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MediaTek Modem CVE-2026-20534

| EUVDEUVD-2026-92189 MEDIUM
Out-of-bounds Read (CWE-125)
2026-10-05 security@mediatek.com GHSA-vv5q-53j2-fq73
5.3
CVSS 3.1 · Vendor: mediatek
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Attack ChainAIDerived

Hypothetical attack flow derived from CVE metadata – not a confirmed exploit chain

  1. Access
    Deploy rogue base station in radio range
  2. Delivery
    Induce victim UE to camp on rogue cell
  3. Exploit
    Send malformed signaling message
  4. Execution
    Trigger out-of-bounds read in modem parser
  5. Impact
    Crash modem / deny cellular service

Vulnerability Assessment

Weakness
CWE
ASVS 5.0
V15 - Secure Coding and Architecture Bounds checking, read limits
MITRE ATT&CK

1 technique across 1 tactic: Collection

The technique list with ATT&CK links and the kill-chain view is part of the Basic plan and up.

Exploitation Conditions

Exploitation requires that the target UE (handset using an affected MediaTek modem) first connect to a rogue base station controlled by the attacker - i.e. the attacker must operate a malicious cellular cell within radio range and get the victim device to camp on it (reflected as AV:A, adjacent, and AC:H). No authentication and no user interaction are required once that association occurs (PR:N/UI:N). Impact is limited to availability (A:H, modem denial of service) with no confidentiality or integrity effect (C:N/I:N). Realistic limiting factors for defenders: the need for physical radio proximity and a functioning rogue base station, the absence of any confirmed in-the-wild exploitation (SSVC Exploitation=none), non-automatable exploitation (SSVC Automatable=no), and applicability only to the enumerated MediaTek chipset models running vulnerable modem firmware.

Impact

This is a genuine-but-bounded issue, not a top-priority emergency. The input CVSS of 5.3 (CVSS:3.1/AV:A/AC:H/PR:N/UI:N/S:U/C:N/I:N/A:H) correctly captures the profile: adjacent attack vector (not true network/Internet reach), high attack complexity, no privileges or user interaction, and availability-only impact (C:N/I:N - no confidentiality or integrity loss). The limiting factor is that the victim UE must first associate with an attacker-controlled rogue base station, which is why AV:A and AC:H are appropriate rather than AV:N. All corroborating exploitation signals point the same direction and reinforce low urgency: CISA SSVC reports Exploitation=none, Automatable=no, Technical Impact=partial; there is no CISA KEV listing and no public exploit identified at time of analysis. No EPSS score was provided in the input, so probabilistic exploitation likelihood cannot be quoted. The signals are internally consistent - there is no CVSS-versus-reality conflict here - though note a tagging discrepancy: the input carries 'Buffer Overflow' and 'Information Disclosure' tags, yet the CWE is CWE-125 (out-of-bounds READ, not an overflow/write) and the CVSS sets C:N, so no confidentiality/information-disclosure impact is actually claimed by the vendor scoring. Treat this as a localized radio-proximity denial-of-service risk against MediaTek modem firmware, prioritized via normal mobile OTA/vendor patch cycles rather than emergency response.

Exploit ScenarioDerived

An attacker stands up a rogue cellular base station (false base station / IMSI-catcher style cell) in physical radio proximity to victims and induces nearby MediaTek-modem handsets to camp on it. The attacker then transmits a malformed signaling/protocol message that the modem parses with an incorrect bounds check, triggering an out-of-bounds read that crashes the modem and denies cellular service. No public exploit code or PoC was identified in the provided intelligence, and SSVC marks exploitation as none.

This Month Plan within 30 days. Why: MEDIUM severity (CVSS 4.0-6.9).
No patch listed yet 0.2% exploitation probability (EPSS)

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AnalysisAIv1 – Oct 05, 2026

Modem denial of service in MediaTek baseband firmware allows an attacker operating a rogue base station within radio range to crash or reset a victim handset's modem through an out-of-bounds read (CWE-125) caused by an incorrect bounds check on attacker-influenced over-the-air data. The attacker must first get the target UE to camp on the malicious cell (CVSS 3.1 AV:A/AC:H), after which no privileges and no user interaction are required, and the only impact is loss of availability of the modem (A:H, C:N/I:N), yielding a 5.3 base score. There is no public exploit identified at time of analysis, CISA's SSVC assessment records Exploitation=none and Automatable=no, and applicability is limited to devices built on the enumerated MediaTek chipset models with vulnerable modem firmware, so this is a genuine but bounded, proximity-dependent availability risk rather than a mass-exploitation emergency.

RemediationAI

Vendor-released patch: apply the modem/baseband fix identified by MediaTek patch ID MOLY01797547 (issue MSV-9155), distributed through the MediaTek Product Security Bulletin for October 2026 (https://www.mediatek.com/product-security-bulletin/October-2026). Since this is chipset-level firmware, the fix reaches end users only via OEM/device-vendor or carrier firmware updates, so fleet owners should track their handset, module and CPE vendors' advisories and require confirmation that MOLY01797547 is included in the build; for devices that cannot be updated, treat them as unpatched for this issue. Because exploitation requires a rogue base station in radio range, the most effective compensating controls are on the network side rather than the device: enforce subscriber/network mutual authentication (5G AKA, or the strongest authentication the carrier supports), enable and monitor the carrier's or operator's rogue-base-station/IMSI-catcher detection so anomalous cells are flagged or blocked, and - where the device management profile allows it and coverage requirements permit - restrict automatic attachment to untrusted or non-authenticated cells. The trade-offs are real: disabling legacy radio modes or tightening cell-selection policies can reduce coverage, roaming or emergency-service reachability, and network-side detection does not help a device that is already camped on the attacker's cell, so firmware remediation remains the only complete fix. Given SSVC Exploitation=none, Automatable=no and the absence of public exploit code or KEV listing, remediation can follow a normal patch cycle, prioritized for high-value or physically exposed users (executives, field personnel, high-security sites) where rogue-cell activity is plausible.

Affected VersionsENISA

MediaTek chipset MT6982
MediaTek chipset MT6993
MediaTek chipset MT8675
MediaTek chipset MT8678
MediaTek chipset MT8795T
MediaTek chipset MT6897
MediaTek chipset MT6893
MediaTek chipset MT8768
MediaTek chipset MT6989
MediaTek chipset MT6768
MediaTek chipset MT8781
MediaTek chipset MT8792
MediaTek chipset MT6763
MediaTek chipset MT6875
MediaTek chipset MT6883
MediaTek chipset MT2737
MediaTek chipset MT6815
MediaTek chipset MT6783
MediaTek chipset MT6885
MediaTek chipset MT8666
MediaTek chipset MT6761
MediaTek chipset MT6881
MediaTek chipset MT2735
MediaTek chipset MT6889
MediaTek chipset MT8883
MediaTek chipset MT8788E
MediaTek chipset MT6886
MediaTek chipset MT6785
MediaTek chipset MT8873
MediaTek chipset MT6895
MediaTek chipset MT6762
MediaTek chipset MT6858
MediaTek chipset MT6771
MediaTek chipset MT6988
MediaTek chipset MT8788
MediaTek chipset MT2716
MediaTek chipset MT6769
MediaTek chipset MT6980
MediaTek chipset MT6813
MediaTek chipset MT6878
MediaTek chipset MT6853
MediaTek chipset MT8765
MediaTek chipset MT8797
MediaTek chipset MT6990
MediaTek chipset MT8771
MediaTek chipset MT6855
MediaTek chipset MT6986
MediaTek chipset MT6899
MediaTek chipset MT6879
MediaTek chipset MT8755
MediaTek chipset MT6890
MediaTek chipset MT6739
MediaTek chipset MT6891
MediaTek chipset MT8676
MediaTek chipset MT8673
MediaTek chipset MT6833
MediaTek chipset MT6765
MediaTek chipset MT8786
MediaTek chipset MT6880
MediaTek chipset MT6767
MediaTek chipset MT8798
MediaTek chipset MT6983
MediaTek chipset MT6896
MediaTek chipset MT6991
MediaTek chipset MT8766
MediaTek chipset MT6985
MediaTek chipset MT8668
MediaTek chipset MT8766R
MediaTek chipset MT6789
MediaTek chipset MT6835
MediaTek chipset MT8667
MediaTek chipset MT8893
MediaTek chipset MT8791T
MediaTek chipset MT8863
MediaTek chipset MT6779
MediaTek chipset MT8789
MediaTek chipset MT8775
MediaTek chipset MT8793
MediaTek chipset MT6877
MediaTek chipset MT6781
MediaTek chipset MT8791
MediaTek chipset MT6873
MediaTek chipset MT8796

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Technical ContextAI · show details

The flaw is an out-of-bounds read (CWE-125) in the modem/baseband component of MediaTek chipsets: a length or offset derived from data received over the radio interface is validated incorrectly, letting the modem firmware read past the end of an intended buffer. Because the input path is the cellular air interface rather than an IP socket, the practical attack surface is the base station side of the link - the attacker must run a rogue cell (a fake eNodeB/gNodeB-style setup) and induce the UE to attach to it, which is why the assessed vector is adjacent (AV:A) with high attack complexity (AC:H): the attacker needs both physical radio proximity and the victim device to select the malicious cell. No credentials (PR:N) and no user action (UI:N) are needed once that association is established. The scanning-context tags (Buffer Overflow, Denial Of Service, Information Disclosure) reflect the memory-safety class of the bug, but the independently assessed impact is availability-only - the out-of-bounds read manifests as a modem crash/reset rather than a demonstrated confidentiality or integrity compromise, hence C:N/I:N/A:H. Fixes are delivered as baseband/modem firmware patches (patch ID MOLY01797547, issue MSV-9155) that must be propagated by MediaTek's chipset customers into device firmware.

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Severity by source

Vendor (mediatek) PRIMARY 5.3 MEDIUM
AV:A/AC:H/PR:N/UI:N/S:U/C:N/I:N/A:H
vuln.today AI 5.3 MEDIUM

Adjacent radio vector (AV:A) with AC:H because the victim must camp on an attacker's rogue base station; no auth or interaction (PR:N/UI:N); out-of-bounds read yields availability-only impact (A:H, C:N/I:N).

3.1 AV:A/AC:H/PR:N/UI:N/S:U/C:N/I:N/A:H
4.0 AV:A/AC:L/AT:P/PR:N/UI:N/VC:N/VI:N/VA:H/SC:N/SI:N/SA:N

Primary rating from Vendor (mediatek).

CVSS VectorVendor: mediatek

Attack Vector
Adjacent
Attack Complexity
High
Privileges Required
None
User Interaction
None
Scope
Unchanged
Confidentiality
None
Integrity
None
Availability
High

Lifecycle Timeline

3
CVSS changed
Oct 05, 2026 - 11:22 NVD
5.3 (None) 5.3 (MEDIUM)
CVE Published
Oct 05, 2026 - 02:16 cve.org
MEDIUM 5.3
CVE Published
Oct 05, 2026 - 02:16 cve.org
UNKNOWN (no severity yet)

DescriptionCVE.org

In Modem, there is a possible out of bounds read due to an incorrect 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: MOLY01797547; Issue ID: MSV-9155.

Threat Intelligence Overview

EPSS Score
0.2%
Top 93% exploitable
Prevalence
High
MediaTek modems power a very large share of global Android smartphones
Data Quality
5 sources
Confidence: Medium

How this decision was reached

The engine reads each signal below and applies a fixed list of rules from top to bottom. The first rule that matches sets the recommended action – like a statement, every line is shown.

SignalValue
Severity MEDIUM
CISA KEV No
Public POC No
EPSS 0.2%
Patch available No
Active threat No
Deciding rule
MEDIUM severity (CVSS 4.0-6.9)
What every action level means
Emergency Immediate action required. Criteria: CRITICAL + in CISA KEV (actively exploited) without patch, OR CRITICAL + EPSS > 30% without patch, OR CRITICAL + active threat signals without patch.
Act Now Prioritize within 24-48h. Criteria: in KEV with patch available, OR CRITICAL + public POC, OR HIGH + EPSS > 10%, OR CRITICAL + active threat, OR any CRITICAL severity.
This Week Schedule remediation this week. Criteria: HIGH severity (CVSS 7.0-8.9). Patch within normal change window.
This Month Plan within 30 days. Criteria: MEDIUM severity (CVSS 4.0-6.9), lower exploitation probability. Include in regular patch cycle.
Monitor Track and reassess. Criteria: LOW severity (CVSS 0.1-3.9), minimal exploitation risk. No immediate action needed.

SSVC AssessmentENISA

SSVC Decision· derived
Scheduled
Exploitation
None
System Exposure· derived
Controlled
Automatable
No
Human Impact· derived
High
Technical Impact
Partial

Priority Score

26
Low Medium High Critical
KEV: 0
EPSS: 0
CVSS: +26
PoC: 0
Weaponized: 0
Threat intel: 0
Gov advisory: 0

Attack Technique

A buffer overflow occurs when a program writes more data to a memory buffer than it was allocated to hold, causing the excess data to spill into adjacent memory regions.

Information disclosure occurs when an application unintentionally exposes sensitive data that aids attackers in reconnaissance or directly compromises security.

Denial of Service attacks render applications or systems unavailable by overwhelming resources or triggering failure conditions.

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