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MediaTek Modem EUVDEUVD-2026-92183

| CVE-2026-20540 MEDIUM
Buffer Over-read (CWE-126)
2026-10-05 security@mediatek.com GHSA-qcwv-wm5j-jgj5
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 near target
  2. Delivery
    Induce victim UE to attach
  3. Exploit
    Send malformed radio-layer message
  4. Execution
    Trigger out-of-bounds read in modem
  5. Impact
    Baseband crash denies cellular service

Vulnerability Assessment

Weakness
CWE
ASVS 5.0
V15 - Secure Coding and Architecture Buffer over-read prevention
Exploitation Conditions

Exploitation requires the attacker to operate a rogue/malicious base station and to get the victim UE to connect to it over the cellular radio interface - this adjacent-network precondition (AV:A) plus the setup effort is precisely what drives the high attack complexity (AC:H). No authentication (PR:N) and no user interaction (UI:N) are needed once the device has attached. The limiting factors are substantial: the attacker needs specialized radio hardware, physical proximity to the target, and successful victim attachment to the rogue cell; the impact is confined to denial of service (baseband crash), with no code execution, data disclosure, or integrity compromise. Affected scope is MediaTek modem firmware across the listed chipsets (e.g., MT6765, MT6883, MT6991, MT8798).

Impact

This is a genuine-but-moderate issue, correctly rated medium (CVSS 5.3). The CVSS vector CVSS:3.1/AV:A/AC:H/PR:N/UI:N/S:U/C:N/I:N/A:H is internally consistent with the description: exploitation occurs over the radio interface (AV:A - adjacent, not true network/Internet reach), requires no authentication (PR:N) and no user interaction (UI:N), but carries high attack complexity (AC:H) because the attacker must stand up a rogue base station AND induce the victim UE to attach to it. Impact is availability-only (A:H, a denial of service) with no confidentiality or integrity loss (C:N/I:N) - consistent with CWE-126 (out-of-bounds/buffer over-read). The SSVC framework reinforces a low-urgency posture: Exploitation=none (no observed activity), Automatable=no (each attack requires physical radio proximity and victim attachment, so it cannot be scripted at scale), Technical Impact=partial. There is no KEV listing and no public POC, and no EPSS score was supplied - absence of EPSS is a data gap, not evidence either way. All signals align: this is a real but low-priority defect - a targeted, proximity-bound DoS rather than a wormable or remotely weaponizable flaw. Priority should be routine patch-cycle remediation, not emergency response.

Exploit ScenarioDerived

An attacker deploys a rogue/IMSI-catcher-style base station near a target and tricks a nearby MediaTek-modem device into attaching to it. The attacker then sends a crafted malformed radio-layer message that triggers an out-of-bounds read in the modem firmware, crashing the baseband and denying cellular service to the victim. No public exploit code is known, and the attack requires both specialized radio equipment and physical proximity.

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

Remote denial of service against MediaTek modem (baseband) firmware affects more than 80 chipsets - including MT6765, MT6785, MT6833, MT6883, MT6985, MT6991 and MT8798 - where a missing bounds check during cellular message parsing produces an out-of-bounds read (CWE-126) that can crash the baseband. An attacker who operates a rogue base station and gets a victim UE to attach can trigger the fault with no authentication (PR:N) and no user interaction (UI:N), though the adjacent-network position and specialized radio hardware required drive the high attack complexity (AC:H) and the CVSS 3.1 score of 5.3, with impact limited to availability. Neither our independent assessment nor CISA's SSVC framework records known exploitation (Exploitation: none, Automatable: no), so no public exploit is identified at time of analysis.

RemediationAI

Vendor-released patch: Patch ID MOLY01774038 (MediaTek Product Security Bulletin, October 2026 - https://www.mediatek.com/product-security-bulletin/October-2026); OEMs and module vendors must incorporate this baseband firmware fix into device updates, so the practical action for enterprises is to track firmware updates from their handset, tablet, IoT and CPE suppliers and treat the modem stack as part of the patchable attack surface. Until firmware is applied, user-level mitigation is limited because the fault is reached over the radio interface; the most effective compensating control is to avoid attaching to untrusted or suspicious cells, and where deployment policy permits, disable or deprioritize legacy RATs (for example 2G/GSM) that are easiest for a rogue base station to impersonate - with the trade-off that coverage, roaming and some IoT connectivity may be lost. Mobile network operators can reduce exposure by deploying false-base-station and RRC/NAS anomaly detection, accepting the operational cost and residual false-positive rate of that monitoring. Physically isolating radio hardware (modem sandboxing, airplane mode) prevents the attack entirely but removes cellular service, and is only practical for high-assurance or forensic use cases; there is no configuration setting that hardens the vulnerable message parser itself.

Affected VersionsENISA

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

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Technical ContextAI · show details

The flaw sits in MediaTek modem firmware that parses over-the-air cellular signaling (the baseband stack handling the radio interface between UE and network) and is classified as CWE-126, buffer over-read, caused by a missing bounds check on a length or index field before memory is read. Rather than corrupting memory or enabling code execution, the unchecked read can pull data past the end of an allocated buffer, which in a baseband processor typically manifests as an assertion, watchdog reset, or crash of the modem subsystem. The CVSS 3.1 vector AV:A/AC:H/PR:N/UI:N/S:U/C:N/I:N/A:H confirms the exploit path is adjacent-network (the rogue base station the UE associates with), unauthenticated and interaction-free once attachment occurs, but with high complexity and no confidentiality or integrity impact. Affected hardware spans MediaTek's smartphone, tablet, IoT and CPE silicon families listed in the EUVD record; the advisory reference is MediaTek's October 2026 Product Security Bulletin.

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  • Exploit and PoC references, threat intelligence from 22 sources

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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

AV:A and AC:H because exploitation needs a rogue base station the victim must attach to; PR:N/UI:N per description; impact is DoS only, so C:N/I:N/A:H.

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 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: MOLY01774038; Issue ID: MSV-8912.

Threat Intelligence Overview

EPSS Score
0.2%
Top 93% exploitable
Prevalence
High
MediaTek is a top global smartphone baseband vendor; chipsets ship in vast numbers
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.

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

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