CVE-2026-20434
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 · uneditedIn Modem, there is a possible out of bounds write due to a missing bounds check. This could lead to remote escalation of privilege, if a UE has connected to a rogue base station controlled by the attacker, with no additional execution privileges needed. User interaction is needed for exploitation. Patch ID: MOLY00782946; Issue ID: MSV-4135.
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 confidenceAn out-of-bounds write vulnerability exists in Modem firmware due to a missing bounds check. An attacker controlling a rogue base station can exploit this to achieve remote privilege escalation on a User Equipment (UE) device that connects to the malicious network, requiring user interaction to initiate the connection.
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 dataall versionsall versionsall versionsall versionsall versionsCVSS 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
- High
- Privileges
- None
- User interaction
- None
- Scope
- Unchanged
- Confidentiality
- High
- Integrity
- High
- Availability
- High
CVSS:3.1/AV:A/AC:H/PR:N/UI:N/S:U/C:H/I:H/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 checksWork through these to decide whether this CVE applies to you.
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Identify the modem chipset modelQuery the modem via AT commands (e.g., AT+CGMM, AT+CGMI) or check system logs/dmesg for Mediatek modem driver information to determine if the chipset is one of: Lr12a, Lr13, Nr15, Nr16, or Nr17Affected if The chipset matches any of the listed models (Lr12a, Lr13, Nr15, Nr16, Nr17)
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Check the installed modem firmware versionUse AT commands such as AT+CGMR or ATI to retrieve the firmware version string from the modem; alternatively, check the device system info or modem firmware binary metadataAffected if The firmware version is present and corresponds to Mediatek modem firmware (all versions of these chipsets are affected)
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Verify the device has cellular connectivity enabledCheck if the cellular radio/modem is powered on and registered to a network using AT+CREG? or by inspecting network interface status (e.g., rmnet, ccmni interfaces)Affected if Cellular connectivity is active and the device can connect to base stations
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Inspect recent network registration eventsReview modem logs, network logs, or use AT+CNCI to list network carrier information; look for connection attempts or registrations to unknown or untrusted base stationsAffected if The device has connected to or attempted to connect to a cellular network that is not a known trusted operator
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Review user-initiated network selection settingsCheck if the device is configured for manual network selection (AT+CNMP=2) rather than automatic (AT+CNMP=1), or inspect user-configured preferred network listsAffected if The device allows or has historically connected to manually selected networks, increasing exposure to rogue base stations
A device is affected if it uses any Mediatek Lr12a, Lr13, Nr15, Nr16, or Nr17 modem chipset with cellular connectivity enabled, regardless of firmware version, and an attacker could induce a user to connect to a rogue base station to trigger the out-of-bounds write.
Generated from the published advisory. Verify against your own configuration.
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 dataApply the vendor patch (MOLY00782946) to update Modem firmware; advise users to avoid connecting to untrusted or unknown cellular networks.
- Consultation8.0 h
- Implementation16.0 h
- Testing24.0 h
- Review / QA8.0 h
An estimate, not a bill — we confirm scope with you before any work starts. Need it this week? Rush from $15,232.
Scan for this in your stack
Free · runs locallyCheck whether your project pulls in CVE-2026-20434 — or any other known-vulnerable package — straight from your lock files. Free and open source; it runs locally and uploads nothing.
References Go to the primary sourcePrimary sources — vendor advisories, patches and trackers. Where our summary and a reference disagree, the reference wins.
Primary sourcesPractitioner notes
ContributedPeer-ranked notes from engineers who’ve handled CVE-2026-20434 in production — separate from our analysis above.
The advisory tells you what broke. It rarely tells you what actually worked. If you’ve dealt with this one, that detail is what the next engineer is searching for.
- The version that genuinely resolved it — not the one the vendor claimed
- A config change or rule that shut the vector down
- A gotcha in the upgrade path that cost you an afternoon
No notes yet
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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.
- Verified mitigations, workarounds, and config changes
- Version or environment caveats, and links to real fixes
- No weaponised exploit code, or anything meant to cause harm
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