Note: For NR17 and NR17R); Issue ID: MSV-4843.

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.

dbcve analysis · high confidence

A missing bounds check in the modem firmware allows a rogue base station to trigger a system crash via malformed communications. When User Equipment (UE) connects to an attacker-controlled base station, the modem fails to validate input bounds properly, causing a denial of service condition. No user interaction or elevated privileges are required beyond connecting to the malicious network.

MitigationApply the vendor-provided patches (MOLY01689254 for N15/NR16, MOLY01689259 for NR17/NR17R) to the modem firmware. Until the patch is deployed, advise users to avoid connecting to untrusted or unknown base stations.

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

Affected products & versions What the vendor confirmedThe version ranges the vendor confirmed as vulnerable. If your version sits inside a range here, treat yourself as exposed until you have upgraded.

NVD · CPE data
Nr15Operating system
Affected:all versions
Nr16Operating system
Affected:all versions
Nr17Operating system
Affected:all versions
Nr17rOperating system
Affected:all versions

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.

From the vector
Attack vector
Adjacent
Complexity
Low
Privileges
None
User interaction
None
Scope
Unchanged
Confidentiality
None
Integrity
None
Availability
High

CVSS:3.1/AV:A/AC:L/PR:N/UI:N/S:U/C:N/I:N/A:H

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.

dbcve checks

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

  1. Identify Mediatek modem presence
    Query the modem for its model information using AT commands such as 'ATI' or check system device information for Mediatek NR15, NR16, NR17, or NR17r modem chips
    Affected if The device contains any of these Mediatek modem variants (Nr15, Nr16, Nr17, Nr17r)
  2. Check modem firmware version
    Retrieve the firmware version using AT command 'AT+CGMR' or 'AT+CGMM' and compare against the patched versions (MOLY01689254 for N15/NR16, MOLY01689259 for NR17/NR17R)
    Affected if The installed firmware version is earlier than the patched build numbers or if the specific patch identifiers are not present in the firmware metadata
  3. Verify patch deployment status
    Check the modem firmware build properties or release notes for the presence of patch identifiers MOLY01689254 or MOLY01689259 depending on the modem variant identified in step 1
    Affected if Neither patch identifier is found in the firmware, indicating the vulnerability remains unpatched
  4. Confirm network exposure
    Review system or network logs for any unexpected base station connections or monitor for crash reports related to modem communications
    Affected if The device has connected to or is capable of connecting to untrusted or unknown cellular base stations without operator-controlled network isolation

A device is affected if it contains any Mediatek Nr15, Nr16, Nr17, or Nr17r modem firmware that lacks the corresponding vendor patch (MOLY01689254 or MOLY01689259) and operates in an environment where connection to untrusted base stations is possible.

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

Check your environment

Paste your version and any relevant configuration and it will be compared against the affected criteria above. Do not include secrets or credentials.

AI-assisted, checked against the advisory. Informational, not a guarantee.

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.

From vendor data
Mitigation available No clean upgrade yet — mitigate in the meantime
Mitigation

Apply the vendor-provided patches (MOLY01689254 for N15/NR16, MOLY01689259 for NR17/NR17R) to the modem firmware. Until the patch is deployed, advise users to avoid connecting to untrusted or unknown base stations.

Fix this in Nr15 Scoped from the published advisory
  • Consultation2.0 h
  • Implementation4.0 h
  • Testing6.0 h
  • Review / QA3.0 h
15.0 hours of engineering $2,560
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References Go to the primary sourcePrimary sources — vendor advisories, patches and trackers. Where our summary and a reference disagree, the reference wins.

Primary sources

Practitioner notes

Contributed

Peer-ranked notes from engineers who’ve handled CVE-2026-20403 in production — separate from our analysis above.

No notes yet

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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
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  • Version or environment caveats, and links to real fixes
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